Author Topic: solar panel installation  (Read 65384 times)

Faraday

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Re: solar panel installation
« Reply #150 on: October 29, 2015, 03:02:47 PM »
1) I think your panels are on your roof, right? What kind of roof structure do you have - is it rafters or trusses?
2) Were there any special challenges your installers had with your roof?

3) You have a net-meter, right? And did it have to be installed, by the power company, BEFORE your array came online? Do you have to pay a monthly base surcharge for that meter? My power provider requires a $3/month charge for the dual-reading net meter.

1) I have rafters. The panels just screw into the shingles and the plywood under the shingles, no concern with connecting to a rafter or truss.
2) No problems that I'm aware of. My installation crew had about 6 people and did 12 panels in 4 hours. Got there first thing in the morning and were gone by lunch and I'm sure they did another install after lunch.
3) When the system was installed it was all ready except for a they had installed a second meter box but no meter. I had to wait a couple weeks for the power company to come out and put the second meter in the box and replace the old meter with a new "net" meter. This new meter measured power generated by the panels and the net meter measured net power usage by my home (usage - generated). I do not pay any additional fee for that second meter currently.

Thank you nawhite, that's super info, much appreciated. It's impressive as hell to me that 6 people got 12 panels installed in 4 hours. That sounds like they were very experienced and knew their roles well.

I'm guessing you have microinverters on each solar panel, so that all they had to do was pull an AC conduit, add a disconnect switch and route the line to an empty breaker in your external breaker box?

nawhite

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Re: solar panel installation
« Reply #151 on: November 01, 2015, 05:04:06 PM »
I'm guessing you have microinverters on each solar panel, so that all they had to do was pull an AC conduit, add a disconnect switch and route the line to an empty breaker in your external breaker box?

Not micro inverters, just one big one. Made it so they just had to plug them in series and one conduit for the return. It also helped that they could install them all on one big mounting rail all in a line. Made it simple.

Faraday

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Re: solar panel installation
« Reply #152 on: November 01, 2015, 09:22:46 PM »
I'm guessing you have microinverters on each solar panel, so that all they had to do was pull an AC conduit, add a disconnect switch and route the line to an empty breaker in your external breaker box?

Not micro inverters, just one big one. Made it so they just had to plug them in series and one conduit for the return. It also helped that they could install them all on one big mounting rail all in a line. Made it simple.

Wait, wait: so you had the rails pre-installed on the roof for the solar installers?

nawhite

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Re: solar panel installation
« Reply #153 on: November 02, 2015, 12:30:19 PM »
I'm guessing you have microinverters on each solar panel, so that all they had to do was pull an AC conduit, add a disconnect switch and route the line to an empty breaker in your external breaker box?

Not micro inverters, just one big one. Made it so they just had to plug them in series and one conduit for the return. It also helped that they could install them all on one big mounting rail all in a line. Made it simple.

Wait, wait: so you had the rails pre-installed on the roof for the solar installers?

No, sorry I don't have pictures. But take a look at Sol's pictures from near the start of the thread http://forum.mrmoneymustache.com/welcome-to-the-forum/solar-panel-installation/msg354102/#msg354102. Sol has 4 rows of 7 panels each. Mine has 1 row of 12 panels. And mine are rotated 90 degrees compared to Sol's so there are just two rails on the roof instead of 14. Made the install really easy for the installers.

Faraday

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Re: solar panel installation
« Reply #154 on: November 02, 2015, 12:51:03 PM »
No, sorry I don't have pictures. But take a look at Sol's pictures from near the start of the thread http://forum.mrmoneymustache.com/welcome-to-the-forum/solar-panel-installation/msg354102/#msg354102. Sol has 4 rows of 7 panels each. Mine has 1 row of 12 panels. And mine are rotated 90 degrees compared to Sol's so there are just two rails on the roof instead of 14. Made the install really easy for the installers.

Thank you nawhite. If I understand you correctly, your rails are oriented the way I expect to do them at my place, horizontally. The panels will be oriented vertically.

sol

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Re: solar panel installation
« Reply #155 on: March 09, 2016, 08:24:45 PM »
After almost 18 months of operation, our solar panels appear to be generating a net surplus of ~5200 kWh per year, measured as a running annual average.  That's net surplus on top of what our household actually uses (about another 5000 kWh/year).

We just bought a Nissan Leaf all-electric car.  If it drives 1000 miles/month at 3.9 kWh/mile, it will use 256 kWh of electricity at a cost of 7.41 cents per kWh.  That works out to 1.9 cents per mile, or $19/mo.  In a year of driving, the Leaf should use about 3000 kWh and cost us $230 in electricity.

So if our solar panels are already generating 5200 kWh of surplus energy, and the car is going to consume about 3000 kWh of that, then on an annual basis our panels should still generate more power than our house and car together will use.  We're approaching net zero.

Before the Leaf, our panels were generating about $400 in free power that we used in our home, and then $400/year in surplus (~10,000 kWh at 8.75 cents/kWh).
After the Leaf, our panels should generate the same $370 in free power that we use at home, $230 in power for the Leaf, and then about $160/year in surplus energy (2128 kWh at 7.41 cents/kWh), in part because our power rates went down.

Separate from these cost savings are the $5,000/year production incentive, which we get for generating at least 9260 kWh gross power, before household usage, at 54 cents/kWh. 

Also separate is the cost of gasoline we're not burning by driving the Leaf.  At $2/gallon the SUV costs us 11.7 cents/mile in gas (as compared to 1.9 cents/mile for the Leaf).  So driving 1000 miles/mo in the Leaf instead of the SUV would save us $98/mo in net fuel cost after accounting for electricity costs.  So that's ~$1400 in avoided gasoline costs and $230 in new power costs, for a net savings of $1170/year.  So from a financial perspective, our electricity is much more efficiently spent driving our car (if it displaces gasoline) than being sold back to the grid.

If I've done the math right, our household budget should be improved by $5k+$1170+$370+$160 = $7000 per year by having solar panels and an electric car.  That's $7k more I can put into the stock market.  Our total out of pocket costs for these items was about $30,000 (32k solar panels - 30% tax rebate +$7700 car), so one convoluted way to look at this math is that we're "earning" $7000 on $30k, or 23.3% guaranteed return per year.  That only lasts until 2020, at which point the production incentives expire, and our return drops to a more meager $2000/$30k or 6.66% per year.  Good for the environment AND my bottom line!

That math is more than a little bogus because it's figured on initial purchase price, not compound growth, because those profits are not re-invested into more income-producing assets like they would be if they were stock earnings.  I'm not complaining.
« Last Edit: March 10, 2016, 08:37:42 PM by sol »

nereo

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Re: solar panel installation
« Reply #156 on: March 10, 2016, 05:02:16 AM »
awesome update Sol.  I was actually wondering a few weeks ago how your power generation might have changed during this latest el nino and the rain it has brought.  Do you know how much power your panels collected in Jan/Feb 2015 vs 2014?

Quote
Also separate is the cost of gasoline we're not burning by driving the Leaf.  At $2/gallon the SUV costs us 11.7 cents/mile in gas (as compared to 1.9 cents/mile for the Leaf).  So driving 1000 miles/mo in the Leaf instead of the SUV would save us $98/mo in net fuel cost after accounting for electricity costs.  So that's ~$1400 in avoided gasoline costs and $230 in new power costs, for a net savings of $1170/year. So from a financial perspective, our electricity is much more efficiently spent driving our car (if it displaces gasoline) than being sold back to the grid.

sounds like you've found a good way to diversify yourself from being dependent on selling power back to the utility.  There's on guarantee that your utility will continue to buy back excess power in the future, right?
Now I'm curious about your experiences with the Leaf.  I'm guessing you also looked at the Volt and decided for the Leaf for some reason. 

An EV isn't in the cards for us just yet due to our onstreet parking situation (no way to plug it in as of right now). 

brooklynguy

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Re: solar panel installation
« Reply #157 on: March 10, 2016, 07:16:06 AM »
Thanks for the update.  You keep us energy-usage voyeurs happy.

That math is more than a little bogus because it's figured on initial purchase price, not compound growth, because those profits are not re-invested into more income-producing assets like they would be if they were stock earnings.

I think the math is actually bogus for a different reason.  You can reinvest your returns (the electricity/gasoline cost savings) however you please, including in productive assets like stocks.  But that math ignores the fact that you will never recoup any of your initial purchase price (assuming the solar panel system and LEAF will both eventually depreciate to zero).  But even factoring that in, it looks like you are getting a pretty solid return on your investment.

MasterStache

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Re: solar panel installation
« Reply #158 on: March 10, 2016, 08:56:03 AM »
Great update, wish I would have found this thread sooner. I'll read through it more in depth when I have some time. I understand you paid a company to install the panels? I wonder what sort of cost savings you could have created by installing yourself.

I installed 28 panels (I briefly spoke about this on your Leaf thread) in 2012 for total system cost of just under 15K, minus federal rebates. My panels were only 205 watts/per panel also. And I actually purchased them in 2011. I received a couple quotes of around 30K for a comparable system, so I figure I saved around half of the total cost by simply doing it myself. We sold the house in December 2014 and the solar array and subsequent energy savings were a huge selling feature. 

Axecleaver

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Re: solar panel installation
« Reply #159 on: March 10, 2016, 10:46:20 AM »
Great update, I'm jealous of your production incentive.

The way I'd look at the return is to consider the ROI. You've put in capital expenditures of ~$30k net after tax rebate. You generated $6275 in return last year: 400 in free power, 875 in excess power sold back to the grid, 5k in production incentives.  In future years you'll generate 7k a year. This probably accelerates as energy prices increase. So on a balance sheet:

Year Cost/      ROI
        Benefit
0     -32000   -32000 capex solar panels
0        9600    -22400 30% tax rebate 
1        6275    -16125 first year returns on power
2       -7700    -23825 capex leaf
2        7000    -16825  Year 2 returns on power
3        7500      -9325  Year 3 returns on power
4        8000      -1325  Year 4 returns on power
4        8500      7175   Year 5 returns on power; Break even point reached

So, if you hadn't bought the car, you would have achieved break even on your solar panels in year 3. The car capex slowed down your break even, but only by another year. The real value here is achieving energy independence and insulation from future energy shocks. That's a valuable risk mitigation achievement that shouldn't be overlooked. And, free solar panels after 3-4 years. Pretty awesome.

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Re: solar panel installation
« Reply #160 on: March 10, 2016, 11:27:22 AM »
Great update, I'm jealous of your production incentive.

The way I'd look at the return is to consider the ROI. You've put in capital expenditures of ~$30k net after tax rebate. You generated $6275 in return last year: 400 in free power, 875 in excess power sold back to the grid, 5k in production incentives.  In future years you'll generate 7k a year. This probably accelerates as energy prices increase. So on a balance sheet:

Year Cost/      ROI
        Benefit
0     -32000   -32000 capex solar panels
0        9600    -22400 30% tax rebate 
1        6275    -16125 first year returns on power
2       -7700    -23825 capex leaf
2        7000    -16825  Year 2 returns on power
3        7500      -9325  Year 3 returns on power
4        8000      -1325  Year 4 returns on power
4        8500      7175   Year 5 returns on power; Break even point reached

So, if you hadn't bought the car, you would have achieved break even on your solar panels in year 3. The car capex slowed down your break even, but only by another year. The real value here is achieving energy independence and insulation from future energy shocks. That's a valuable risk mitigation achievement that shouldn't be overlooked. And, free solar panels after 3-4 years. Pretty awesome.
You forget the depreciated value of the car. The balance sheet should show the cars value every year, it drastically improves the outcome.

I would show it as year 2-1$500 for the car, year 3 -$1200 etc. basically the cars depreciation (I don't really know the numbers, just guessing). He didn't lose $7700 all at once, he has the option to change his mind at any time and get some money back. 

Solar panels are harder to get money back from due to the removal/installation cost. When I looked at installing the installation was the same as the system, If I were to buy his used I couldn't offer much due to the labour costs for removal/install. That's why they aren't worth much after year 1, almost 100% depreciation unless sold with the house.

ulrichw

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Re: solar panel installation
« Reply #161 on: March 10, 2016, 05:41:52 PM »
I'm guessing with ~5000kWh of usage per year that your heat is probably natural gas.

The other thing you may want to look into (given probably temperate winters in your area) is installing heat pumps for heating (specifically ductless mini-splits, which are the most efficient). Depending on your heating load.

I'm considering doing exactly that (we just installed solar and also recently leased a VW E-Golf). In our case, I'm hoping to use the mini-splits as the main source of heating, while keeping the gas furnace for those times when we need a lot of heat quickly.

sol

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Re: solar panel installation
« Reply #162 on: March 10, 2016, 09:02:50 PM »
Do you know how much power your panels collected in Jan/Feb 2015 vs 2014?

Not exactly, no.  I know how much net surplus they generated above my household usage, but the only way to know the total PV generation is to manually read the direct power meter each month, or plug a laptop into my inverters.   Neither of which I have bothered to do.  It might be a fun weekend project at some point to download all of the inverter data, though.

Quote
There's on guarantee that your utility will continue to buy back excess power in the future, right?

No, and they've already started screwing with solar people by lowering the retail cost of electricity (thus lowering the rate they pay me for my surplus) and making up for it by increasing the monthly connection fee by 100%.   Most users saw no change in their bill.  Solar PV household saw their refund checks shrink by about 15% overnight.

Quote
Now I'm curious about your experiences with the Leaf.  I'm guessing you also looked at the Volt and decided for the Leaf for some reason. 

The Volt, like the Prius, still sends money to terrorists.  It still burns gasoline.  I wanted a pure EV with no tailpipe emissions at all, no blood money for ISIS, no cancer-causing fumes while refueling, lower operating and maintenance costs, no noise pollution, and 100% fueled by the solar panels on my roof.  Fortunately, my driving profile made a pure EV a good fit for my family.  I don't do long commutes, for reasons related to my hatred of traffic and waste.

If you're still interested in the Leaf, I wrote a whole post about it.  Hybrids are still gasoline cars, which are dirty and expensive and complicated machines, and then they ALSO have an EV system on top of that.  Pure EVs are simple, by comparison.

that math ignores the fact that you will never recoup any of your initial purchase price

Yes, and we discussed this point earlier in this very thread.  The solar panels have some residual value, but it's probably less than half of what I paid to have them installed.  It complicates the ROI calculation because you can depreciate them many different ways.

I understand you paid a company to install the panels? I wonder what sort of cost savings you could have created by installing yourself.

I paid for installation.  When I was shopping in 2014, residential solar panel installations were about 50% materials and 50% labor/design/permitting.  You need a licensed electrician to install the power meters and required safety devices.  And the material cost can vary widely, depending on where you're getting your panels and inverters from.  In my case, I paid a premium for the (locally manufactured) hardware in order to qualify for the (much higher) in-state production incentive of 54 cents/kWh produced on the roof.

I'm guessing with ~5000kWh of usage per year that your heat is probably natural gas.

The other thing you may want to look into (given probably temperate winters in your area) is installing heat pumps for heating (specifically ductless mini-splits, which are the most efficient).

Yes, our current furnace is natural gas (though the blower is of course electric).  It's also 18 years old and original to the house, so when it dies we'll probably install a traditional heat pump system in the same spot, since our house is already ducted.

« Last Edit: March 10, 2016, 10:18:43 PM by sol »

Mrs. PoP

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Re: solar panel installation
« Reply #163 on: March 11, 2016, 05:53:17 PM »
Do you know how much power your panels collected in Jan/Feb 2015 vs 2014?

Not exactly, no.  I know how much net surplus they generated above my household usage, but the only way to know the total PV generation is to manually read the direct power meter each month, or plug a laptop into my inverters.   Neither of which I have bothered to do.  It might be a fun weekend project at some point to download all of the inverter data, though.

Do you know what brand of inverters you have, Sol?   Ours are Enphase and communicate the panel production to A small box that feeds that information to our Enphase account.  Then I just open my Enphase app and it tells me exactly how many kWh we produced each hour.  To figure out how much we use on a monthly basis I just have to subtract the net surplus we sent to the grid for that same period.  I've been keeping track pretty closely in our first year to make sure production/usage is where we expected it to be.

Not gonna lie though, I love checking the app on a sunny day and seeing my solar panels cranking out the kWh. 


monarda

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Re: solar panel installation
« Reply #164 on: March 11, 2016, 07:01:20 PM »
Do you know how much power your panels collected in Jan/Feb 2015 vs 2014?

Not exactly, no.  I know how much net surplus they generated above my household usage, but the only way to know the total PV generation is to manually read the direct power meter each month, or plug a laptop into my inverters.   Neither of which I have bothered to do.  It might be a fun weekend project at some point to download all of the inverter data, though.

Do you know what brand of inverters you have, Sol?   Ours are Enphase and communicate the panel production to A small box that feeds that information to our Enphase account.  Then I just open my Enphase app and it tells me exactly how many kWh we produced each hour.  To figure out how much we use on a monthly basis I just have to subtract the net surplus we sent to the grid for that same period.  I've been keeping track pretty closely in our first year to make sure production/usage is where we expected it to be.

Not gonna lie though, I love checking the app on a sunny day and seeing my solar panels cranking out the kWh. 



Mrs.PoP, it sounds like you have microinverters? That's what we have. The Enphase Enlighten is a nice app- we use it too.  But I'm not sure that it works with the regular inverters

Mrs. PoP

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Re: solar panel installation
« Reply #165 on: March 12, 2016, 03:51:06 AM »
Do you know how much power your panels collected in Jan/Feb 2015 vs 2014?

Not exactly, no.  I know how much net surplus they generated above my household usage, but the only way to know the total PV generation is to manually read the direct power meter each month, or plug a laptop into my inverters.   Neither of which I have bothered to do.  It might be a fun weekend project at some point to download all of the inverter data, though.

Do you know what brand of inverters you have, Sol?   Ours are Enphase and communicate the panel production to A small box that feeds that information to our Enphase account.  Then I just open my Enphase app and it tells me exactly how many kWh we produced each hour.  To figure out how much we use on a monthly basis I just have to subtract the net surplus we sent to the grid for that same period.  I've been keeping track pretty closely in our first year to make sure production/usage is where we expected it to be.

Not gonna lie though, I love checking the app on a sunny day and seeing my solar panels cranking out the kWh. 



Mrs.PoP, it sounds like you have microinverters? That's what we have. The Enphase Enlighten is a nice app- we use it too.  But I'm not sure that it works with the regular inverters

Ahh, you're probably right that they are micro inverters.  I just always forget the micro part.  =)

MasterStache

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Re: solar panel installation
« Reply #166 on: March 14, 2016, 06:51:30 AM »
I understand you paid a company to install the panels? I wonder what sort of cost savings you could have created by installing yourself.

I paid for installation.  When I was shopping in 2014, residential solar panel installations were about 50% materials and 50% labor/design/permitting.  You need a licensed electrician to install the power meters and required safety devices.  And the material cost can vary widely, depending on where you're getting your panels and inverters from.  In my case, I paid a premium for the (locally manufactured) hardware in order to qualify for the (much higher) in-state production incentive of 54 cents/kWh produced on the roof.

Hmm, I suppose the requirements vary by state. A licensed electrician wasn't required for me. I did have to get a local zoning permit, a building permit, and have it inspected by an electrical inspector. My county required a licensed structural engineer to examine my roof structure. That was a bit of a ridiculous cost. We didn't have any local or state incentives, sadly. Just the federal rebate. We did sell quite a few SREC's though.  I think the 50/50 labor/material cost seems about average for most installations. 

Also our utility provider swapped our meter for free. Took maybe a 1/2 hour or so.
« Last Edit: March 14, 2016, 11:25:03 AM by BeginnerStache »

nawhite

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Re: solar panel installation
« Reply #167 on: March 14, 2016, 04:52:12 PM »
Either I'm reading this wrong or the math is wrong:
We just bought a Nissan Leaf all-electric car.  If it drives 1000 miles/month at 3.9 kWh/mile, it will use 256 kWh of electricity at a cost of 7.41 cents per kWh.  That works out to 1.9 cents per mile, or $19/mo.  In a year of driving, the Leaf should use about 3000 kWh and cost us $230 in electricity.

Shouldn't that come out to 3900kWh/month? Where does the 256kWh come from? That would make it 28.9 cents per mile or $289/month, $3468/year.

Unrelated, my panels just had their first birthday so here's my annual recap:

3.125 kW system cost $7672 after tax rebate (http://forum.mrmoneymustache.com/welcome-to-the-forum/solar-panel-installation/msg838113/#msg838113)
Generated: ~3400 kWh
Additional used from grid: ~800 kWh
Total used: ~4200 kWh

Cost per kWh from utility: $0.13
Subsidy per generated kWh: $0.03

So total cost without panels would have been $546 for the year. With the panels, I paid the utility $104, and got back $102 in subsidies. So in total I saved $544. $544/$7672 = 7.09% return. (-2.99% for the loan we used to buy them so really only 4.1% return).

Not great, not terrible. Before our loan, it's right around the S&P500 inflation adjusted CAGR. It will probably remain right around that or trend slightly down as the panels get dirty and degrade a little. Usually utility rates go up over time which is where you make your real money, but here they just announced they are going to re-jigger the tiered rates so those who use the least get a discount and those who use the most have bills that go up which is good. But we were already among the lowest users so our bill would have gone down even without the panels (probably to around $0.11/kWh). Oh well. We get to feel fuzzy inside.


sol

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Re: solar panel installation
« Reply #168 on: March 14, 2016, 07:01:35 PM »
Either I'm reading this wrong or the math is wrong:
We just bought a Nissan Leaf all-electric car.  If it drives 1000 miles/month at 3.9 kWh/mile, it will use 256 kWh of electricity at a cost of 7.41 cents per kWh.  That works out to 1.9 cents per mile, or $19/mo.  In a year of driving, the Leaf should use about 3000 kWh and cost us $230 in electricity.

Shouldn't that come out to 3900kWh/month? Where does the 256kWh come from? That would make it 28.9 cents per mile or $289/month, $3468/year.

I typo'd the units.  The Leaf gets 3.9 miles per kWh, not kWh/mile.  So 1000 miles/mo divided by 3.9 miles/kWh is 256 kWh/month.

« Last Edit: March 15, 2016, 10:34:34 AM by sol »

monarda

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Re: solar panel installation
« Reply #169 on: August 01, 2016, 09:51:22 PM »
Reviving this thread to see what you all think about this deal available to expand my system.
We've intended to (-some day-) expand our system, just wondering if now's the time.

How does $3.46 per watt sound for adding on 2.32 kW onto my system with microinverters?
That's before incentives.

That'll give us 4.24 kW total.

sol

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Re: solar panel installation
« Reply #170 on: April 05, 2017, 08:10:36 PM »
Every spring I find renewed personal interest in my solar panels, as they start ramping up production with the return of sunny weather.  Our panels (and thus this thread) are now almost three years old.

Net financial return thus far:  We paid $32,400 out of pocket in 2014 and then received $9720 in tax rebates and $4965 in production incentives the first year, and the maximum $5k production incentives in the second year, for a total cash payback thus far of $19,685.  It's hard to estimate the value of the free power we've been getting, but I'm ballparking it at $750/year (10,000 kWh at ~7.5 cents each).  All together, that's about 65% payback on our initial outlay, after 2.5 years.  By the time this August's incentive payment for 2016/17 arrives, that should rise to 83%.  By 2020 (when the system will be six years old) it should be ~130% payback, not counting residual value of the system or any future free power we get after that.

One of the amazing things to me is how much the prices of solar panels has come down, since we installed ours.  Residential solar panels appear to be dropping by about 10% per year, a rate that I would have thought was unsustainable three years ago when prices had already dropped so dramatically.  China is cranking out panels at a rate that will significantly alter the global energy industry within our lifetimes.  My system has only been more profitable than waiting out the price declines because we've been getting annual production incentives that (more than) offset the falling prices of new systems. 

There have been some hiccups along the way.  Last year my local utility company changed their fee structure, increasing the monthly connection fee from $5/mo to $10/mo while lowering the per kWh cost of power, which together cost me about $100/year.  And now they're talking about raising the connection fee to $16/mo over the next two years, but also raising the retail rate by a few percent, so those changes together will cost me about another $50/year.  Now that we're about energy neutral on an annual basis, the per kWh cost of power is basically irrelevant to us on a net basis, and we mostly worry about the monthly connection fee.  They are working hard to screw over residential solar power owners around here, which angers me because solar homeowners fronted the capital to provide my utility with capacity increases for which the utility gets federal subsidies, and now they are changing the rules under which we all made that decision.

One additional hiccup we've had is that one of our two inverters went offline in the middle of the dark months, and we didn't notice for about a month until our next power bill came in.  We lost about 400 kWh of production, which would normally have cost us about $200 in production incentives in our next check.  Fortunately, our system is a little oversized for the subsidy and we normally generate more than the maximum $5000 incentive, so I don't think it will actually hurt us as long as they stay functional through the summer months.

Attached Graph is net power consumption as measured by the power company.  It's a positive number in the winter, when we pay for power, and a negative number in the summer, when they pay us for power.  The seasonal sin wave is offset upwards in early 2016 when we bought the electric car, and will be unusually high for the billing periods covering our recent inverter failure.

 

Ben Hogan

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Re: solar panel installation
« Reply #171 on: April 06, 2017, 06:26:21 AM »
Sol, what city do you live in and who is your power company. Also can you post some pictures of the charge controller and connections?

Thanks.

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Re: solar panel installation
« Reply #172 on: April 06, 2017, 11:22:15 AM »
Our experience and setup is very similar to Sol's after two years of having the panels installed.

Has anyone installed or considered installing a battery like Tesla's Powerwall to store power for off-grid and non-peak sunlight days?

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Re: solar panel installation
« Reply #173 on: April 18, 2017, 02:33:00 PM »

One of the amazing things to me is how much the prices of solar panels has come down, since we installed ours.  Residential solar panels appear to be dropping by about 10% per year, a rate that I would have thought was unsustainable three years ago when prices had already dropped so dramatically.  China is cranking out panels at a rate that will significantly alter the global energy industry within our lifetimes.  My system has only been more profitable than waiting out the price declines because we've been getting annual production incentives that (more than) offset the falling prices of new systems. 


Sol - I'm curious if there would ever be a point when you'd swap out your panels for ones that are more efficient... maybe not today but perhaps in the future should efficiency and cost trends continue.  I'm thinking less about maximizing output during sunny summer days and more about 'raising the floor' during the shorter, rainy winter months.  guessing it would have to involve a complete change in your excess-production incentives.


sol

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Re: solar panel installation
« Reply #174 on: April 18, 2017, 03:13:54 PM »
Also can you post some pictures of the charge controller and connections?

Inside my garage there are two wall mounted inverters (left), next to a solar breaker box (middle) next to my regular circuit breaker box (right, inset in wall).  There is also an extra power meter for measuring total solar production, which is installed outside next to my regular net power meter.  The solar meter is currently counting upwards, because we're generating power.  The net power meter is currently spinning backwards because the sun is out and we're feeding power back into the grid.

One side effect of this arrangement is that we still have an incentive to conserve electricity, because we "pay" for every kWh we use.  On an annual basis we generate more than we use, and the power company pays us the retail power rate for our surplus (by applying it against our connection fees and water bill, since they are integrated).  So even though we don't use all the power we generate, if we were to leave more lightbulbs burning around here we would end up getting paid less for the surplus.

sol

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Re: solar panel installation
« Reply #175 on: April 18, 2017, 03:26:58 PM »
Sol - I'm curious if there would ever be a point when you'd swap out your panels for ones that are more efficient...

I would consider adding new panels to the system if I had a good place to put them, like an outbuilding or pagoda or something, but I don't think it makes sense to increase the efficiency of my current system at today's prices, or near-future prices.  Most of the payback I'm getting is from the state-sponsored 54 cents//kWh production incentive (which pays me $5k/year) and not from the free power we get (which pays me about $800/year).  When the state production incentive expires in 2020 and we're back to straigh retail power rates of ~8 cents/kWh, even doubling the efficiency of the panels would only make me another $800/year.  For an equivalent five year payback expectation, those double-efficient panels would have to drop to $4k installed.  That's 27 cents/kW installed, which is pretty far below any projections I've seen anywhere for the future cost of residential solar.

Fortunately, solar panels have long useful lifetimes even at severely degraded efficiencies, so old ones are likely to stay around a while.  There is always more available roof space for new panels, so I don't expect anyone to start upgrading their panel efficiencies until every valid roof in the country is covered.

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Re: solar panel installation
« Reply #176 on: June 14, 2017, 12:14:59 PM »
Thank you Sol and other contributors to this thread, I've learned so much! We are looking into solar for a South Florida home. Due to state energy lobbyists FL does not offer rebates/benefits so payback may shift quite a bit to the right. :(

Any South Fla folks on the thread willing to discuss their experience? Bonus points if in the Keys :)

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Re: solar panel installation
« Reply #177 on: June 14, 2017, 02:07:14 PM »
Sol - I'm curious if there would ever be a point when you'd swap out your panels for ones that are more efficient... maybe not today but perhaps in the future should efficiency and cost trends continue.  I'm thinking less about maximizing output during sunny summer days and more about 'raising the floor' during the shorter, rainy winter months.  guessing it would have to involve a complete change in your excess-production incentives.

No point in removing old panels unless you are totally out of roof space. Waste of time and effort. If you need more panels due to age/loss of output - just add another panel or two to the existing system.

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Re: solar panel installation
« Reply #178 on: June 14, 2017, 05:43:21 PM »
Thank you Sol and other contributors to this thread, I've learned so much! We are looking into solar for a South Florida home. Due to state energy lobbyists FL does not offer rebates/benefits so payback may shift quite a bit to the right. :(

Any South Fla folks on the thread willing to discuss their experience? Bonus points if in the Keys :)

We're s fl, but not Monroe county and got our installation a littl more than 2 years ago.   Ping me by pm if you wants details of our setup and costs, etc.  =)

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Re: solar panel installation
« Reply #179 on: June 14, 2017, 06:47:19 PM »
Sol - I'm curious if there would ever be a point when you'd swap out your panels for ones that are more efficient... maybe not today but perhaps in the future should efficiency and cost trends continue.  I'm thinking less about maximizing output during sunny summer days and more about 'raising the floor' during the shorter, rainy winter months.  guessing it would have to involve a complete change in your excess-production incentives.

No point in removing old panels unless you are totally out of roof space. Waste of time and effort. If you need more panels due to age/loss of output - just add another panel or two to the existing system.
Sol already answered, but I asked in part because it didn't seem like there was room on his roof to simply add more panels (look back alllllll the way on page 1)

sol

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Re: solar panel installation
« Reply #180 on: June 14, 2017, 11:40:25 PM »
Sol - I'm curious if there would ever be a point when you'd swap out your panels for ones that are more efficient... maybe not today but perhaps in the future should efficiency and cost trends continue.  I'm thinking less about maximizing output during sunny summer days and more about 'raising the floor' during the shorter, rainy winter months.  guessing it would have to involve a complete change in your excess-production incentives.

No point in removing old panels unless you are totally out of roof space. Waste of time and effort. If you need more panels due to age/loss of output - just add another panel or two to the existing system.

Sol already answered, but I asked in part because it didn't seem like there was room on his roof to simply add more panels (look back alllllll the way on page 1)

Nereo is right that I don't really have more room, with panels of these dimensions.

Personally, I'm not worried about "raising the floor" in the winter months because I'm grid-tied, and our power here is mostly hydropower anyway.  Remember that every part of the planet gets the same amount of sunlight on an annual basis, the poles just get six months of light and six months of dark.  It all averages out, though, so your latitude doesn't really matter much in terms of total watts received per year and if you're grid tied the winter deficiency isn't a problem.

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Re: solar panel installation
« Reply #181 on: June 15, 2017, 11:02:26 AM »
Sol - I'm curious if there would ever be a point when you'd swap out your panels for ones that are more efficient... maybe not today but perhaps in the future should efficiency and cost trends continue.  I'm thinking less about maximizing output during sunny summer days and more about 'raising the floor' during the shorter, rainy winter months.  guessing it would have to involve a complete change in your excess-production incentives.

No point in removing old panels unless you are totally out of roof space. Waste of time and effort. If you need more panels due to age/loss of output - just add another panel or two to the existing system.

Sol already answered, but I asked in part because it didn't seem like there was room on his roof to simply add more panels (look back alllllll the way on page 1)

Nereo is right that I don't really have more room, with panels of these dimensions.

Personally, I'm not worried about "raising the floor" in the winter months because I'm grid-tied, and our power here is mostly hydropower anyway.  Remember that every part of the planet gets the same amount of sunlight on an annual basis, the poles just get six months of light and six months of dark.  It all averages out, though, so your latitude doesn't really matter much in terms of total watts received per year and if you're grid tied the winter deficiency isn't a problem.
There is a caveat there, not every part of the earths surface receives equal sunlight (you can define planet as upper atmosphere or ground). If you live in a sunny part of Canada you can get more sunlight than Seattle for example. In North America the longitude makes more difference than latitude ;)

As a tangent, the newer versions of Climate change model predict increased cloud cover, which decreases solar potential for much of NA. Going forward to 2050 the effect may be larger in magnitude for parts of North America than the efficiency decline in solar panels (I'll need to research regional variations). While efficiency declines are real, the other part is the variation in solar hitting panels. 2050 is relevant as Sol is likely to still have the panels on his roof in 30 years.
https://www.nsf.gov/news/special_reports/clouds/question.jsp           laymans article

sol

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Re: solar panel installation
« Reply #182 on: June 15, 2017, 11:31:08 AM »
There is a caveat there, not every part of the earths surface receives equal sunlight (you can define planet as upper atmosphere or ground). If you live in a sunny part of Canada you can get more sunlight than Seattle for example.

PS is exactly right.  The problem with solar panels in my area isn't the latitude, it's the ~60% of days that are cloudy due to proximity to the ocean.  Those clouds reflect away lots of sunlight that could be powering my home.

On the bright side, locally made panels can be manufactured for optimal conversion efficiency under lower diffuse lighting conditions, rather than blazing sun.  My panels still generate more power annually than my household uses, even in grey rain land.  It's about 10,000 kWh per year, from 7560W of panels (28 panels at 270W each).

MVal

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Re: solar panel installation
« Reply #183 on: July 18, 2017, 01:32:30 PM »
Does anyone know anything about community solar farms? My local utility company has announced that coming soon will be opportunity to "lease" a solar panel at a local solar farm in exchange for a reduced electrical rate. Has anyone done this with their local utility company?

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Re: solar panel installation
« Reply #184 on: July 20, 2017, 12:20:34 PM »
It's a way for them to capture the tax incentives and pass through a portion of it to the rate consumer. For example, a non-profit typically can't benefit from tax incentives on solar because they don't pay taxes. But a for-profit community solar farm can, and then a non-profit (or you) can lease a piece of that and enjoy the benefits.

Run the numbers and if it works, do it!

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Re: solar panel installation
« Reply #185 on: July 20, 2017, 02:41:15 PM »
Sol - I'm curious if there would ever be a point when you'd swap out your panels for ones that are more efficient... maybe not today but perhaps in the future should efficiency and cost trends continue.  I'm thinking less about maximizing output during sunny summer days and more about 'raising the floor' during the shorter, rainy winter months.  guessing it would have to involve a complete change in your excess-production incentives.

No point in removing old panels unless you are totally out of roof space. Waste of time and effort. If you need more panels due to age/loss of output - just add another panel or two to the existing system.

Sol already answered, but I asked in part because it didn't seem like there was room on his roof to simply add more panels (look back alllllll the way on page 1)

Nereo is right that I don't really have more room, with panels of these dimensions.

Personally, I'm not worried about "raising the floor" in the winter months because I'm grid-tied, and our power here is mostly hydropower anyway.  Remember that every part of the planet gets the same amount of sunlight on an annual basis, the poles just get six months of light and six months of dark.  It all averages out, though, so your latitude doesn't really matter much in terms of total watts received per year and if you're grid tied the winter deficiency isn't a problem.

I don't think that's true.  You get the same amount of daylight, but not actual photons.  The closer you are to the equator the more direct the sun rays are, and you get more photons per unit of area. 

nereo

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Re: solar panel installation
« Reply #186 on: July 20, 2017, 02:56:57 PM »
Sol - I'm curious if there would ever be a point when you'd swap out your panels for ones that are more efficient... maybe not today but perhaps in the future should efficiency and cost trends continue.  I'm thinking less about maximizing output during sunny summer days and more about 'raising the floor' during the shorter, rainy winter months.  guessing it would have to involve a complete change in your excess-production incentives.

No point in removing old panels unless you are totally out of roof space. Waste of time and effort. If you need more panels due to age/loss of output - just add another panel or two to the existing system.

Sol already answered, but I asked in part because it didn't seem like there was room on his roof to simply add more panels (look back alllllll the way on page 1)

Nereo is right that I don't really have more room, with panels of these dimensions.

Personally, I'm not worried about "raising the floor" in the winter months because I'm grid-tied, and our power here is mostly hydropower anyway.  Remember that every part of the planet gets the same amount of sunlight on an annual basis, the poles just get six months of light and six months of dark.  It all averages out, though, so your latitude doesn't really matter much in terms of total watts received per year and if you're grid tied the winter deficiency isn't a problem.

I don't think that's true.  You get the same amount of daylight, but not actual photons.  The closer you are to the equator the more direct the sun rays are, and you get more photons per unit of area.

You are right in that total irradience is not the same in all locations, and is influenced by the angle of the sun (and cloud cover).  I'm left wondering what practical effect this has, though.  As I understand it output does not scale linearly with irradience.  In other words, the power output when it is 3000 E/m2 (typical of mid-day in the tropics) is not 50% more than when it is 'just' 2000E/m2 (values more typical of a sunny day in New England).

Where will you get better power output/day - somewhere where there's 18 hours of daylight but where the sun is at a steeper angle, or near the equator where you get a 12 hours, and several hours the sun is beating directly down on the panel.

Given the number of PV panels throughout Germany (latitude often >45) its still clearly 'worth it' in many locales. 

sol

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Re: solar panel installation
« Reply #187 on: July 20, 2017, 03:04:41 PM »
Sol - I'm curious if there would ever be a point when you'd swap out your panels for ones that are more efficient... maybe not today but perhaps in the future should efficiency and cost trends continue.  I'm thinking less about maximizing output during sunny summer days and more about 'raising the floor' during the shorter, rainy winter months.  guessing it would have to involve a complete change in your excess-production incentives.

No point in removing old panels unless you are totally out of roof space. Waste of time and effort. If you need more panels due to age/loss of output - just add another panel or two to the existing system.

Sol already answered, but I asked in part because it didn't seem like there was room on his roof to simply add more panels (look back alllllll the way on page 1)

Nereo is right that I don't really have more room, with panels of these dimensions.

Personally, I'm not worried about "raising the floor" in the winter months because I'm grid-tied, and our power here is mostly hydropower anyway.  Remember that every part of the planet gets the same amount of sunlight on an annual basis, the poles just get six months of light and six months of dark.  It all averages out, though, so your latitude doesn't really matter much in terms of total watts received per year and if you're grid tied the winter deficiency isn't a problem.

I don't think that's true.  You get the same amount of daylight, but not actual photons.  The closer you are to the equator the more direct the sun rays are, and you get more photons per unit of area.

I think this a geometry miscommunication.  The poles receive less energy per unit surface area of the planet, but not per unit surface area of the panels because the panels are tilted.  The area is different by the cos of the panel height.

There are other factors, of course. The poles are technically one earth radius farther away from the sun than the equator, so they receive very slightly less light by the inverse square law for distance.  And the ray path intersects more atmosphere at the poles because it comes in at a lower angle, so you get more scattering and absorption.  And the arc in the sky is longer at the poles, so they only receive the same amount of light if both locations were to use sun tracking panels.

But these are all details, compared to the amount of cloud cover you get in any location. 

frugalnacho

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Re: solar panel installation
« Reply #188 on: July 20, 2017, 03:06:12 PM »
Sol - I'm curious if there would ever be a point when you'd swap out your panels for ones that are more efficient... maybe not today but perhaps in the future should efficiency and cost trends continue.  I'm thinking less about maximizing output during sunny summer days and more about 'raising the floor' during the shorter, rainy winter months.  guessing it would have to involve a complete change in your excess-production incentives.

No point in removing old panels unless you are totally out of roof space. Waste of time and effort. If you need more panels due to age/loss of output - just add another panel or two to the existing system.

Sol already answered, but I asked in part because it didn't seem like there was room on his roof to simply add more panels (look back alllllll the way on page 1)

Nereo is right that I don't really have more room, with panels of these dimensions.

Personally, I'm not worried about "raising the floor" in the winter months because I'm grid-tied, and our power here is mostly hydropower anyway.  Remember that every part of the planet gets the same amount of sunlight on an annual basis, the poles just get six months of light and six months of dark.  It all averages out, though, so your latitude doesn't really matter much in terms of total watts received per year and if you're grid tied the winter deficiency isn't a problem.

I don't think that's true.  You get the same amount of daylight, but not actual photons.  The closer you are to the equator the more direct the sun rays are, and you get more photons per unit of area.

You are right in that total irradience is not the same in all locations, and is influenced by the angle of the sun (and cloud cover).  I'm left wondering what practical effect this has, though.  As I understand it output does not scale linearly with irradience.  In other words, the power output when it is 3000 E/m2 (typical of mid-day in the tropics) is not 50% more than when it is 'just' 2000E/m2 (values more typical of a sunny day in New England).

Where will you get better power output/day - somewhere where there's 18 hours of daylight but where the sun is at a steeper angle, or near the equator where you get a 12 hours, and several hours the sun is beating directly down on the panel.

Given the number of PV panels throughout Germany (latitude often >45) its still clearly 'worth it' in many locales.

Well that place getting 18 hours of daylight will only be getting 6 hours of daylight in 6 months.   I would expect that the location at the equator would have not only more stable power through the year (12 hours every day all year), but it would produce more power because it's getting far more actual energy than the higher latitude. 

I'm not a solar panel expert, but I gotta imagine it has a very real effect on the power generated even if it's not a linear scale.  I'm not saying it's not worth it anywhere but the equator, just pointing out that what Sol said isn't technically true.

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Re: solar panel installation
« Reply #189 on: July 20, 2017, 03:19:55 PM »
I think this a geometry miscommunication.  The poles receive less energy per unit surface area of the planet, but not per unit surface area of the panels because the panels are tilted.  The area is different by the cos of the panel height.

There are other factors, of course. The poles are technically one earth radius farther away from the sun than the equator, so they receive very slightly less light by the inverse square law for distance.  And the ray path intersects more atmosphere at the poles because it comes in at a lower angle, so you get more scattering and absorption.  And the arc in the sky is longer at the poles, so they only receive the same amount of light if both locations were to use sun tracking panels.

But these are all details, compared to the amount of cloud cover you get in any location.

That will be true for any single panel in theory, but how do you arrange an entire array without running into practical limitations?  At my latitude there's about a 30% reduction in intensity vs the equator.  I'd have to have some pretty tall solar panels, and cast a large shadow on my neighbors house, in order to angle the entire square footage of my roof to match the intensity at the equator.   How could you even accomplish this at the poles? You'd just be building them sideways into space.

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Re: solar panel installation
« Reply #190 on: July 20, 2017, 03:27:47 PM »
just pointing out that what Sol said isn't technically true.

Should I have included a picture on my explanation above about who it is true?  You're thinking about surface area of the ground, not surface area of the panel.  The farther north you go the more the panel is tilted toward vertical to have the same amount of cross sectional area exposed to the sun.  Same exposed area, same instantaneous power output.

Even at the literal pole in an idealized case, the panel would be mounted perfectly vertically and would get the same amount of instantaneous energy while the ground was getting zero.  Just because the earth gets less energy at the poles does not mean the panel gets less.

I'd have to have some pretty tall solar panels, and cast a large shadow on my neighbors house, in order to angle the entire square footage of my roof to match the intensity at the equator.   How could you even accomplish this at the poles? You'd just be building them sideways into space.

Fortunately, residential panels are typically built flush with your roof, and more northern climates already have more steeply pitched roofs.

I agree that panel shading is a problem for utility scale solar fields at high northern latitudes.  Fortunately we don't build them at the poles anyway, and such large scale installations are never designed to have 100% coverage anyway, because you need access to all of the panels.  Tilting them makes this easier, arguable allowing for more panels per acre off the equator than on it.

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Re: solar panel installation
« Reply #191 on: July 20, 2017, 05:27:46 PM »
just pointing out that what Sol said isn't technically true.

Should I have included a picture on my explanation above about who it is true?  You're thinking about surface area of the ground, not surface area of the panel.  The farther north you go the more the panel is tilted toward vertical to have the same amount of cross sectional area exposed to the sun.  Same exposed area, same instantaneous power output.

Even at the literal pole in an idealized case, the panel would be mounted perfectly vertically and would get the same amount of instantaneous energy while the ground was getting zero.  Just because the earth gets less energy at the poles does not mean the panel gets less.

I'd have to have some pretty tall solar panels, and cast a large shadow on my neighbors house, in order to angle the entire square footage of my roof to match the intensity at the equator.   How could you even accomplish this at the poles? You'd just be building them sideways into space.

Fortunately, residential panels are typically built flush with your roof, and more northern climates already have more steeply pitched roofs.

I agree that panel shading is a problem for utility scale solar fields at high northern latitudes.  Fortunately we don't build them at the poles anyway, and such large scale installations are never designed to have 100% coverage anyway, because you need access to all of the panels.  Tilting them makes this easier, arguable allowing for more panels per acre off the equator than on it.

No I understand what you're saying, I typed that comment before your last post, even though it posted after you.

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Re: solar panel installation
« Reply #192 on: July 21, 2017, 01:16:26 AM »
just pointing out that what Sol said isn't technically true.

Should I have included a picture on my explanation above about who it is true?  You're thinking about surface area of the ground, not surface area of the panel.  The farther north you go the more the panel is tilted toward vertical to have the same amount of cross sectional area exposed to the sun.  Same exposed area, same instantaneous power output.

Even at the literal pole in an idealized case, the panel would be mounted perfectly vertically and would get the same amount of instantaneous energy while the ground was getting zero.  Just because the earth gets less energy at the poles does not mean the panel gets less.

I'd have to have some pretty tall solar panels, and cast a large shadow on my neighbors house, in order to angle the entire square footage of my roof to match the intensity at the equator.   How could you even accomplish this at the poles? You'd just be building them sideways into space.

Fortunately, residential panels are typically built flush with your roof, and more northern climates already have more steeply pitched roofs.

I agree that panel shading is a problem for utility scale solar fields at high northern latitudes.  Fortunately we don't build them at the poles anyway, and such large scale installations are never designed to have 100% coverage anyway, because you need access to all of the panels.  Tilting them makes this easier, arguable allowing for more panels per acre off the equator than on it.

Even better, at the pole you can just create a tower of panels 5 miles tall.  The effective irradiance per sq meter of land is enormous as long as you are willing to leave the ground!

frugalnacho

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Re: solar panel installation
« Reply #193 on: July 21, 2017, 08:15:31 AM »
Even better, at the pole you can just create a tower of panels 5 miles tall.  The effective irradiance per sq meter of land is enormous as long as you are willing to leave the ground!


MrSal

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Re: solar panel installation
« Reply #194 on: August 25, 2018, 10:44:17 AM »
Sorry to revive this thread but after reading a bit about solar I was trying to see if it made sense installing them.

Sol's selling price per kWh back to the grid is amazing btw.

I was trying to figure out the rebates and incentives available to someone that lives in PA?

From the reading i was able to do, 30% Federal Rebate is guaranteed... how about any other rebates? I think utilities buy the electricity generated at a 1 to 1 ratio, so in essence, there is no free lunch here unfortunately - unless I saw it wrong.

Is there someone in PA that underwent the process of installing solar panels?

nereo

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Re: solar panel installation
« Reply #195 on: August 25, 2018, 10:52:49 AM »
@sol - update! update! update!

TomTX

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Re: solar panel installation
« Reply #196 on: August 25, 2018, 12:49:44 PM »
Sorry to revive this thread but after reading a bit about solar I was trying to see if it made sense installing them.

Sol's selling price per kWh back to the grid is amazing btw.

I was trying to figure out the rebates and incentives available to someone that lives in PA?

From the reading i was able to do, 30% Federal Rebate is guaranteed... how about any other rebates? I think utilities buy the electricity generated at a 1 to 1 ratio, so in essence, there is no free lunch here unfortunately - unless I saw it wrong.

Is there someone in PA that underwent the process of installing solar panels?
Ask your power provider how it works with them.

Cadman

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Re: solar panel installation
« Reply #197 on: August 26, 2018, 01:29:54 PM »
Yes, absolutely talk with your power company first as protocol varies PoCo to PoCo. Some offer rebates, some don't. Some will bank your credits, and some put a 12 month limit on them. Some cut you a check for excess each month, others don't. That's step 1.

For those that are handy, just this week Renvu was advertising a complete 7.5kW roof mount system for $1.575/watt, with Unirac racking and Solaria panels with micro-inverters. Might be a good deal for someone.



sol

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Re: solar panel installation
« Reply #198 on: August 29, 2018, 04:03:08 PM »
@sol - update! update! update!

update!

I haven't been paid yet for this year, and I'm grumpy about it.  Washington state's solar incentive program went through some administrative changes this year, and while they are in theory honoring the same deal, payment is supposed to be delayed up to two months.  I expect to get paid in October for the production year ending in June.

But my system is still maxing out my $5k/year rebate, so I'm happy.  Recall that I have twenty-eight 270 Watt panels on my roof, for a total of 7560 Watts of capacity.  Those panels need to generate at least 9260 kWh per production year in order to max out my rebate check (because they pay $0.54/kWh produced), which means my panels would need to see the equivalent of 1200 hours of full sun over the course of the year.  That's only 3.5 hours of full sun per day!

In reality, I probably get less than that in the rainy winters, but far more in the blazing hot summers. 

A quick check of my inverters in the garage suggests my roof has generated approximately 43 MWh since being installed in 2014.  This is significantly more than my total household usage since then, including replacing auto gasoline with an electric car and replacing natural gas heating with an electric heat pump.  At the national average of 15 cents per kWh, that 43 MWh is worth about $6500 of free electricity, but in reality my local power costs less than that due to existing hydropower surpluses, so it's probably more like $3500 of power. 

On top of the $3500 of free power, I have already received three $5k incentive payment checks and a $9,700 tax rebate.  After this year's incentive check arrives in October, my system will have more than paid for itself in 4 years and 3 months.  Going forward, I expect two more $5k incentive checks until the rebate program expires in 2020, and of course I will continue to get ~$800 of free electricity every year for the life of the panels.  Calculating an accurate ROI on this system is basically impossible because the returns are time-delayed and very lumpy, but suffice it to say I would have done better financially by putting the entire up-front cost into the stock market in early 2014, because the market has been bananas.

Compared to today's costs for solar panels, I dramatically overpaid back in 2014 (over $4 per Watt installed).  Remember from the OP that I paid extra for locally-made panels and inverters in order to get the higher incentive payments.  For someone looking to do something of similar size today, I would expect to pay much less up front, and also get much less back each year.  My system is sort of a historical oddity, by now.

In the graph below, I can clearly see the impact of replacing a bunch of gasoline consumption with an electric car (in 2016) and then replacing a bunch of natural gas consumption with an electric heat pump (in 2017).  Both of those have increased our household electricity consumption (though lowered our total costs) and I don't think that our household will continue to be net-negative for electricity going forward.  It will be close, though, and we may dip back into net negative territory after my kids start moving out in a few years.
« Last Edit: August 29, 2018, 04:22:34 PM by sol »

Prairie Stash

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Re: solar panel installation
« Reply #199 on: August 29, 2018, 05:46:35 PM »
The ROI is hard. You put an undisclosed amount onto a 0% card for 9 months with a 1% cashback. You received 1/3 back in the first year - $5000+9720 ($14,720). Right now the growth on the outlay would be $16,000.

June 2014 S&P was 1947, today its 2914. If you reinvested each payment when you received it, how much would you get?
June 2015 to now, $14720, would have grown $5000.
June 2016 to now, $5000, growth $1800
June 2017 to now $5000 growth $800
October 2018 $5000
4 years power saving $3,200

I see at least $7600 in growth from reinvesting payments. Your system is paid for already (assuming reinvestments, but you're Sol so its a safe assumption).

When you get your check, you'll be $8000 behind leaving it in the market. But you get another 3 lumps of $5000 coming and residuals of $800/year for another 20 years.

I'm going out there saying you'll beat the market with this decision.

Reply#32
"My up front cost was 32,400.  That money is gone, so I'm $32,400 in the hole on day one.  Over the next six years I'll collect $30,000 in incentive payments, $9720 in tax rebate, and about $800/year in reduced power bills for a six year total of $44,520.

My $32,400 initial investment would have to grow at 6.56% per year to be worth $44,520 after six years, assuming annual compounding.

And my return should actually be a little better than that, because I'm getting about a third of that total ($9720+$5000+$800) back in the first year, not at the end"

Please check my math. Initially you pointed out that you should compare based on reinvestments, considering 1/3 was rebated upfront.