Solar Power Question/Thoughts Analysis

[FIRE47]

Has anyone considered net metering or going fully off grid as an investment or part of FIRE plans?

Without government subsidy the payback period appears prohibitive however with the new subsidies that are going to roll out where I live it appears to be an interesting option.

Where I live they will pay you $1k per KW to setup a grid tied in system, it would cost around $12-15k installed to offset all my useage. This would thus come out to a net cost for me of lets call it $8,500 to never pay for useage again. The problem is they will still hit you with fixed charges which really hurts the ROI.

Based on the costs in my area this works out to around 5.5-6.5% return or a simple payback period of around 15+ years - the fixed charges are killing the feasibility as they around 1/3 of my current bill. Personally I do not find this to be worth it although apparently such an installation would increase my property value by at least $12-15k or basically the cost of the system according to a few sources. Thoughts?

Now where the interesting part is that the same program will pay you triple the subsidy or $3k per KW to build a fully off the grid system, and thus I would also be able to eliminate any fixed charges as well - the cost for such a project is roughly 2 times the cost of a tied in system however due to the more generous subsidy I would only be out $12k or so and also be able to eliminate all fixed charges which would bring my return to about 9% while having a fully self contained system.

I would probably have to reconnect to the grid if I ever went to resell but the system could still be put back on the grid so presumabely would still add the same $12k or so to my property value assuming being off the grid is worthless or even a negative at best to most normal folk.

[one piece at a time]

I have recently installed a large roof top array on the north west of my (southern hemisphere) house. We went with a grid tied bare bones system. After 14 months I had a look at the total power produced and the purchase price and it seems the simple payback is between 3 and 5 years, depending on the fraction of the electricity that is "self consumed".

I don't consider this part of my FIRE planning, but actually installed it so that I could run the AC a little cooler in summer without feeling bad about it! This keeps my wife happy. Two unexpected bonuses are that the panels cool the house through shading and the AC no longer trips out on hot days when both compressors are running as there is better regulation of the voltage at the meter.

We live in an area that has commercial solar farms, so that was a strong indication to me that the numbers should stack up. To be honest I didn't spend a lot of time on the analysis as we installed the system before we had detailed information about our power use here.

[Syonyk]

Has anyone considered net metering or going fully off grid as an investment or part of FIRE plans?

Yes, to an extent.  However, it's not really FIRE so much as it is "aiming to provide a large portion of our needs locally," with added insulation from cost fluctuations down the road.  I'm not sure that it will save me money over remaining grid tied, but I care less about that than I do about having a useful system for long term stable power I can rely on.  I'm one hell of a pessimist about a lot of things, so take that into account.

Where I live they will pay you $1k per KW to setup a grid tied in system, it would cost around $12-15k installed to offset all my useage. This would thus come out to a net cost for me of lets call it $8,500 to never pay for useage again. The problem is they will still hit you with fixed charges which really hurts the ROI.

Where on earth do you live with that sort of absurdity?  Do you get the federal tax credit as well?

Now where the interesting part is that the same program will pay you triple the subsidy or $3k per KW to build a fully off the grid system, and thus I would also be able to eliminate any fixed charges as well - the cost for such a project is roughly 2 times the cost of a tied in system however due to the more generous subsidy I would only be out $12k or so and also be able to eliminate all fixed charges which would bring my return to about 9% while having a fully self contained system.

The trick here is that off grid power is among the most expensive power you can produce.  A small solar/battery/generator system will not beat out grid prices unless you're paying $0.50/kWh or something silly like that.  I'm not sure why they're trying to drive grid destruction as well, but that's how you write policies to do it...

Remember, in 10-15 years, you won't get that huge wad of cash when the batteries need replacement.  Or, if you don't take care of them, a lot sooner.  Off grid systems can kill a battery bank in a year, when the same system, well configured and properly run, can get 10 years out of the same set.

In relevant reading, I've written a few blog posts recently on the nature of offgrid power and solar you might want to read for some background.  I make my living in an off grid office because trenching in my area is quite difficult.

https://syonyk.blogspot.com/2018/05/why-typical-home-solar-setup-does-not-work-off-grid.html

https://syonyk.blogspot.com/2018/05/so-you-wanna-go-off-grid.html

https://syonyk.blogspot.com/2018/04/off-grid-system-design-considerations.html

And, if you're planning to use lead acid batteries, https://syonyk.blogspot.com/2018/04/off-grid-rv-lead-acid-maintenance-charging-failure-modes.html

I'm in the design stages of a system for our house, that I intend to install next year (last year of the 30% tax credit).  Because I've got a fairly small roof and comical setback requirements, I'm going with a ground mount system.  Either a horizontal axis tracker I'll build, or fixed panels in a "virtual tracking" setup with east/west facing strings, to optimize morning and evening production at the expense of mid-day production.  This is useful because I expect net metering is going away in my area, and I want to be better situated to deal with that.  I'm not sure what's replacing it, but net metering is a crap deal for utilities, and I certainly don't expect it to be present in 30 years in present form.  "I give you a kWh when convenient, and then I take a kWh when convenient, and you have no control over any of this" isn't something that makes a grid very stable.

My system design is going to be grid tied, but capable of indefinite off grid operation (at least until I run out of propane for the generator).  I'm planning to put an 8kW Outback Radian in for inverter duty, with "most of the house" as the critical loads panel.  This includes moving things like the heat pump compressor to that panel, and the well pump.  So a good hunk of pulling wire around, which isn't going to be fun, because those are high draw loads.  Alternately, I might just add another box outside.  Haven't decided yet.  But I want most of the house post-inverter.

The crawlspace will have a small-ish (~15-25kWh) battery bank, almost certainly lead acid of some variety, because it works well.  Vented properly, of course.  I can upgrade that if needed, but with a self starting generator, it should be fine - a generator is cheaper than a large battery bank, and propane stores well.

Building the whole thing myself, with the exception of what's required by code to be done by an electrician, I'm looking at having the entire system built for less than the cost of grid tied solar - but, this is also probably a month of work for everything, with pouring concrete, digging holes, etc.  If not longer.  Quite the project.

So, hopefully that (and the linked writing I've done) gives you a bit more information than you had.  I'm happy to answer questions.

[FIRE47]

Synonym I guess my main questions to you would be with regard to the battery system. I never intended to go off grid but I want to do solar and the way net metering works here and combined with the subsidy it just makes more sense.

My system will be well designed at least as well as can reasonably be assumed as in order to qualify I have to use gov approved design and installation and have them sign off. So I’m a best case the batteries only last 10 years? Right now they are paying $370 per kWh for battery system replacement as well I don’t know if that will be around in 10 years though. My hope is batteries will keep coming down in price?

 Between the fixed charges and triple the subsidy plus battery replacement they are practically begging me to pull the plug. being able to be self sufficient a goal I am slowly working towards (I also plan on going electric with my vehicle and going geothermal heat pump when my furnace goes) along with other more homestead type projects but I know those will basically double my current electrical  useaage. The numbers for return and the subsidy scales so the upfront cost only changes slightly when I increase the size of my system.

[BrickByBrick]

We live in an area that has commercial solar farms, so that was a strong indication to me that the numbers should stack up.

Unless you live in California/the Southwest I wouldn't immediately assume that.  I work for a large utility that is building a lot of solar farms, even if they don't make much sense from an efficiency standpoint in some locations.  But...those sweet, sweet tax credits though...

[PatronWizard11]

getting a $30k system 55% paid for by the government (state/federal) was the only reason we went solar a 2 years ago. we would not have made the decision if it wasn't for that. our solar covers about 75% of our electricity. Unfortunately I live in the most expensive electric rate county in the entire country but luckily solar helps me not to notice

[gooki]

Do your fixed charges drop if you change electricity plans.

Where I live high user plan has a fixed charge of $1.10 per day. where as a low user plan has a fixed charge of $0.34 per day.

[Syonyk]

Synonym I guess my main questions to you would be with regard to the battery system. I never intended to go off grid but I want to do solar and the way net metering works here and combined with the subsidy it just makes more sense.

If you don't care about off grid use, and are fine with the solar not working with grid power down, then just go with grid tied, net metered, and call it good.  Or install a transfer switch and generator.

My system will be well designed at least as well as can reasonably be assumed as in order to qualify I have to use gov approved design and installation and have them sign off. So I’m a best case the batteries only last 10 years? Right now they are paying $370 per kWh for battery system replacement as well I don’t know if that will be around in 10 years though. My hope is batteries will keep coming down in price?

Well, then, go with what they offer, since that's your option.  I can't offer too much advice on a government approved system without knowing what's in it.  It's probably adequate but not amazing.

Battery type, cost, and life varies wildly.  The new hotness is lithium (Tesla's Powerwall, LG Chem has some, Sonnen makes some, etc), and they tend to be stunningly expensive for what they offer (if you can get them - otherwise they're not on a useful delivery schedule), supposedly offer very long life, and can be cycled deeply on a regular basis, which is fine if you're grid tied, but isn't as useful off grid.

Most off grid power systems still use some variant of lead acid, and the right answer if you're dealing with it full time is flooded lead acid.  They're fairly well understood, they tolerate overcharging quite well (which is far, far better for lead than undercharging), and all you have to do is water them every so often, check the specific gravity on occasion, and try not to abuse them.

Off grid power simply doesn't deeply cycle the batteries, most of the year, if the system is well designed.  If you have enough panel for most of winter, the system will be quite full most of the spring/summer/fall, and will only get deeply drained in the winter.  So lead acid's love of being fully charged is perfect.  You have to really pull back the max charging voltage on lithium in this sort of service to get long calendar life.

The life of lead acid depends, to a solid approximation, on the cost of the battery in the first place.  You can buy cheap batteries that won't last two years, or you can buy high end industrial solar batteries with a 17 year design lifespan (for quite a bit more money, of course).

Then keep them cold, because hotter temperatures wear batteries out faster (of any chemistry).  This is a problem with my office setup and something I want to address at some point - my battery bank runs hotter than I'd like during the summer and I don't have a good way to cool it.  That it's in a non-insulated deck box has something to do with the problem...

Between the fixed charges and triple the subsidy plus battery replacement they are practically begging me to pull the plug. being able to be self sufficient a goal I am slowly working towards (I also plan on going electric with my vehicle and going geothermal heat pump when my furnace goes) along with other more homestead type projects but I know those will basically double my current electrical  useaage. The numbers for return and the subsidy scales so the upfront cost only changes slightly when I increase the size of my system.

If you're OK with expensive, maintenance intensive (relative to the grid), environmentally awful power, off grid is just fine.  You pay the cost in batteries instead of to the power company, and even with silly subsidies, you're going to have a far higher cost per kWh delivered, and you'd better enjoy generator maintenance.

Me?  I'm fine with that stuff, so I'm working to design a system that can run sustained off grid, and I'll probably experiment with sustained off grid running with the house, but I'm weird.  See the 20-30k words I've written about off grid power and batteries linked above.

[gooki]

Assuming your prices are US dollars, that subsidy is huge. $30,000 should easily get you a 10kw solar install and a Tesla Powerwall 2.

With a $3,000 per KW subside, that'd make the whole system free to go off grid.

Note your power requirements might be more that the above system would allow. Either way is there a limit to the subsidy? How big can you go?

[gooki]

Battery type, cost, and life varies wildly.  The new hotness is lithium (Tesla's Powerwall, LG Chem has some, Sonnen makes some, etc), and they tend to be stunningly expensive for what they offer.

FWIW where I live the Tesla powerwall is 1/2 to 1/3rd the price of LG Chen/Panasonic lithium battery solutions.

[Syonyk]

Assuming your prices are US dollars, that subsidy is huge. $30,000 should easily get you a 10kw solar install and a Tesla Powerwall 2.

Plus backup generator, fuel storage, control systems...

At least for quotes I've seen, $30k (US) will get you a 10kW grid tied system with no battery of any sort.  Batteries are another chunk of the cost.

And 10kW will generate plenty of power in the summer, but certainly not the winter.  So either you're using a ton of generator, or you put in a lot more panel.  On really bad solar days, for reference, my 2280W of primary panels will peak out around 150W and generate, on the worst days, about 300Wh all day long.  So... lots of generator use for my office, and I'm not asking it to run that many loads overnight.  I also heat on propane in the winter out there, because I don't have the surplus electricity to run anything for thermal management.  A ground source heat pump is nice, but if you're generating 1-2kWh/day on solar, that PowerWall isn't going to run the heat pump for long.  And I'll let you do the math on the efficiency of a heat pump running off a gas/diesel generator (the little ones are about 15% efficient if you squint hard, maybe a bit more on a diesel, but they're hard to start in the winter).  You're better off burning the fuel for heat.

Do you actually know people living off grid with a 10kW system and PowerWall, or is this just a hypothetical based on what you've seen?

FWIW where I live the Tesla powerwall is 1/2 to 1/3rd the price of LG Chen/Panasonic lithium battery solutions.

And you can't get one, at least in the US.

Here, I'll sell you a 50kWh battery for $1000.  Send me $500 for a preorder, and I'll let you know when I'm ready to ship it, with no guarantees on anything beyond that point.

The LG Chem battery is at least available, such that I could plan a system around it and have some target in service date.  The Powerwall is not.  Which makes it quite useless.  And you'd need multiple of them for any sort of off grid system, then you won't cycle them much most of the year because the summer months are a surplus of sun.

[gooki]

At least for quotes I've seen, $30k (US) will get you a 10kW grid tied system with no battery of any sort.  Batteries are another chunk of the cost.

Wow, any idea why the price is so high? Are incentives distorting the price, and going directly to the installer as pure profit instead of reducing the price to the consumer? FWIW I’ve seen this happen in other industries.

In NZ, we’re at the bottom of the earth, with little economies of scale, 15% sales tax, and stringent electrical standards, inspection requirements, and no solar incentives. My 4.5kw grid tied solar setup cost $7,000 USD (Monocrystalline panels with 25 year output guarantee, 5kw inverter with 10 year warranty).

10kw should be $15,000.

Tesla Powerwall 2 is another $8000 USD installed (inc 15% sales tax), so all up I’d be expecting $23,000 for a 10kw system with a 14kw battery.

I see the Powerwall 2 is $5,900 in the USA.

[gooki]

On really bad solar days, for reference, my 2280W of primary panels will peak out around 150W and generate, on the worst days, about 300Wh all day long

My worst day has been 1/2 my system size. I understand snow would have a more significant impact.

Typical grey and rainy day is 1x system size.

Typical grey day is 2x system size.

Partially cloudy is 3-4x system size.

Sunny is 4-6x system size.

And 10kW will generate plenty of power in the summer, but certainly not the winter.  So either you're using a ton of generator, or you put in a lot more panel.

That greatly depends on many things. Insulation, method of space heating, method of water heating, cooking. If off grid is the goal then optimising these parts offer significant energy reductions, or can be switched to other sources.

But I agree. I’d personally expect to have approx 2x battery size in panels.

[Syonyk]

At least for quotes I've seen, $30k (US) will get you a 10kW grid tied system with no battery of any sort.  Batteries are another chunk of the cost.

Wow, any idea why the price is so high? Are incentives distorting the price, and going directly to the installer as pure profit instead of reducing the price to the consumer? FWIW I’ve seen this happen in other industries.

Quite honestly, I have no idea.  I just know that $30k for a 10kW grid tied system seems about right out here, from quotes I've gotten and from quotes other people have gotten.  They can't exactly explain it either, it's just what their pricing calculators spit out... I think it's obscene.  I can do the math on panel cost, optimizer cost, etc, and... I still have no idea where they come up with $30k. 

10kw should be $15,000.

I'd agree.  That's reasonable.  I'm looking at 14kW panel, with batteries, for around $30k, doing the work myself.

I see the Powerwall 2 is $5,900 in the USA.

Yeah, but as I said above, that's a useless metric.  It could be $500, it could be $40,000, it wouldn't matter a bit, because you cannot get one.  They also don't interoperate with many of the systems designed for battery use, and installers tend to want a lot of money to work with them.

My worst day has been 1/2 my system size. I understand snow would have a more significant impact.

That's without snow.  That's just inversions, which are a super thick cloud layer (and, by definition, no wind at all).  Generator weeks.

That greatly depends on many things. Insulation, method of space heating, method of water heating, cooking. If off grid is the goal then optimising these parts offer significant energy reductions, or can be switched to other sources.

But I agree. I’d personally expect to have approx 2x battery size in panels.

If you're designing an off grid house, absolutely.  I agree, and you optimize the other stuff.  But the context here is trying to take a normal house off grid, and that's not likely to work terribly well.

It's certainly doable, and I intend to do it, but I also don't care a tiny bit about saving money with my system.  I care about resilience and creating goofy things.

[gooki]

If you're designing an off grid house, absolutely.  I agree, and you optimize the other stuff.  But the context here is trying to take a normal house off grid, and that's not likely to work terribly well.

Grid tied is definitely the simpler solution if the house is already connected. But if the incentive is $3,000 per KW for off grid. I'd be exploring those options.

[FIRE47]

At least for quotes I've seen, $30k (US) will get you a 10kW grid tied system with no battery of any sort.  Batteries are another chunk of the cost.

Wow, any idea why the price is so high? Are incentives distorting the price, and going directly to the installer as pure profit instead of reducing the price to the consumer? FWIW I’ve seen this happen in other industries.

Quite honestly, I have no idea.  I just know that $30k for a 10kW grid tied system seems about right out here, from quotes I've gotten and from quotes other people have gotten.  They can't exactly explain it either, it's just what their pricing calculators spit out... I think it's obscene.  I can do the math on panel cost, optimizer cost, etc, and... I still have no idea where they come up with $30k. 

10kw should be $15,000.

I'd agree.  That's reasonable.  I'm looking at 14kW panel, with batteries, for around $30k, doing the work myself.

I see the Powerwall 2 is $5,900 in the USA.

Yeah, but as I said above, that's a useless metric.  It could be $500, it could be $40,000, it wouldn't matter a bit, because you cannot get one.  They also don't interoperate with many of the systems designed for battery use, and installers tend to want a lot of money to work with them.

My worst day has been 1/2 my system size. I understand snow would have a more significant impact.

That's without snow.  That's just inversions, which are a super thick cloud layer (and, by definition, no wind at all).  Generator weeks.

That greatly depends on many things. Insulation, method of space heating, method of water heating, cooking. If off grid is the goal then optimising these parts offer significant energy reductions, or can be switched to other sources.

But I agree. I’d personally expect to have approx 2x battery size in panels.

If you're designing an off grid house, absolutely.  I agree, and you optimize the other stuff.  But the context here is trying to take a normal house off grid, and that's not likely to work terribly well.

It's certainly doable, and I intend to do it, but I also don't care a tiny bit about saving money with my system.  I care about resilience and creating goofy things.

I appreciate the realistic views on doing this and I need to learn a lot before going ahead with this, which won't be a problem this sort of a thing is right up my alley - in fact the reason I am doing it is not to save money although with the subsidy it may do that. The fact is though my home is not the average suburban home. I only use about 5,400 kwh a year and heat my house and hot water with natural gas. I have a very large South and ESE facing roof at a great angle that is also so high nothing will ever shade it (until the sun sets over the opposite side obviously) and $3k per KW of government money to set this up. I realize that I have a lot to learn but if I can't do it with these conditions I don't know who can. At the end of the day I can always just reconnect and I lose a few thousand dollars in batteries and other equipment and just go with net metering with a backup system for power outsages.

[Syonyk]

What government is offering people $3k/kW to help kill the power grid?  That still seems insane to me. :/

You can do it, if you want.  Not going to argue there.  But just make sure you read up on off grid living before you go in, and make sure your generator is in good shape.

[FIRE47]

What government is offering people $3k/kW to help kill the power grid?  That still seems insane to me. :/

You can do it, if you want.  Not going to argue there.  But just make sure you read up on off grid living before you go in, and make sure your generator is in good shape.

https://greenon.ca/programs/GreenON-Solar-Rebates

There are also other gems like $20k to install geothermal and $500 per window to replace your windows with more efficient ones. I have already gotten a free NEST thermostat just as their kickoff of the program ordoeuvre.

This is where the carbon tax money or some of it is going.

[FIRE47]

What government is offering people $3k/kW to help kill the power grid?  That still seems insane to me. :/

You can do it, if you want.  Not going to argue there.  But just make sure you read up on off grid living before you go in, and make sure your generator is in good shape.

After looking at the long-term and more accurate numbers even assuming the battery replacement subsidy exists in 10 years (I highly doubt it) and even with the generous upfront subsidy going off the grid would barely pay for itself while being a massive pain in the ass. The better bet is just to net meter with the smaller subsidy, enjoy the 8-9% return over the long-term (more if the panels last beyond 25 years) and perhaps add some limited capability for when the power goes out to scratch that itch while still being tied into the grid (they do give an extra $500 per KW for that). Realistically I'm not going to bother with dealing with flooded lead acid on a regular basis so it's going to cost a lot to keep myself in batteries.

[Syonyk]

Seems wise.

As I pointed out in my article on off grid systems:

Answer this question: "How do I feel about the concept of designing and operating my very own multi-source power generation and storage facility?"  That's what an off grid power system is - it's a reasonably complicated power plant, but with the added complexity of storage (and the plant is radically too small to get any sort of decent efficiency).  For some people (including myself), this concept makes them giggle with joy.  It sounds awesome!  You get to monitor generation, use, storage, check the frequency and voltage, and have an excuse to buy all sorts of cool shunts and meters!  For other people, it sounds like a circle of Hell.  They just want to flip the switch and have the lights turn on.  Or push a button and have the kettle warm the water for their tea.