Author Topic: Solar Panel Installation?  (Read 951 times)


  • Pencil Stache
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Solar Panel Installation?
« on: October 03, 2018, 09:37:10 PM »
Advice needed. We live in Northern California (greater Sacramento area) with great sun exposure and lots of AC usage. We purchased a new high-end HVAC system in May that did an excellent job this summer. The previous 12 months energy usage was only 5,050kwh for a 2,300 sq. ft. house. With the big HVAC upgrade, I expect our annual consumption to decrease even further as October through May were with the older HVAC system that was not nearly as efficient, however, it is difficult to quantify at this point.

With that said, I want to purchase solar panels for both financial reasons and environmental reasons. I'm hugely incentivized to do this by the end of 2019 to take advantage of the 30% tax credit before it gets slightly reduced. I plan to purchase outright and pay cash. I will not be financing, and I definitely won't be leasing or doing any type of power purchase arrangement nonsense where I don't own the panels.

Having said that, I've shared my detailed month-by-month usage with a few vendors and they are ALL recommending a system that produces ~105% of our actual usage. When I used PG&E's solar tool, they recommended a system with only 85% of our usage. Obviously, each solar panel that you purchase costs more money, and has less marginal improvement based on PG&E's tiered pricing structure. Whenever I push on the sales rep about why they are suggesting such a big system, they always turn it around that they always recommend more than 100% so that we could get more comfortable and use more electricity and not have to worry. They are obviously incentivized to sell more panels, so I immediately have a distaste for their sales tactics.

With all that said, when I try to google how big of a system should I buy, I just get blasted with a slew of advertisements for different solar companies. I can't seem to find any unbiased advice. So, do you have any recommendations on where to find unbiased advice on solar system sizing? Or do you have any unbiased advice yourself?

Please share! Thanks in advance!


  • Pencil Stache
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Re: Solar Panel Installation?
« Reply #1 on: October 04, 2018, 10:34:23 AM »
We have a system on our rental, initially set up to cover 50% of the unit's usage. We plan to add on some day to get up to ~90%. Our utility has disincentives if you size the system for more than 100% of estimated usage.  The reimbursement rate tanks for any amount generated in excess of yearly total. Read the fine print.

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  • Walrus Stache
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Re: Solar Panel Installation?
« Reply #2 on: October 04, 2018, 10:41:29 AM »
We set up our solar system to account for 80% of our electric needs. The cost that electricity is bought back in our area is so low that we could not make our money back on the extra panels if we over-produce.


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Re: Solar Panel Installation?
« Reply #3 on: October 04, 2018, 11:20:21 AM »
I can't seem to find any unbiased advice. So, do you have any recommendations on where to find unbiased advice on solar system sizing? Or do you have any unbiased advice yourself?

Personally ran my own numbers based on the utilty's solar buyback rates and landed at a system sized to cover 100% of annual electricity (10 year payback, not stellar). Sounds like your tiered rate structure might make doing that analysis a bit complex.

Also used EnergySage (it's free, they help you get multiple quotes from reputable contractors and you get a free solar advisor on their staff to ask any questions).

Looks like might be a forum where you could post this type of question too.


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Re: Solar Panel Installation?
« Reply #4 on: October 04, 2018, 08:41:54 PM »
I'd recommend going for the <100% plan - you can always add in more panels in the future if your projections are significantly underestimating usage with the new system. The installation labor per panel will be higher and tax credits may expire. Some of that may offset by decreasing costs of the panels themselves.

Is your house maximally insulated? What is the R value of your wall and roof insulation? I would figure that out before buying a solar system. That will certainly save you more money and cost less than having a system projected to produce 100% of your current usage.
« Last Edit: October 04, 2018, 08:43:44 PM by Abe »


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Re: Solar Panel Installation?
« Reply #5 on: October 05, 2018, 10:01:42 PM »
Interesting. I live in CO and we are installing solar panels after having dealt with a few different contractors. They all tried to size the system a bit under 100% unless we claim we're going to get an electric car or something like that. The reason being is that here at least, you can't sell back excess credits above what you use at retail price. You can do it for monthly overage/underage within a year, but over the long-term, if you have to sell it back, you get something really lame like 0.02 $/kwh. So they try not to oversize the system. Maybe there's a good reason to oversize a system in CA, but I'm not sure what that would be.

A few things to keep in mind:

1. The cost of the panels themselves is rather low and getting lower all the time. There are large fixed costs like labor, permitting, new meters, etc. The marginal cost of an extra panel or two isn't that big of a deal. If they were to add them after the initial installation, it would cost way more. 

2. Most people (hopefully) will be using electric cars in about 10 years or so. It's not a bad idea to plan ahead for that. And it's possible that your hot water heater, HVAC, etc. might go electric too. (Though you just replaced the HVAC, so maybe not that.) Decarbonizing residential energy use is all about switching to electric.

3. You get the tax credit based on the price of the system. So, bigger system means more bang for the buck now, but the big question is just how much cheaper the panels get in the future. Plus whether or not grid electricity gets cheaper because of a surplus of utility-scale solar. How this will play out is not clear.

I don't have a straight answer for you, but ultimately you need to calculate what your ROI is for whatever system you're looking at. For us it's about 9-10%, which makes it a good investment even if we didn't care about anything else.