Thoughts on sizing/installing a smallish residential solar system? (N Calif)

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curmudgeon
Posts: 1631
Joined: Thu Jun 20, 2013 11:00 pm

Thoughts on sizing/installing a smallish residential solar system? (N Calif)

Post by curmudgeon » Sat Nov 10, 2018 4:46 pm

Despite having high electric rates and good sun, I have held off on installing solar because I didn't want to do it on a roof that would need replacing soon. I'm getting closer to doing the roof, and so I'm trying to evaluate solar options as well. Our electric usage is pretty light, 200-250 kwh most months, but it can jump to ~800 kwh or more in a month if we have a block of really hot weather like we had two years ago. We are paying 22-28 cents/kwh these days, and I worry about getting stuck with ever-higher rates as the politics and economics of the system continue to evolve in CA. It's quite possible we might increase our usage a notch, add a hot tub, use A/C more. On the flip side, at some point we'll probably have to replace the old inefficient A/C, and we may add wall insulation.

Currently there is a $10/month minimum charge for grid tie (which I think is actually pretty cheap), and net metering still available. If we used power like we did this past year, the max savings would only be about $550/year, hardly worth the nuisance and cost of installing, monitoring, and maintaining the system. But some hot summers or additional usage might drive the savings toward $1000/year, which could be more relevant.

We will probably be here at least five more years, beyond that is unclear. I would only want to do an owned system, no leases or other creative financing. I won't fret too much about the residual value if/when we sell.

I'm presumably looking at around a 2 KW system. I want something robust and that won't need a lot of monitoring (I've read a few stories of people losing the inverter and not realizing until they got a massive bill at the once-yearly "true-up"), so it seems like micro-inverters might be appropriate.

If you have specific recommendations for companies to consider (or avoid) in Bay area (San Jose), I'd be interested. Also any general thoughts on selecting an installer.

If you have thoughts on whether economies of scale for installation/permitting would be a reason to go a bit larger, that would be helpful too.

Our new roof will likely be standard heavy asphalt shingles. I'm not sure if there are any special considerations I should have when planning ahead for the solar install.

quantAndHold
Posts: 1884
Joined: Thu Sep 17, 2015 10:39 pm

Re: Thoughts on sizing/installing a smallish residential solar system? (N Calif)

Post by quantAndHold » Sat Nov 10, 2018 6:16 pm

We’ve had a 2.4kW system in Southern California for the past ten years. They installed it (you are correct, they won’t even install it on an old roof), and it does its thing. Other than washing the panels every year or two, we don’t do anything. The inverter is in a location where we walk past it regularly. The one time we blew a fuse, we noticed that there was a red light blinking and got someone to look at it.

Solar companies can look at your last year’s bill and tell you what size your system needs to be to be most cost effective. With net metering, you’re trying to generate slightly less than you use over the course of the year, because system pricing is based strongly on how much power the system generates, and you don’t want to pay for extra capacity and give the power company free electricity. We got three estimates. They all recommended the same size system, and they were pretty much correct. We generate about 90% of what we use.

curmudgeon
Posts: 1631
Joined: Thu Jun 20, 2013 11:00 pm

Re: Thoughts on sizing/installing a smallish residential solar system? (N Calif)

Post by curmudgeon » Sun Nov 11, 2018 1:30 pm

quantAndHold wrote:
Sat Nov 10, 2018 6:16 pm
We’ve had a 2.4kW system in Southern California for the past ten years. They installed it (you are correct, they won’t even install it on an old roof), and it does its thing. Other than washing the panels every year or two, we don’t do anything. The inverter is in a location where we walk past it regularly. The one time we blew a fuse, we noticed that there was a red light blinking and got someone to look at it.

Solar companies can look at your last year’s bill and tell you what size your system needs to be to be most cost effective. With net metering, you’re trying to generate slightly less than you use over the course of the year, because system pricing is based strongly on how much power the system generates, and you don’t want to pay for extra capacity and give the power company free electricity. We got three estimates. They all recommended the same size system, and they were pretty much correct. We generate about 90% of what we use.
If the inverter has a obvious "failed" signal, that would be good. Something more than an lcd display that might not be noticed. The logical place for an inverter at our house would be right by where we keep the trash cans, so I guess a single inverter (instead of micro-inverters) might be OK in that respect.

I debate a bit about sizing because of the weather variation. This past year had very little A/C usage, but years with long hot spells could add 50% to our yearly total. Extra generation yields very little, if any, value in power sales, but would be more valuable if our usage is high or goes up from adding a hot tub (or maybe even an electric car). Once you are doing the permitting and install, I would think a couple extra panels shouldn't add that much to the cost these days.

Typ997S
Posts: 20
Joined: Fri Apr 06, 2012 12:36 pm

Re: Thoughts on sizing/installing a smallish residential solar system? (N Calif)

Post by Typ997S » Sun Nov 11, 2018 3:23 pm

Hi Curmudgeon - Based on your post, I would say you already have a very comprehensive understanding of the trades to be made when installing a solar power system. I think you are correct that you are not going to see a large economic benefit because your current power usage is so low (congratulations!)

I'm in San Jose too, and as you know our climate, with 300+ days of sun a year is very favorable to solar. I have a relatively large system, 7.7 kW DC / ~6.3 kW AC peak, because I have a large 2 story house with 5 occupants and a plug-in hybrid car. My system was installed by Vista Solar in 2009. They did a great job (didn't hurt that the CEO lived across the street,) but unfortunately they only do commercial installs now. As far as choosing an installer, I'd suggest getting 3 or so bids. If you prefer one of the installers, try to get them to match the low bidders price. That worked for me...

Regarding the Inverter and System Monitoring - I think most companies will offer a service to monitor the performance of the system, usually for a fee after a free period to start. As far as failures, I have not had any within the power generation system in the 8 years the system has been operating. I did have a electronic board fail in the monitoring box, which cost $500 to replace.

And since you mentioned having the Inverter near garbage cans, my only other "outage" involved a garbage can! When rolling out the trash, the rotary isolation switch on the bottom feed to the inverter got bumped and turned the system off. It took me a few days to notice. So, watch out for trash cans!

Good luck, and shoot me a note if you have any other questions about my experience so far with solar.

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