Your experience with solar power
November 17, 2013 12:58 PM   Subscribe

We're seriously contemplating installing a PV system on our roof. Any experience you've had with this process would be most appreciated.

I'd be particularly interested in hearing about the installation (what surprise costs were there? did it damage your roof? uglify your house? did you squeeze in other work at the same time? did you need to trim trees or make other pre-installation changes? did it take long?), the maintenance (what has gone wrong? do you need to get the panels cleaned? does debris collect under them? does the house get hotter in the summer having black panels all over it? what components have broken?) and whether the initial calculations (of energy produced, money saved) were about right.

I realize that the finances will be totally different for each project, so I'm not expecting a go/no-go analysis on that end. But if your estimates were wildly off I'd love to hear why, and in what direction. (For example, my initial calculations show us producing ten times as much electricity as we consume. This makes me very skeptical. Was this your experience?)

I'm in Washington State, so if you have experience here, that would be especially helpful, but really, everyone's experience is valuable (including people who investigated PV and didn't install it for some reason).

[The specifics of my installation aren't really that important, because I haven't made up my mind on a number of things, so just a description of what you did is fine. You don't need to tailor it to my situation for it to be valuable to me. Thanks.]
posted by Capri to Home & Garden (7 answers total) 7 users marked this as a favorite
 
I haven't installed a solar PV system, but I know that if your calculations are showing you producing 10 times your consumption, something is wrong. This is not possible with current technology.

Can you post your calculations in a spreadsheet?
posted by ssg at 1:16 PM on November 17, 2013


My parents — who live in spectacularly rainy and far-north Glasgow, with a system that's facing not quite the right way due to the way their house sits — are getting pretty much what they expected from it, with no downsides in the couple of years it has been running. (That's partly because I had access to PVsyst at the time, and ran a full detailed system analysis, which came in with a very slightly lower annual yield than the contractor had said.)

Does Solar Prospector come up with the 10× demand number? It's a pretty decent estimator for North America if you don't have PVSyst.
posted by scruss at 2:17 PM on November 17, 2013


Get the last few issues of Home Power magazine and read through them.

I just had my whole house reroofed, because it needed it, but also because I'm going to put a PV installation up and obviously that shouldn't be done on a roof that's going to need reshingling. While they were reroofing, I had them put moisture barrier under the future panel locations (and thus bolt penetrations) instead of the usual 30 pound felt.

As the price of solar panels comes down, the "balance of system" components (every besides the actual panels) is starting to take up a bigger and bigger share of

Get the last few issues of Home Power magazine and read through them.

As for the 10X error that everyone else is latching onto, possible mistakes you are making are:
- not accounting for cosine losses (morning light is far weaker than midday)
- not accounting for cloud cover statistics
- not accounting for panel / inverter inefficiency and other losses

This gets pretty complex so why don't you just get a professional solar installer to come out and quote for you? Ask him to make shading measurements. They have a neat tool that can figure out the shading in one 10-minute measurement. From that he'll be able to calculate your production.

Get the last few issues of Home Power magazine and read through them.

The most recent issue had an article on evaluating existing PV installations, e.g. when looking at buying a house that already has PV. Obviously you aren't doing that, but I found the article extremely interesting (the clipping went into the PV project folder) because it showed how things can break down, and contractors can cut corners.
posted by intermod at 3:57 PM on November 17, 2013


The 10 X your consumption does seem unlikely and is probably erroneous, though it's not impossible if you use modest amounts of power and install a large system. For example, if you use 2kWhr (kilowatt hours) per day and install a 5kW system, it would produce 20kWhr per day on average in southern Australia. Not sure about Washington State, but guess it might be less. 2kWhr per day is very low consumption though. 20kWhr per day would be more common here, but it does vary quite a bit and I know people who use less than 2kWhr a day.

Ugly is pretty subjective, so it's impossible to say whether it will detract from the appearance of your house. Having modules mounted flat on the roof is the least obtrusive and is generally the way it's done here.

It's best to mount the array somewhere where it won't get shaded as small amounts of shade can reduce the output significantly. That may involve trimming trees.

Good quality systems should require little or no attention. You may need to wash the array occasionally if you go for long periods without rain. Debris shouldn't collect if the modules are mounted off the roof a little, which they should be.

If anything, I think the solar modules would reduce the summer heat into the house because they shield the roof and should dissipate a lot of the heat they catch. It would depend on the situation though.

FWIW, I would put most of my energy toward researching installers if I were thinking of buying. A good installer will give you good, specific answers to all these questions and be able to work with you to get the best outcome.

Full disclosure: I run a solar installation business.
posted by mewsic at 4:49 PM on November 17, 2013


We went with Solar City and did the "no money down 'lease'" option. It was great. We did that instead of buying the system outright because we're not sure how long we'll be here. I think my preference would be to do the "prepay lease" option where you buy the electricity ahead of time but they still own, monitor, and are responsible for fixing the equipment.

as I see it, there's really no downside if your siting is right.
posted by reddot at 5:51 PM on November 17, 2013


I had a 2650-watt system installed on my roof in Seattle through A & R Solar. It was completely painless. Installation took a day and a half, plus another day and a half added because I also had them upgrade my service panel to 200 amps and move it outside (it had been on the wall in the downstairs bedroom, which was inconvenient). There's a bunch of hardware on the side of the house now, which you can't see unless you are standing in the side yard. You can see the edge of the array peeking over the ridgeline of the house from the street, but I think it looks kinda cool.

We did have to get a tree trimmed back; cost about $250.

This was my first summer in the house so I don't know how it would have been with no panels, but they're pretty much opaque, and there's an air gap between the panels and the roof. If anything I'd guess they kept the house a mite cooler.
posted by Mars Saxman at 8:43 PM on November 17, 2013


We had a 2.4 kw PV system installed in Feb 2010. If I have time later I'll speak in more detail about our experience, but in the meantime you can see what that means in terms of actual output (more like 1-2 kw), seasonality, etc by checking out the system's Enphase site. You can view systems in Washington state by zooming in on the all public systems page.
posted by 0 at 9:04 AM on November 18, 2013


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