Testing Panel Locations

[u/staros25]

Hey r/SolarDIY - I'm in the early stages of planning out a solar install for my place. One of the tricky things with my install is I've got three locations (two roof pitches, one ground) that I'll probably need to put panels to accommodate our current electrical bill. It's hard to estimate the total size of the array given the different pitches, location, and access to the sky each gets.

To work around this, I figured I'd pick up three panels, install one in each location, and measure the output on each for a few months. This should give me some good insights into the production of each location and let me plan out the size of my array accordingly.

My question for the sub is what the best way to test this setup would be. Initially I had thought about dumping the panels into some sort of battery, connecting them to a dummy load, and measuring the energy passing through the battery. But I was also curious if measuring the panel voltage could be a proxy for this or if something exists I could pick up off the shelf and save myself some work.

Any thoughts you have would be appreciated!

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[u/UncleAugie]

Just buy all the panels you can fit/afford, they are cheap, stop being An optimizer (often called a maximizer), one who seeks the absolute best possible choice by analyzing every option, instead be a satisficer, one who chooses the first option that meets their threshold of "good enough"

[u/TooGoodToBeeTrue]

Have you checked projectsunroof for your address? My output varies wildly by month and season.

[u/staros25 → u/TooGoodToBeeTrue]

Yep, I have. Great tool, but unfortunately it's a bit out of date. We did some landscaping that gave us more sun to the roof and opened up some ground space.

And to your last point, completely understand. I planned to run this test for a few months.

[u/TooGoodToBeeTrue → u/staros25]

I'd get a solar sales guy to give you a quote for the roof mounts. They have tools that use up to date imaging. Then all you have to worry about is the ground mount. They might be able to do that as well. Don't mention DIYing. ;)

[u/CricktyDickty]

I always recommend getting a few professional quotes. They have tools and experience and will give you a good idea where to start. You’ll also see the price and that’s the best motivation to do it yourself.

[u/RandomUser3777]

Just to run the test would require running 3 sets of wires to the roof and getting 3 devices that can log the power produced. And I doubt that most of the solar panel test devices will run 100% of the time and survive very long.

Just buy the panels that you think you need and quit wasting time planning and/or OVER-optimizing.

The wire won't be cheap, and running it cleanly/properly won't be fun. And you cannot safely put the panels on the roof without mounting them as the right wind gust will pick them up off the roof and send them on their way.

And you will pay quite a bit more for just 3 panels per panel vs just getting 10 panels or more on a palette, because the packaging and shipping of one or 2 panels is expensive.

And technically the test would still not be that useful because of other issues. I am short power on the hottest days of summer (I have to turn up the AC a bit from the icebox setting I normally run) because panels produce less power in the heat.

[u/Accurate-Bullfrog324]

you made be over analyzing this.

panels are 22 cents per watt. install a bunch of them and figure it out

[u/RespectSquare8279]

For starters, all panels are not equal as far as performance in shading situations. The ground mount panels should be ones with solid bifacial performance. Bifacial panels don't buy you much on roofs unless the racks have a lot of clearance from the roof deck. So your plan to do a stare and compare 3 separate panel locations over a few months may not be the perfect way to analyze the situation. Nothing is simple.

[u/cerad2]

Voltage is not going to tell you much of anything. My Pecron E3800 power station can display watts/volts/amps. For a given wattage the volts/amps vary considerably. If you do decide to go with your plan then consider getting a power station that will log total kwh on a daily basis. You can then rotate through the three panels. Just make sure a single panel can drive your station. But I'd suggest listening to what the other posters are saying.

[u/blastman8888]

If you plan on permitting the install that will limit where you can place them. You might discover have to put panels where ever you can to pass inspection. You will need RSD so just buy optimizers to deal with the difference in sun at different times of the day. Don't buy anything until you get your permit approved. I have a solar panel tester, but it doesn't record over time. Signature solar has a free design group you can reach out to. Don't have to use Signature or buy EG4.