Shade from solar panels

Thinking about when Musk paved a parking lot with solar panels in Puerto Rico to get a hospital back online.

If I cover a roof (or I guess a parking lot, assuming they are off the ground so people can park under them) with solar panels, how much does shading the roof from direct sunlight help in keeping the building cool? I assume not a bunch, but on the other hand, trees do help keep a home cool, so the is the effect similar? Measurable?

It helps a bunch here. My building has a huge parking lot that’s covered by a structure with solar panels on top of it. The shade from that structure is huge in keeping the cars parked in the lot cooler. My own house has a covered patio structure that I built to both shade the west side of the house and provide solar panels that would always face the afternoon sun (I have panels on other parts of the house too). Not only do I get energy from them but they probably lower the interior temperature on the west side where we have a bunch of windows by at least 4-5 degrees C in the summer. It’s a very noticeable difference from before we put it up to now.

Will that raise your heating costs in Winter?

Probably a bit, as you inferred I get less sun in the winter in the house. But where I live the primary issue is cooling in the summer. My electric bill used to be over $400 in the summer months and it would drop substantially in the winter (part of that is we have a kiva fireplace inside as well as outside) and now it is a fraction of that in the summer without a noticeable increase in the winter.


If you’re really worried about heating in the winter, you can put up solar panels and then use them to power a heat pump. Since heat pumps can achieve “efficiencies” of greater than 100%, this should still be a net gain over not having the panels.

Of course, it might be even better yet, economically, to use gas heat, and use the electricity for other purposes that can’t use gas, depending on your local prices. But the point is, the panels can’t hurt, on net (other than the cost of installing them).

I thought cooling heat pumps were less efficient than A/C. This info is from the 1980s from a prof who had an HVAC company, so it is probably out of date. Can solar cells run a heat pump? That is a lot of current.

A cooling heat pump is an air conditioner. Though it may well be that a dedicated, single-purpose air conditioner is more efficient for that task than a dual-use heat pump which can heat or cool a house. In any event, a heating heat pump is more efficient than just using the same energy to produce heat directly.

I don’t know if there’s any commercial off-the-shelf heat pump that could run off of the amount of power produced by a rooftop’s worth of solar panels, but there’s no reason, in principle, why it couldn’t be done.

Trees transpire water (similar to perspiration) and therefore the shade of the tree is much cooler than any shade structure even solar panels.

Economically, you are better off installing window shades and a good AC to cool your house. The return on investment for Solar Panels is about 15-20 years depending on where you live, government incentives and grid rules.

The best return on investment is from window films that reflect light.

I’m not in a place where panels would likely pay off (a bit too far north considering the number of trees on the south side of my house). I was just curious about the shade effect as a (small) boost to the payback formula.