Is My Roof Right?

Determining whether solar makes sense…

Shade Considerations

The final consideration for a roof is shade. Much of Northern California is wooded and hilly and a real weakness of solar panels is that just a bit of shade on a panel or two really ruins production. Not just for that panel, but for all panels connected to that panel (sort of like one bad battery in a flashlight).

There are five factors that might mean that your shady house is still a contender for solar:

  1. Morning and late afternoon shade does not matter compared to mid-day shade.
  2. Winter shade does not matter compared to summer shade.
  3. Solar requires only a portion of your roof, so perhaps some of your roof has good sun.
  4. Devices — MPPT optimizers — can be added to your panels, so shade on one or more impacts just those panels.
  5. A high PG&E bill (meaning a lot of tier 3 and tier 4 electricity) means that a shade-hindered system that wouldn’t make financial sense for someone using less electricity might make sense for you.

But if you have midday shade, don’t let someone sell you a solar system unless you study the numbers, and really understand how it makes sense for you.

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