Slacy’s Blog

California Solar Power History

As we enter the depths of California winter (sic!) our solar system is producing less and less energy. We’re seeing severe shading for most of the day (after about 11am) and that cuts our production to only a couple hundred watts on a sunny day. The funny thing is that if there’s just the right amount of haze (not too much!) then the panels can collect more ambient light, and aren’t as effected by the shading. So, the best days for generation are sunny in the morning, and hazy in the afternoon. On days like that, we produce about 4.5kWh, or about 1/4 of our daily electricity usage.

On the other hand, the worst possible day is hazy in the morning and sunny in the afternoon, and thats a fairly common weather pattern for us here in the Bay Area. Thats almost exactly what happened today, and we had our lowest output ever, at a measly 2.27kWh. Thats hardly enough electricity to power one TiVo for the day!

Thankfully, we’re approaching the winter solstice on December 21st, and that’s when the shadows start moving back in the other direction, giving us more and more energy. But, that also means that January will be just as bad as November, so it will be another 60 days or more until we see a significant increase in production.

I was walking by our electricity meter the other day, and noticed that it read “50,000 kWh” — the same number that it read when it was installed about six months ago! So, I took a photo! Since fall, we’ve been producing a lot less electricity. Partly because of the baby (more laundry, and generally more ‘use’ for the house) but the even bigger impact is the shade thats hitting our panels and cutting out production for most of the afternoon.

This is exactly what we expected — the SolarCity installer originally predicted that in the month of December, we’ll only have 37% of our possible production due to shading. Thankfully, we’ve built up >$300 credit with PG&E, and now we can start to use up that credit.

I still expect us to be nearly “net $0″ for the year, but its looking less likely that we’ll be “net 0kWh” for the year.