Just a quick entry today, with performance data from the first four weeks of my rooftop solar array. The news is both disappointing and hopeful.

During this time span, we used an average of 12.3 kWh per day, which is more than normal for this household. More on that in a moment. To meet that daily demand, just a tick more than half (6.2 kWh) came from solar power production. 6.1 kWh had to be purchased from the utility.

Over time, I think we’ll see the percentage of my electricity needs offset by solar go way up, from roughly 50% to closer to 100% or more. Here’s what I think happened:

  • Household demand was up due to wrapping up a remodeling project from the summer. Lots of power tools plugged in in the garage, and at one point a high-powered fan blowing 24/7. (Don’t ask…it had to be done.)
  • Solar production was weak for days at a time, as we got soaked with much higher than normal rainfall in October. What I’ve observed so far is that the array is of course highly productive on sunny days, surprisingly productive with the indirect light of partly-cloudy days, but scarcely productive at all on those wall-to-wall rainy days that the Pacific Northwest can sometimes have.

As we head in to the darkest weeks of the year now, it’s possible the array will offset even less of my overall electricity needs. But I knew this going in. Spring and summer of 2015 will be the big test.