Review of the Solar System

The past couple of weeks have been interesting to see how the power from solar cells varies with clouds, rain, and sunshine. In the first part of November, I got about 35 Kwh of power on a sunny day. Now, with shorter days, I'm getting about 28-31 Kwh. On overcast days, the output of the cells ranges from 4 Kwh to around 15 Kwh.

One decision we have concerns the use of electricity vs. gas for heat. During days with lots of sun, we used electric space heaters and during overcast days we used gas (the furnace burns gas for heat but uses electricity to run the fan). I haven't figured out yet an objective way of comparing the two. We've had a lot of overcast days the past two weeks, and we've been using more electricity from the grid than we get from our solar cells. Right how, there is a difference of 163 Kwh. There was a larger difference this morning, but today was a sunny day with no clouds, and that reduced the difference. The next two days are forecast to be sunny days with rain forecast for Saturday and Sunday, and the next two days should reduce the difference by 30 Kwh or so.

I pay about $0.12 per Kwh, so difference of 200 Kwh would mean about $24.00 on my power bill. I'll be paying $6.00 for a fixed monthly fee, making my monthly bill about $31.00, a big difference from the average of $120.00 that I've been paying. When my bill comes in the first week in December, I'll have a better idea of how the dollars work out. Hope we have a lot of sunshine between now and the first part of December. We should get a lot of power next summer when the days are longer and the sun is higher in the sky. We're hoping we can turn our AC down to 76 and still build up a good reserve for the fall and early winter.

We had about an inch of snow a few days ago, and the snow really reduced the power from the cells. Yesterday, we looked at the cells, and they were free of snow, but there was snow on the roof at the lower edge of the cells. It looked like the snow slid off the cells onto the roof. My wife  thought she saw dust on the cells a few days ago, and we're hoping the rain and snow helped remove the dust. The rovers on Mars use solar power, and dust really affects the power output of their cells.