Photovoltaic electricity is great stuff and we need lots more of it – but it does have shortcomings. A snowy December, when the sun is low on the horizon, has shown me (a new owner of PV rooftop panels) just how big the shortcomings can be.
The chart below shows the daily total production of my 18 solar panels so far in December.
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You shouldn’t draw conclusions from one year’s data. Weather varies from year to year. This is the third December that my solar panels have been operating and it is the worst year, so far. We are only 2/3 of the way through December, however, and it looks like it should be less cloudy over the next week or so. In contrast, last month was the best November that I’ve had so far. Things balance out. November & December are statistically the cloudiest months of the year, plus we are at about only 9 hours of sunlight, far below the day length in the middle of summer. To balance that off, however, solar panels are more efficient when it’s cold, so you should get better “per hour” production from your panels from now through February.
Net metering helps to balance this out, saving Kwh generated in mid summer for use at this time of year. As of today’s bill I have 1300 Kwh in the bank, which will easily get me through the lower generation winter months.