The numbers are in and the second year on solar was as good as the first.
In the first year, our solar panels produced 4,371 kilowatt hours of power. In 2012 they produced 4,279 kwh, a 2% drop. My understanding is that solar panels retain about 80% of their power for a 20 year period. So hopefully the dropoff will be less in coming years.
How about our electric bill?
In 2011 the bill was almost exactly zero. This year, the bill was even less—we showed a $50 negative amount (but that doesn't mean we get $50 back—see below). Our PG&E bill shows that we used 1,661 kwh. Adding that to the solar shows that we used 5,940 kwh of electricity this year compared to 6,460 kwh last year—520kwh less for the year. Not only did we use less, but we managed to use more electricity in the off-peak when it is cheap (about 5 cents per kwh) and less in the peak periods when it costs more (31 cents per kwh in the summer and 10 cents per kwh in the winter).
I'm not sure how we managed to do this but the result is that our bill showed that we gifted PG&E $50. Actually, since there is a minimum charge of about $5 per month, or $60 per year, we could have used an additional $110 of electricity with no charge. Therefore, on cold days this January, we've been using an electric heater in our bedroom and turning off the heat in the rest of the house at night. We do turn on the heat when we're using the rest of the house. We'll see next year if we zero out the electric bill.
Double pane windows
One other variable this year is that we added double pane windows to replace our leaky old wooden and aluminum windows. I estimate that this reduces our heat loss from the house by about 15%, so that means we need less gas to heat the house. But we still need some. I'll work on those calculations, but it is clear that the windows will never be "cost effective"—i.e. not counting the true cost of fossil fuels but only the low market price of natural gas. I don't regret adding the windows, but I don't expect everyone to run out and do that with the current price structure (I do think people should run out and buy solar panels and an electric car, however, as I repeatedly argue in this blog).
Conclusion
As I said last year at this time, “Everything is going according to plan,” to quote Emperor Palpatine. The solar production exceeded our expectation; the Volt cost 2 cents per mile to drive on electricity; and we cut our CO2 by over 70% compared to driving a car like our old Honda that got 25 mpg. Still we have a ways to go to be truly sustainable.
See last year's post: for more detailed calculations.
Why isn't everyone running out to buy solar panels?
Beats me! This year the deal is better than ever. With interest rates at 3.5% for a 30 year loan and the cost per kilowatt installed at $4.90, and including a 30% tax break, the cost per kwh for our 3.24 kw system would only be $604 per year (3,240 x 4.90 x .7 x .0544). For our last years use of 6,460 kwh that would be 9.3¢ per kwh—much less than PG&E's lowest rate of 13.2¢ for most residential users. It used to be that only people who used more than the base rate would really save money with solar, but now it's everyone in Northern California. Unfortunately, the price of electricity (again, not the true cost of fossil fuels) in other places is still lower than 9.3¢ per kwh so people are holding back. However, when the likelihood of inflation is added to mix—given that the price of solar is fixed for 30 years—the advantage of solar becomes clear.
Now admittedly, PG&E is raising rates for electric vehicle owners--so our price will be a bit higher after 2014, but, with the solar, it would still less than the 13.2¢ that PG&E is charging most people. More analysis of this as the picture becomes clearer.
