At the end of year five the meter reading was 98767, meaning we have produced about 1240 KWh more than we consumed over the past 5 years. The first three years we were slightly in the hole, as the meter read 00387, so the gain has come in the last two years. At the end of year four it was 99602 so we came out ahead by 835 KWh this year.
What is surprising about this is that this was our lowest year of production yet, producing a rounding error less than 9 MWh, whereas the first four years we did a little better than 9 MWh. We generated our 46th MWh on March 20.
Is this because the panels are losing their production capacity? Probably a little bit. They are guaranteed not to lose more than 1/2% per year after the first year. However, weather probably plays a factor as well. This past summer we were impacted by smoke from Canadian wildfires. This past February we had two back-to-back snows with freezing temperatures, so the panels produced no power for about 10 days. Just adding what would have been 80 kilowatt hours over that period back into our totals would be enough to get back over the 9 MWh mark.
We had built up enough surplus over the summer and fall that I was sure we would cover the winter deficit. We did cover through January, but the 10 day February shortfall used up the surplus and left us with a small bill (about $22) for that month. Fortunately, we are back in surplus again in March.
As a review, the way our billing works, the March/April bills produce a large surplus (days are longer, sun is higher, no AC) but this gets zeroed out at the end of the April billing period and we get a check in May for the supplier portion of this surplus. The utility keeps the delivery portion.
(Incidentally, the delivery portion has roughly doubled recently, from 2.5 cents to about 5 cents per KWh so electricity now costs about 16 cents per KWh – it was about 10.7 cents early in our journey).
This means we resume building a surplus to carry us through the winter (October – February) starting in May.
I sometimes get asked about the ‘payoff date.’ This is the amount of time until the savings from not paying an electric bill equals the cost of the system. Honestly, I don’t know when that will be as one factor is the current cost of electricity. As that increases, now up about 50% from when we went operational, that date shrinks.
I have rather focused on what the cost of electricity will be for us over the 25 year guaranteed life of the panels. By the way, they keep producing electricity in year 26!
Assuming our panels generate at least 200 MWh over the 25 year period (which seems conservative, as they have generated 46 MWh in the first five years) and assuming the SREC market supports a price of $50/MWh (this is not guaranteed at all – it is currently about $4/SREC in Ohio and over $300 in New Jersey and DC), and that our March/April surplus averages about $60/year, the total cost of the power our panels will generate will have cost us about 2-4 cents per KWh. That is a good deal.
Of course we will have to pay market rates for anything we consume above what the panels generate, but that is to be expected. As of now though, our electricity use continues to decline, as evidenced by the meter continuing to run backward, compared to the same month of the prior year. Should we get an EV sometime in the future, or convert our heat and hot water to electricity this will of course change.
Whether solar panels are a good deal are very much dependent on site location, federal and local $$ help with the project and whether there is something like an SREC market. For this project specifically, it seems to be a great deal.
Here is the comparative overview of the past 5 years on a monthly basis:
