Solar Energy Update: Our First Withdrawal From The Bank

Solar Power
ROMT Solar Production (YTD 2017)

As the days got shorter this fall, the amount of power produced by our home solar energy system has been decreasing.

This isn’t surprising – it’s simply a matter of science!

That said, the drop off has been dramatic. Our solar production for November was half of what we produced in October, and less than 30% of what we produced in August, which was our peak month so far.

With the days still getting shorter for another week and a half, science says that our power production for December will be even lower!

Personal FinanceEven though our energy production waned in November, our electric bill still plunged by almost 90% from a year ago.

Unfortunately, this wasn’t all driven by our own energy production during the month.

For the first time since installing our home solar energy system, we had to make a withdrawal from the bank of solar credits we had been building up over the first four and a half months our system was operational.

And it wasn’t a small withdrawal. We generated a little less than half of the energy we actually consumed during November, so we had to use over 25% of the credits we had built up when the days were longer to pay a portion of our electric bill.

Early RetirementThe good news is that we had enough credits to keep our bill as low as possible. We can’t use credits to offset the daily fee to connect to the electric grid and couple of other small fees in our state, so we will always be responsible for paying a small electric bill every month regardless of how much energy we produce.

The bad news is that heading into the winter we now have only $110 in credits to offset the lower energy production we’ll likely experience over the next several months.

We knew heading into our first winter with home solar that our system was sized to produce enough energy to minimize our electric bill over the course of a full year. Given that we didn’t have panels on our roof until late June, we missed out on a few months of potentially strong production during the spring. Because of that, if there’s ever going to be a winter when we won’t have enough credits saved up to offset our usage, this will likely be the one.

We’ll certainly be making large withdrawals in December and January. The big question is how much we’ll have left in the bank heading into February and March, and whether we’ll produce enough power in late winter to avoid running out of credits as we strive to maintain minimal electric bills for the entire year.

We won’t know the answer for several more months, but promise to keep our loyal readers posted!

For readers who already use solar power, how dramatically has your energy production declined during the winter months?

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  • steveark

    December 11, 2017

    Have you compared your annual return on investment with solar versus putting the same amount of money in an index fund portfolio over, say, 10 years? I am curious about what the investment looks like to a homeowner versus traditional investments.

    • ROMT

      December 16, 2017

      Thanks for stopping by Steveark. I know I can often count on you to further the discussion when it comes to solar energy!

      With a payback period of around nine years on our solar panels, putting that money into an index fund instead and earning average historic returns easily beats solar over the first decade. Solar could slowly close the gap in the future years, but when you factor in degradation in panel performance over time, likely depreciation in the residual value of the system, changing rules and regulations, and potential maintenance expenses, it could easily be 20+ years to break even with an index fund. If my assumptions about what I can earn in the stock market are fairly aggressive, I can easily construct scenarios where solar never catches up.

      In my view, solar energy is not an obvious financial decision when you run the real costs involved through a spreadsheet. We still went ahead with the project, in part because our returns on solar over the first decade are more or less guaranteed, while potential returns on the stock market are not. Moreover, when we considered what we were spending on the solar energy system in the context of the 4% rule and our annual electric bill, it was easier to justify as aspiring early retirees. But the true numbers to me are definitely not as clear as they might appear to be on the proposal from the solar contractor!


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