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Adding an Electric Car Cut the Payback Point of Our Solar Panel Investment in Half

A Chevrolet Volt electric car being charged in a parking lot
A Chevrolet Volt electric car being charged in a parking lotPhotograph by Peter Parks/AFP via Getty Images

When we discussed our home solar panel project in mid-2011 with friends, one of the first questions everyone asked was, “What’s the payback period before you break even?” The second question, unsurprisingly, was, “How much is it costing you?” but the focus always ended up on the payback. After all, if you’re going to invest in green technology, you’re hoping that at some point in the near future, you get ahead of the game. It turns out that something we didn’t plan for—our Chevrolet Volt—is actually helping us boost the return on investment and cut our payback time in half.

I shared details on both the solar panel project and the car before, but let me step back and recap a bit. In October 2011, we added 41 solar panels to our southern-facing roof in southeastern Pennsylvania. Each panel is rated for 230W of direct current (DC) so that works out to an array of 9.43kW DC. In our family of four, with two work-at-home adults, we average around 7,500 kWh of electricity usage. So the system may be a bit oversized for our needs—about 125 percent—but we planned ahead. It’s a four-bedroom house so we thought the next occupants could have at least one more family member and therefore use more electricity.