In 2014, we installed a 6 kW PV system on a homebuilt rack in our backyard (see HP164). This past April, we purchased a used 2013 Nissan LEAF EV. We’ve put almost 7,500 miles on the car in six months and just love driving it. So now, rather than pumping all that extra PV-generated electricity back onto the electric grid, approximately 280 kWh per month go into the LEAF.

The LEAF replaced an old ICE vehicle, which averaged about 35 mpg. Since we’re making double the price of electricity (present electricity cost = $0.13 per kWh) by using it in the LEAF versus sending it back into the grid, our PV system’s return on investment actually improves! Here’s how I calculate this result (based on five months of our actual LEAF’s efficiency, as well as local average regular gasoline prices):

Equivalent Electricity Cost =
(Cost of Gasoline ÷ ICE Car Fuel Efficiency) × LEAF Efficiency
Equivalent Electricity Cost = ($2.30/gal. ÷ 35 miles/gal.) × 4.1 miles/kWh = $0.27/kWh

The higher gasoline prices go, the faster our PV system pays for itself.

Willi Hampel • via

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