Energy use for the Leaf is typically 3.5 to 4.0 miles per kWh. So if I drive 12,000 miles annually, that means it consumes 3,000 to 3,429 kWh each year, which is about equal to the wind generator’s output. As such, the PV system’s output—estimated to be about 14,000 kWh annually—covers all other household loads, about 20 kWh/day or 7,300 kWh per year. This leaves some surplus energy (about 6,700 kWh per year) that we could use, perhaps for electric space heating to displace some of the fuel we’re currently burning.
We’ve never done a load analysis in our home, but by adding solar, we’re producing more than our usage—even with charging the EV. Should the grid go down, I probably won’t charge the Leaf until I verify that I have ample energy from the PV and wind systems. I have driven the Leaf 3,491 miles in the 17 months since I bought it, and all of those were within 15 miles of the center of Ithaca. So my driving habits fit very nicely with the Leaf’s specs.
Cost & Motivation
The cost—$127,000—for the wind, PV array, and battery systems seemed reasonable considering the system’s novelty and complexity. The 30% federal tax credit applied to both the wind and PV systems. And a New York State Energy Research and Development Authority (NYSERDA) wind incentive of $11,525 reduced the upfront cost of the wind system. (There is also an NYSERDA incentive for PV systems. However, there were going to be delays in getting the DRI-10 approved for the NYSERDA incentive, so we sacrificed receiving this incentive to expedite the project.)
I’ve been asked how long the payback is, and what effect it has on my monthly bills. I don’t know, because saving money was not my main motive, although I certainly have no objections to it.
“Adding Battery Backup to Your PV System with AC-Coupling” by Justine Sanchez • homepower.com/168.38