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# Solar cars and homes and panels. Oh, my!

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Don Ryan / AP / File

(Read caption) Oregon Gov. Ted Kulongoski takes a Nissan all-electric LEAF car for a test drive in Portland, Ore., Aug. 5 with passenger Mark Perry of Nissan North America. The LEAF will go on sale in the U.S. in December. Should LEAF buyers go solar at home, too?

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I will be in Berkeley for only one more day so I'm sitting in a Starbucks thinking about the synergies between buying a solar home and buying an electric vehicle. Let's do some arithmetic together --- concerning the simple economics of green product bundling and the joint purchase of solar panels and an electric vehicle.

In case #1, a solar home owner doesn't own an electric vehicle and she can't sell back "excess power" generation (production - household electricity consumption) back to the grid.

In Case #2, a solar home owner doesn't own an electric vehicle and she can sell back "excess power" generation (production - household electricity consumption) back to the grid at a constant price per kWh.

In Case #3, a solar home owner owns an electric vehicle and she can sell back "excess power" generation (production - household electricity consumption - electricity used by the electric vehicle) back to the grid at a constant price per kWh.

If our goal is to increase residential solar installation then; Case #3 > Case #2 > Case #1. Why?

Consider Case #1: households will only install solar panels if they are big Berkeley greens (the warm glow) or if they are major electricity consumers and located in an area (San Diego) that is sunny and where electricity prices are high.

Case #2: The payoff of selling back power back to the grid is low if the price per kWh is low.

Now consider Case #3: Suppose that an electric car travels 3 miles per kWh. A household who drives 45 miles per day will either need to generate 15 kWh using its solar panels or purchase this extra power per day. If this household owned a vehicle that achieved a MPG of 22.5 and if the price of gasoline is \$3 per gallon, then this household would have spent \$6 per day (roughly \$2,000 a year on gas).

I recognize that a price of \$.1 per kWh, it appers to be cheap to purchase this power from the utility for your PHEV rather than producing the power yourself.