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Driving in savings-neutral territory so far

The switch to an electric car is a good idea, but it will take awhile before the savings kick in.

May 08, 2010|Susan Carpenter, Los Angeles Times

Ouch. I certainly paid for being an early adopter. And I'm continuing to pay. When I got my latest DWP bill — the first since going solar — I was pleased to discover I was generating almost twice as much electricity as I was using, for which I was credited about $8 per month thanks to an arrangement allowing customers to be credited at retail rates for the power they're making.

At current DWP rates, I'm making 16.7 cents per kilowatt hour during peak periods (10 a.m. to 8 p.m. Monday through Friday, June through September), when the sun is shining and rates are highest. And I'm paying 7.3 cents per kilowatt hour during off-peak, night and early morning hours, when I'm home and using electricity.

I was less pleased to discover that I still had to pay a $10-per-month "minimum charge" that DWP charges "for costs related to meter reading, billing and maintaining service for our solar customers," I was told by a DWP spokeswoman. That fee pretty much wipes out any financial advantage I thought solar would provide.

On the up side, my experience has taught me how others can better navigate the system.

Anyone who wants to charge an electric car using rooftop solar at home should buy the car first. Doing so not only will ensure the maximum rebate from the utility but also make installation more cost effective. According to the folks at 1 Block Off the Grid, it's better to install a large solar system from the get-go than to start small and add on later. Technical and logistical issues may include difficulty finding the same type of panels and a need to change the inverter that transforms solar energy into usable electricity.

I asked how much larger an installation would be needed to accommodate a car such as the Nissan Leaf, presuming a weekday commute of 20 miles. According to 1 Block Off the Grid, the system would need to be .79 kilowatt larger. Applying all applicable rebates, that would cost an additional $1,800. For a homeowner driving the same number of miles in a gasoline-powered vehicle, the system would pay for itself in three years.

Of course, this presumes that the electric car can be charged at home. Although the main reason I chose the BMW Mini E was its existence and availability to me, I also wanted it because the car can be charged with a standard 120-volt outlet, the kind you'd find in any U.S. home, or with a 240-volt charger, like the ones being installed around the nation at public charging stations (most likely to be operated for a fee). One of the points of my e-car experiment was to see how long it takes for one of these cars to charge and what sort of drain it put on a home electric system.

The short answer is a lot. The Mini E takes more than 24 hours to charge fully. It took me 26 hours to charge the battery to 70% of capacity, and it spiked my usage to almost double what my system was making. By comparison, when I took the Mini E to a BMW dealer to have it fast-charged with a 240-volt system, the battery was at 40% capacity in just 90 minutes.

Future electric car buyers, whether they use their existing outlets or upgrade to a 240-volt system at home, should charge their cars during off-peak hours to pay the lowest rate. In L.A., electric vehicle buyers will get a discount, reducing the per-kilowatt-hour rate by 2.5 cents.

I'm still planning to buy an electric car because it's aligned with my values, because I'm using a lot less energy than my system is generating and because there are too many incentives not to do so. Although my experience taught me that I may have been better off waiting, it also taught me that people who want to make the same change shouldn't wait long because the incentives for electric cars and solar panels won't last forever.

My experiment showed me that my rooftop solar will practically make me energy neutral, even with a plug-in car. I paid a lot for solar, but the panels will likely pay me back in spades.

Past installments of Carpenter's column on green home improvement and sustainable living are at latimes.com/realist. Comments: susan.carpenter@latimes.com

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