Saturday, December 11, 2010

PG&E and Electric Car Chargers

If you recall, we applied to PG&E for a 200 amp service upgrade at the beginning of November (we currently have 100 amps). The request has been grinding its way through PG&E's process. A few weeks ago, we informed them that we would be getting an electric car next year. This week, The Lovely Wife got a call from a Glenn, from PG&E. He asked to speak with me. Because he called TLW on her cellphone, I wasn't there. But he never called me back. On Thurs. at our weekly project meeting, Paul told me that he had spoken with Glenn (I guess he thought Paul was me) and what PG&E wanted. What they wanted was to know whether we wanted a second meter for the electric car.

I was puzzled. Why would we want a second meter? Paul said that PG&E wanted us to charge the car at night, to avoid overloading their transformer and the circuits that supply our neighborhood. The claim is that an electric car establishes a load equivalent to another house. The charger draws maximum 40 amps at 240V (but most likely less than that, since breakers are typically overprovisioned). That's 4.8 kw, a pretty hefty sum, and that over 6 hours, for a total of 28.8 kwh. If I'm the only person in the neighborhood charging, then there is probably no problem. But if electric cars catch on, PG&E is in trouble. They will quickly run out of overprovisioned capacity and need to start upgrading their transformers and other "last mile" circuits. As we know from the telcom world, utilities hate to upgrade "last mile" infrastructure because there is a lot of it and therefore upgrading is expensive.

I don't think PG&E has much to worry about, personally. I suspect my neighbors with houses built in the 70's like mine (some were built later) all have a 100 amp mains feed like ours does. In our neighborhood, the mains feeds are underground rather than coming from  a pole, which makes the neighborhood look nicer but makes upgrading a real challenge. Rather than simply restringing a wire, PG&E needs to bring in a backhoe, dig up the conduit, and replace the 100 amp line with one that will handle 200 amps. Backhoe work is expensive and PG&E's process is time consuming. I can't see any of my neighbors going through that kind of grief, unless gas gets up to $6.00 a gallon. Then maybe even the two neighbors across the street with two SUVs each might have second throughts.

Anyway, I pondered briefly if we did want a second meter for the electric car charger. PG&E offers a special tariff for electric car charging service, called E-9. The cost works out to around $0.06/kwh at night and $0.30/kwh during the day. So there is a real financial incentive not to charge during the day when more power is being used by businesses and residences. But we are already on a time of use tariff,  E-7W, for our solar PV. This has the same kind of incentive: $0.09/kwh at night most of the year and $0.30/kwh during the afternoon in summer (the winter rates are much less). The rate on summer afternoons is high because PG&E needs the power for all the air conditioners in the Central Valley. We can save big time by not using power then and banking the credits for the winter, when our solar panels get little sun and the folks in the Central Valley have their gas heaters cranked up instead of their air conditioners.

But the $0.03/kwh differential in price caused me to haul out my calculator. Would we save by taking a second meter an the E-9 rate? Our new solar PV system has 2000 kwh/year capacity designed in for the Nissan Leaf. This amounts to around 8000 mi/yr, the amount we usually drive our around town car, at 0.25 kwh/mi, the amount of energy a reasonably aerodynamically efficient electric car uses. Since we cannot connect up the solar PV system to more than one meter, the generated power would not offset the power we use for the electric car on the second meter. Instead, PG&E would reimburse us for it, which they will start doing next year. The rate we get is paltry, $0.08/kwh, even for the expensive power we generate in summer (this is a ripoff in my opinion, but that's the subject of another post).

We would end up paying $120/yr for power on the E-9 rate and getting back $160/yr for the solar power we sell to PG&E on the main meter, for a grand total of $40 to our credit, enough for a nice lunch for two at a fancy Palo Alto restaurant. Looks good, right? Think again! PG&E also charges you $75/yr for renting the meter. So we would end up paying $35 more with a second meter than with a single meter. And, in addition, we would be constrained to always having to charge at night, even if we occasionally need to charge in the afternoon on a weekend because we have taken the car somewhere (this happens sometimes with our current plug-in hybrid). So our answer to PG&E is a polite: "Thanks but no thanks."

According to PG&E's online schedule, the 200 amp upgrade begins Dec. 24. Think of that: PG&E as Santa Claus!

3 comments:

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