Here are some fundamentals on mandatory PG & E rates (tariffs) if you are charging an electric vehicle. First. PG&E's introductory summary sheet on EV charging rates:
http://www.pge.com/about/environment/pg ... ndex.shtml
Currently you must
switch from your present rate structure (E1 for standard residential, or E6 etc for solar PV) to one of two "experimental" time-of-use rates if you charge an electric vehicle at home. These TOU rates are called E9A and E9B. Here are some things to watch out for:
Tariff E9A charges your EV through your regular home service meter. This means that your EV charging will move your whole house electricity rate up a tier or so (about 300kWh) for every 1000 miles you drive per month. In addition, existing daytime electricity use is substantially penalized in the summer - if you use air conditioning regularly, you'll pay much more per month under tariff E9A even without any EV charging. In general, you'll pay much more for EV charging under E9A than is shown on the PG&E introductory summary sheet.
Tariff E9B charges your EV through a separate service meter, starting over at its own baseline tiering level. Your house can stay on tariff E1, retaining your present electricity rate structure. This can be much more cost-effective than E9A. However, you must have the second meter installed at your own expense, which can range from about $500 to more than $10,000 depending on your existing service entry panel and utility feed. San Francisco does not allow a second meter to be installed.
If you want to ask PG&E for more information, their Clean Air Vehicle Hotline will normally return your call within about 24 hours: (800) 684-4648
EDIT: added San Francisco second meter prohibition