Proposed change to PG&E E9 Time-of-Use Plan

I’ve had the Volt for about a month now, and my electron-fueled travels have been perfectly fantastic. As of this afternoon, I have driven 1,002.7 miles and consumed 1.1 gallons of gas. Still, I can not yet answer the question that I get most often: “What about your electric bill?”

At the beginning of the month, I changed my service plan from the standard issue PG&E E1 residential rate plan to E-9A, a “time-of-use” plan designed for customers who charge electric vehicles at home. With this plan, rates are higher during peak times, and lower at off-peak times, thus providing a good incentive to charge up the car at night when demand on the grid is low, and there is plenty of generation capacity with electrons to spare. Complicated as this is, the Volt allows me to program in all of the rate details, and it figures out when to charge itself.

Until this month, I was able to use PG&E’s website to download daily and hourly demand history from my SmartMeter. Now that I’ve switched to a plan where this hourly usage data actually matters, it is no longer available. Thanks PG&E! So I will not know the true costs for this plan until I get the first bill in a few weeks.

Just the other day, a forum post at gm-volt.com caught my eye: Major change in PG&E CA E9 TOU rates. It seems that PG&E proposed some “helpful” changes to the E9 plan on September 26, 2011. In Advice Letter 3910-E, they propose a new rate schedule. According to this letter, the changes will cause an overall increase in payments for 3/4 of the customers on the E9A plan. Since I had gone to the considerable trouble of Decoding TOU Rate Plans not long ago, I decided that it was time to dust off my spreadsheet and calculate the impact of the proposed change for my expected usage.

The perplexing result of this effort confirmed the same surprising conclusions of some other PG&E EV customers: the new E9 plan is substantially worse than the old E9 plan, and is actually the same or better than the standard E1 plan. The results of one year of simulated use is depicted in the figure below.

PG&E’s proposed change makes the E9 plan useless: EV owner will have no reason to choose a time-of-use plan, and will have no economic incentive to charge at off-peak times. This change seems to be completely counter to the public interest, and to PG&E’s own best interest. Go figure.

Here’s a link to my spreadsheet for calculating simulated annual billing under various confusing and convoluted rate plans. I think it’s reasonably accurate, but who knows. If you find it useful, or can make any improvements, please drop a comment here.

TOU_Simulator.xlsx

UPDATE (10/9/11) The Numbers Are In!

The first PG&E bill has been posted, and it is quite a whopper! Electric costs are $219 for 896 kWh compared with $122 for 683 kWh in the same period last year: An increased cost of 80%, for 31% more electrons. That’s the magic of tiered rate plans: the more you use, the higher the incremental cost. As it turns out, this billing period is historically the highest of the year for us, and this year, there were more hot days than usual – so lots of A/C during expensive peak hours. I estimate that the car should account for no more than 7 kWh/day on average, but our total usage was nearly 8.5 kWh/day higher this year. Unfortunately, it is nearly impossible to unravel the cost impact for the extra A/C from that for the Volt. So rolling everything together, in the first month, the cost of additional electricity (plus 1.1 gallons of gas) works out to 11.64 cents/mile, or a modest 31% savings relative to my old 24 MPG car. I’ll update the stats monthly, or until I get bored. Here’s a link to my Google Spreadsheet:

Volt Dollars per Mile