PG&E Electric Rates and EVs

Electric Bug

I never knew much about how I paid for electricity. I didn’t know if we had certain hours that were peak or not. So, I called PG&E last week and they explained to me I was on the E1 rate. I told them I had an EV, and they suggested I go to E9 A or E9 B. They are listed here: http://pge.com/tariffs/ERS.SHTML#ERS

Like any good programmer, I decided to do my homework before blindly switching. It turns out that after I did the math, a PG&E representative told me they have a comparison spread sheet on their Plug-In Electric Vehicles page (here’s a direct link to the excel spreadsheet). That page seems to lump a bunch of assumptions together about energy use, but I found that page to be quite accurate in its rough estimates.

First, I wanted to understand the E1 rate. I made a spreadsheet in numbers that included the rates for E1 and E9. They charge a certain amount for a baseline kWh used, and then different amounts based on how much you go over:

Screen shot 2011-04-09 at 8.48.57 AM.png

Currently on days that I charge, I’m using ~1000kWh/day. Yikes…that’s a lot. Our new hot tub also dramatically increased the energy we use.

Based on the E9 rates, I did a quick hack comparison if I was charged that rate for the energy used:

Screen shot 2011-04-09 at 8.51.16 AM.png

Obviously, E9 Peek would be more. But, the key thing is E9 partial peak is lower, and when averaged with E9 off peak my total cost will definitely be lower. Here’s my spreadsheet (using Numbers on the Mac), which includes kWh used over a month. Change the values in the green cells to see updated costs change.

I also downloaded some of my day-to-day energy uses for a weekday and weekend. They include an hour-by-hour of when you used how much energy. I simply dropped the base E9 cost (based on the hour) in to compare it to the base E1 cost they already had listed. I did this on some days when I know I charged at a certain hour; although, I also assume I would move charging to off peak hours to get the best rates. My test showed that I could easily save 15%, and potentially up to 30%. So, all this data tells me to switch.

For the E9 rate, you pay based on the time of use. I made a little chart in numbers to get an idea of what rates occur when (click to download that file):

pgehours.png

That will be handy for knowing when I should do laundry and charge the car. I now need to get an 240v AC relay to turn the car on and off automatically during off peak hours.

Here were a few recommendations from the nice people on the EVDL email list:

http://www.smarthome.com/48781/Intermatic-T101P3-SPST-Pool-Spa-Time-Switch-in-Plastic-Enclosure/p.aspx

http://www.smarthome.com/48760/Intermatic-P1121-Portable-15-Amp-Outdoor-Timer-Heavy-Duty-Outdoor-Timer/p.aspx

http://discountsales.com/shop/module.php?module=show_product&id=1161208837

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Nice, thank you! We have a solar power system and we’re getting a Nissan Leaf this month – we’re currently on E7, but we’ll switch to E9 thanks to your research.

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