PG&E E9-A versus EV-A calculator using PG&E downloaded data

PG&E E9-A versus EV-A calculator using PG&E downloaded data

I've banged a quick-and-dirty comparison tool together for folks to allow comparing PG&E's current E9-A rate plan versus the upcoming EV-A rate plan.

The basic concept is you download hourly historical usage data from PG&E (doesn't matter what rate plan you were on at the time, you can download E-1 data and the tool will adjust for you), and then optionally add in extra daily charging hours, and the tool will process your actual historical usage data, add in the theoretical car charging time, apply E9-A and EV-A rates for each time slice, and then give you the total you would have paid under each plan.

I haven't bothered adding -B comparisons, but could do so I guess pretty easily.

I haven't bothered adding anything for people with solar who might be generating during the day to offset usage. Adding this would probably be trickier, because you'd have to know what time of day how much was being generated. That data I guess might be in your PG&E downloaded data but since I don't have solar I have no example to look at. Happy to look at someone's data if they do have net metering to see if I can extract solar generation and use it.

Anyway, for me, it looks like EV will be about 30% cheaper than E9, based on my electric usage from 2008 until just before I got my Model S, and then adding 50 miles per day of car driving to that 2008-2013 baseline:

Total E9: 14815.92 Total EV: 8328.86

In other words, if I use electricity going forward like I used it from 2008-2013, but add in 50 miles per day of electricity, then I can expect that over the next 5 years, I'll pay about $14,815.92 under E9-A, or only $8,328.86 if I switch to EV.

The code is here on Github. To use it right now, you kinda probably need to be a computerish person who knows or can figure out how to install node.js

If you're not, and you don't mind sharing your PG&E usage data with me, send me your XML data downloaded from PG&E and I can run the program for you on my machine and give you the results.

Note it's a bit rough around the edges -- if anyone has any feedback, let me know and I'll try and fold it in.

carlf9121 | 08. Juni 2013


I have the same concern although I am on E7 (Time of Use) which PG&E no longer offers. The Peak-Hours are 12PM~6PM M-F only and other hours, weekends & holidays are Off-Peak Hours. The Peak-Hours are manageable on E7 while on EV9-A Peak & Partial-Peak Hours are very extensive. Unless electricity use is minimal during Peak & Partial-Peak, I can see why EV9-A will not benefit everyone. I'm going to wait until my company installs the charging station and see the effects before I decide whether to adjust my PG&E schedule.

npbruin | 08. September 2013


Thanks for building this easy to use calculator for all of us. I've been trying to build a spreadsheet to do this for months and just couldn't get it right. I've talked with 3 different people at PG&E about staying on E9-A vs EV-A. 2 told me to stay on E9-A and 1 told me to switch. My rough calcs showed clear savings with EV-A. Your calculator shows that my annual bills will drop by 34%! Next stop is solar. I'll give a plug for building that into the calculator in the future. Solar adds some complexity and the solar firms I've spoken with don't have good calculators to deal with the time of use rate structures to spit out an ROI on going solar. On behalf of all of us trying to decipher PG&E's rate options, thank you!

SUN 2 DRV | 08. September 2013

Awesome! So glad I found this calculator. Thanks for all the work you put into it.

I followed your readme instructions and I'm not getting results that match my actual bills, probably because I already have solar installed.

Does your calculator accommodate the net metering values reported by PG&E?

PG&E's interval data reports a single net usage/production kWh value per interval as a positive/negative number. The normal rate applies to both positive and negative values. And in my experience the tiering of rate levels also apply in both the positive and negative directions.

Would you expect the calculator to work OK with Net Metering data (ie both positive and negative Values)?