I was at an event recently about Plug-In electric vehicles and the Grid. A representative of my local power company, Georgia Power, was there and mentioned that Georgia Power already has a rate set up for EV owners. I was excited to hear this so I went to Georgia Power's web page on Plug-In Electric Vehicles to learn more. The basic concept of the plug-in rate is that electricity is cheapest when you plug your vehicle in at night after a hard day's work. This benefits the consumer, because demand is lower at night, so electricity prices are lower. This benefits the utility because they get to sell more electricity!
The good news is that plug-in vehicle owners can decide which residential rate plan they want to go with. They can choose to stick with the standard residential rate plan, a nights and weekends rate, or the plug-in electric vehicle rate. If the decision was based on the name alone, most EV owners would obviously go with the plug-in rate...but there may be a catch.
The Georgia Power Plug-In rate plan TOU-PEV-1 lays out the basics of the plan. The rate plan is composed of three different rates as follows:
1) On-Peak : 19.2948 ¢/kWh (yes, they took it out to the 10,000th decimal point)
- June - September, Mon. - Fri.
2) Off-Peak : 5.8295 ¢/kWh
- October - May, all days, 7AM - 11PM
- June - September, Mon. - Fri., 7AM - 2PM & 7PM - 11PM
3) Super Off-Peak : 1.25 ¢/kWh
- All months, All days, 11 PM - 7 AM
The potential catch is that the plug-in rate does not just apply to the electrical circuit that the car is plugged in to; it applies to the whole home! So while users get very cheap electricity during the super off-peak period (at night) when they will be charging their car, their electricity rate during the period when their consumption will be the highest (very hot summer days when AC is running full blast - see our post on How much electricity does my AC consume?) will be very expensive. In other words, while I'm charging my car during Super Off-Peak, I'll be paying about 1/10th my normal price if my standard rate is 10 ¢/kWh. But during On-Peak I'll be paying almost double! So if my total electricity consumption (in kWh) during the On-Peak Period is more than my total electricity consumption in the Off-Peak period, then I may be better off sticking with the standard rate!
For another take on the subject, Purdue University did a study saying that California's tiered electricity rate may hurt plug-in adoption. But their tiered rate is based on different levels of consumption, not different times of usage.
I'm working on a spreadsheet that takes hourly data from my TED 5000 and uses some calculations (if/and/or statements) and an assumed EV battery and applies both GA Power rate structures (the standard and plug-in) to my real-world electricity consumption. I'm probably going to wait until I have actual data from the month of June (when the On-Peak kicks in) to get a better example.
In any case, analyzing rate structures for plug-in vehicles is no easy task! Let's hope the utilities give plug-in adopters the tools necessary to analyze which rate will save them the most money in the long run!