Let’s start with the Chevy Volt, which has a 16 kWh battery. The EPA site www.fueleconomy.gov/feg/phevsbs.shtml gives the result of their tests as 35.7 kWh/100 miles for city and 37.4 kWh/100 miles for highway. Assuming the full 16 kWh are available, the range would be 16/35.7 x 100 = 45 miles for the city, and similarly, 43 for the highway. However, later in the table they quote “miles on a full charge” as 35 miles. Is it possible that the battery only charges to 80%, or are they choosing special circumstances, such as energy use for air conditioning, etc. ? On the Nissan Leaf, they use the full charge capacity figure for the range. On gas only, the Volt gets a decent 35 mpg city and 40 mpg highway, though not as good as a Prius hybrid.
Let’s jump to the “Annual Fuel Cost” for electric driving only. They evaluate it at a cost of $0.11 per kWh for 15,000 miles average driving. The Volt cost for that usage would be a slim $594 a year. If you use the average of 44 miles on a full charge of 16 kWh, then you need (15,000/44) x 16 kWh = 5,455 kWh a year. At $0.11 per kWh this comes to $600 per year (close to their $594 value).
My point is, however, that the average SC Edison household uses about 6,000 kWh a year. The usage for the Volt almost doubles that. SC Edison charges by tiers, which actually vary by location. Tier 1 is $0.12 per kWh, and the tiers go up to tier 5 which is $0.31 per kWh. Several people I know with families are into tier 5. Even others, when doubling their electricity usage for an electric car, would be into tier 5. So the cost per year that the EPA quotes could really be trippled for many SC Edison users in Orange County. However, if you live in a single unit household, install a separate meter for your electric car, and only charge at certain nighttime off hours, then you will only be charged at $0.12 per hour, very close to the EPA estimated rate.