Fuel Cost Savings

Just as gasoline prices vary widely depending on location, station, season, fuel grade and other variables, electric rates also span a broad range of prices. The rate options available for charging your EV will depend on your local utility company. Some utilities offer special rate options for charging EVs; others do not and any vehicle power usage is simply added to your existing home electric bill.

Regardless of your electric plan, it is important to understand how it works. Simple plans are based on a flat price per kilowatt hour (kWh), although that price may vary with the season or time of day. Other plans include declining rate blocks, which means the more electricity you use the cheaper it gets – which implies that added usage for EV charging would occur at the cheapest portion of the price spectrum. However, another plan might be based on inclining rate blocks – which means the more electricity you use the costlier it gets. Under this type of plan, additional energy consumption for EV charging would be more expensive.

Before you purchase an EV, be sure to contact your utility company for information on potential discounts and a full electricity cost assessment for the added EV load.

Calculating Charging Costs

Electricity is a very affordable way to power a car that usually less costly than gasoline on a Miles Per Gallon Equivalent (MPGe) basis. Exactly how much money you will save depends on the price of gasoline or diesel where you live and the amount you pay for electricity, which varies from state to state and among utility providers within a state. To find out your electricity costs, visit the U.S. Energy Information Administration web site and search for State Electricity Profiles.

To determine the overall fuel efficiency of a plug-in electric vehicle, you also need to know its miles per kilowatt hour (kWh) rating. The miles per kWh rating is affected by differences in vehicle design, driving conditions, and driver habits.

Here is one way to calculate an EV’s energy costs, based on some typical rates in late 2012. This example compares operating a BEV to a conventional vehicle with an internal combustion engine:

  • If electricity is 10¢ per kWh, and you get 2.8 miles per kWh in your EV, and…
  • Gasoline is $3.259 per gallon for a vehicle that gets 26 miles per gallon…
  • Your monthly energy costs would be $44.64 for electricity, versus $156.88 for gasoline
  • This a 72 percent reduction in energy costs that would add up to an annual savings of $1,344.

Naturally, the calculations becomes more complex when considering a PHEV or EREV whose gasoline engine may be running part of the time. Nonetheless, the more an EV is operated on battery power alone, the greater your savings will be.

The Best Time to Charge

Utility companies want to make the most efficient use of the existing electricity grid by encouraging EV owners to charge their cars at night. It costs utility companies more to generate or buy electricity during the day when demand is high. At night, demand for power declines so utilities frequently offer rates lower during those hours as an incentive to help sell the excess electrical capacity they have available.

Utilities in some regions may also offer special rates to owners of electric cars. Most of those companies will require you to certify that you own a plug-in electric vehicle. Some special rate programs may also require a separate meter to measure the electricity used by your EV. The GoElectricDrive Resource Locator offers information on electricity rates and preferred charging times.