An eGallon is defined as “the cost of driving an EV the same distance a gasoline powered vehicle could travel on one gallon of gasoline.” It was conceived by the U.S. Department of Energy in 2016 as a way for drivers to relate to the cost of electricity more easily. Through some simple math (don’t worry, our tool does all the calculations for you) and a few assumptions, it can translate the cost to charge an EV from dollars per kilowatt-hour ($/kWh) into its dollar per gallon of gas ($/gallon) equivalent.

To calculate an eGallon, multiply together the fuel efficiency of a gas-powered vehicle, the efficiency of an EV, and the cost of electricity.

It is important to understand that eGallon results are based on electricity prices and vehicle efficiency. This means you will get different results when comparing different EVs and gas-powered vehicles. It also means you will get different results depending on where you live because average residential electricity prices vary by state.

To make eGallon costs more accessible, we have setup our calculator to automatically calculate results based on average retail residential electricity prices for each state. We use data from the U.S. Energy Information Administration (EIA), which provides monthly data with a three-month lag. For example, this tool was original created in February 2023, which means the latest electricity rates available at the time were from November 2022.

We also simplified the process by categorizing vehicles according to their class. This helps us ensure we are making fair comparisons between vehicles. For example, eGallon prices will look cheaper when comparing a very efficient EV sedan with a gas-guzzling pick-up truck. We pull vehicle class data from FuelEconomy.gov. We also use FuelEconomy.gov as a data source for vehicle efficiency (miles per gallon for gas-powered vehicles and kWh / mile for EVs).

Note 1: We combined vehicle classes together where it made sense. For example, the compact sedan class in our calculator includes subcompact and mini compact vehicles. Similarly, we group small and standard pickup trucks into a single pickup truck category in our calculator.

Note 2: You may notice that smaller, more efficient EVs have a higher eGallon price than larger, less efficient EVs. For example, compact EV sedans have a higher eGallon price compared to EV pickup trucks. This is because the efficiency improvements gained in switching from an average gas-powered compact sedan to average compact EV sedan are less than switching from an average gas-powered pickup truck to an average EV pickup truck. Compact EV sedans are on average 270% more efficient than gas-powered compact sedans. EV pickup trucks are on average 274% more efficient than gas-powered pickup trucks.

1. Lower Electricity Prices: It makes intuitive sense that if you pay less for electricity then the dollar per gallon gas equivalent price will also be lower.


2. Comparing a More Efficient EV: A more efficient EV can go further on the equivalent of one gallon of gasoline so it will have a lower eGallon cost. Said differently, a more efficient EV requires less energy (and therefore has a lower costs) to drive the same distance a gas-powered vehicle can go on one gallon of gas.
   
   Note that in the eGallon formula, a more efficient EV is represented by a smaller kilowatt-hour per mile (kWh / mile) number. This often causes confusion because we tend to think of vehicle efficiency in terms of miles per gallon with higher miles per gallon being more efficient. Kilowatt-hours per mile simply flips the fuel and distance terms. It may be helpful to think of kilowatt-hours per mile as the EV equivalent of “gallons per mile” instead of “miles per gallon”.  


3. Comparing a Less Efficient Gas-Powered Vehicle: eGallon costs are lower when comparing an EV to a less efficient gas-power vehicle. This makes sense because a gas guzzler can’t go as far on a single gallon of gas. It’s easier for a more efficient EV to cover the same distance using less energy.