Plug-in hybrids explained
A plug-in hybrid (PHEV) has a battery you can charge from an outlet and a gas engine as backup. The EPA describes them as hybrids with high-capacity batteries that can be charged by plugging in, able to store enough electricity to significantly reduce petroleum use under typical driving (fueleconomy.gov).
Two fuel costs, one car
A PHEV runs on electricity for its electric range, then on gasoline like a hybrid. So its running cost has two parts, and the split depends on you:
- If you charge every day and your trips are shorter than the electric range, most of your driving can be electric.
- If you rarely plug in, you are driving a heavier hybrid, and the cost moves toward the gas number.
What "utility factor" means
Government ratings need an assumption about how much of the driving is electric. The utility factor is that assumption: the share of driving the rating treats as electric. In our U.S. data, for example, the Hyundai Tucson Plug-in Hybrid has an EPA utility factor of 60%, with an electric range of 32 miles, and a gas rating of 35 MPG after that. The cost per year is then:
utility factor × electric cost + (1 − utility factor) × gas cost
In our tool you can replace the rated share with your own estimate under "Plug-in hybrids: share of driving on electricity". Honest guesses beat the default if you know your commute and whether you can charge at work or home.
In Canada
Natural Resources Canada publishes electric-mode and gas-mode ratings but not the share of driving on electricity. For the Canadian plug-in hybrids in our tool we use the EPA's rated figure for the same model as a starting point and say so on the page.
When a plug-in hybrid makes sense
- You can charge at home or work most days.
- Your typical day is within the electric range, but you also take long trips and want gas as backup.
- You are not ready to rely only on charging stations.
When it does not
- You cannot plug in regularly. You pay for a battery you do not use.
- Your daily driving is far beyond the electric range. A regular hybrid may be cheaper to buy with similar fuel costs.
Read more about home charging before deciding.