Plug-in hybrid electric vehicles (PHEVs) can save fuel by using electricity from the grid to power the car. To figure out how far a PHEV can go on electricity alone, researchers compared its fuel efficiency in electric mode to a regular hybrid car. PHEVs aim to use as little fuel as possible for each trip. They mainly have a motor and a battery, with the battery size determining how far the PHEV can run on electricity. A PHEV's battery size is similar to that of an extended-range electric car. The idea of vehicle-to-grid (V2G) is that PHEV batteries can also send power back to the grid. So, PHEVs can be energy sources too.