What does the acronym 'HEV' stand for?

HEV stands for Hybrid Electric Vehicle.

The term describes a vehicle that combines an internal-combustion engine with one or more electric motors and a rechargeable battery. Unlike a battery-electric vehicle, an HEV does not depend entirely on electricity stored from an external charger; its battery is replenished mainly through regenerative braking and engine-driven generation.

Toyota’s Prius is one of the best-known HEVs. Its Hybrid Synergy Drive coordinates the gasoline engine, electric motor-generators, battery and power-split transaxle. At low speeds and during light acceleration, the electric system can assist or sometimes propel the car, while the engine supplies power when conditions demand it.

HEV is often confused with PHEV, which means Plug-in Hybrid Electric Vehicle. A PHEV has a larger battery and can be charged from an outlet, giving it a meaningful electric-only driving mode. A conventional HEV, by contrast, is designed to recover and reuse energy without requiring plug-in charging.