How it Works - Plug-In Hybrid Vehicle

What Is a Plug-In Hybrid (PHEV)?

A plug-in hybrid vehicle (PHEV) is an electrified vehicle with an electric motor (eMotor) and internal combustion engine (ICE) that can operate either independently or together, and a larger capacity battery that allows for a broader full electric mode. Unlike the full hybrid electric vehicle (FHEV), the PHEV can be driven in full EV mode at highway speeds. The electric range of PHEV remains modest (typically between 20-40 miles) but is still significantly larger than that offered by FHEVs. The defining characteristic of PHEVs is that their batteries can be recharged by plugging them into an external power source.

PHEV Batteries and Motor

Like ICE-only vehicles and mild and full hybrids, PHEVs have a conventional vehicle battery in a 12-volt platform to power components like lights and sensors. However, at the heart of the PHEV system is a large battery pack that is bigger than those found in a FHEV, but smaller than those found in a battery electric vehicle (BEV). These batteries are typically between 300- and 400-volts. The eMotor of a PHEV is also typically more powerful than those found in a FHEV.

The Benefits of the PHEV

As the most electrified of the hybrids, PHEVs are designed to have many advantages, including improved fuel efficiency and on-road emissions performance compared to their non-hybrid counterparts. Given the extended range of the PHEV and the ability to “top up” the battery’s electric charge (via braking and/or the ICE), a full tank of fuel can theoretically last a long time if the vehicle is charged regularly. Burning less fuel means fewer CO2 emissions—less than MHEV, FHEV, and ICE vehicles.

The larger battery capacities of PHEVs allow longer distances in EV mode. The guaranteed backup supply of onboard fuel, if the need arises, removes the range anxiety often felt by BEV owners. PHEV owners can take longer trips without worrying about the next charge. When a PHEV is on the road and away from a charger and the battery is depleted, the car behaves like a FHEV and recharges via the ICE and braking. Since ICEs are efficient at high speeds and highway driving, some PHEVs allow the user to apply manual settings to save their charge for city driving, where the ICE is less efficient in slow stop-and-go conditions.

PHEV Outlook

PHEVs can be an efficiency upgrade over FHEVs. They are ideal for consumers who want fuel efficiency and the ability to go farther in full electric mode, but who also want the ICE as a contingency option. However, the fuel efficiency and the extended range come with a higher price. The larger batteries add to the upfront expense, which can be offset over time with fuel savings. While BEVs are almost maintenance free, PHEVs are maintained like an ICE vehicle, with routine services required. Another caveat about the PHEV is that if they are driven like an ICE vehicle, without ever charging the battery, the full potential of the PHEV as a fuel saving strategy will not be met. With all their pros and cons, PHEVs are expected to occupy a relatively small but consistent share of global production over the next decade. During this same period, ICE production is expected to fall as BEV production rises.