Plug-in hybrid electric vehicle (PHEV)

A plug-in hybrid electric vehicle (PHEV) is a type of hybrid vehicle that combines an internal combustion engine with an electric motor and a battery pack. The battery pack is larger than the ones on mild and full hybrids; the battery can be recharged from an external power source, which makes it different from the aforementioned vehicle types.

Compared to all-electric vehicles (EVs), PHEVs have smaller battery capacities since they are designed to operate primarily on their combustion engines, with the electric mode providing supplemental power and assisting in improving fuel efficiency.

Electric Mode

PHEVs can operate in electric-only mode, which is particularly beneficial for shorter trips and city driving. They typically offer a range of 30 to 80 kilometres (20 to 50 miles), depending on the specific vehicle model and real-life driving conditions. When running solely on electric power, PHEVs produce zero tailpipe emissions and offer a quiet and smooth driving experience.

Hybrid Mode

When the charge level in the battery depletes to a predetermined level, depending on the PHEV model, the vehicle switches to hybrid mode, operating like a full hybrid. This means the vehicle’s combustion engine kicks in to provide power along with the electric motor. The transition from electric mode to hybrid mode typically occurs automatically based on battery charge level and driving conditions but also on driver input.

Conserving Battery

Most PHEVs prioritise battery use before switching to hybrid mode and finally relying on the combustion engine. Some PHEVs, however, also offer a “hold” mode. This allows the driver to actively charge the battery while driving using the combustion engine. Alternatively, the driver can conserve battery power for later use in driving conditions where electric power is advantageous.

Charging

The external charging capability extends the electric-only driving range, as the battery can be fully recharged before each trip.

The battery can be recharged overnight even from a common wall socket (Level 1 charger). By using a dedicated Level 2 charging station, it takes the battery around one to two hours to go from empty to 80% full. The exact time depends on the battery capacity and the charging power of the station. For now, the majority of PHEVs available are not compatible with ultra-fast charging Level 3 chargers used by all-electric vehicles (EVs).

Just like MHEVs and FHEVs, PHEVs can make use of regenerative braking, but the larger battery pack needs a charging station or an electrical outlet to be fully charged.

The Benefits

Plug-in hybrids can significantly reduce fuel consumption and tailpipe emissions compared to conventional vehicles. They offer flexibility because they can be charged at a charging station or refuelled like a traditional vehicle at a gas station. But unlike EVs, they do not require specialised charging infrastructure for longer journeys.

However, there is a caveat: the emissions produced during electric-only operation depend on the source of electricity generation. If the electricity comes from renewable sources, the overall emissions can effectively reach zero.

If the electricity used for charging comes from fossil fuel-based power plants, there will still be emissions associated with the electricity generation process. In this case, the overall emissions are similar to or only somewhat lower than those from conventional vehicles.

PHEVs can offer the best of both worlds and serve as a transitional technology towards a more sustainable vehicles, offering the advantages of both electric and conventional cars in a single package.