Electric vehicles are made up of three main types: battery electric vehicles (BEV), plug-in hybrid electric vehicles (PHEV), and range-extended EVs (REX).
Battery EVs have no combustion engine, only an on-board battery which provides energy to an electric motor. BEVs are charged from an external electricity supply, typically plugging in to an EV charge point. When required, energy is drawn from the electric-cells and converted to motive power by the use of one or more electric motors.
Plug-in hybrid EVs have an electric powertrain together with a small- to medium-sized combustion engine, which enables operation in full electric mode, using conventional fuel, or a combination of both. Like standard hybrids, the use of a battery enables the combustion engine to be operated at high efficiency. Unlike their conventional counterparts, PHEVs also have an ‘inlet’ socket allowing them to be charged directly from an external electricity supply.
Range-extended EVs are plug-in hybrids with a particular configuration. In their purest form, REXs are ‘series hybrids’ with only electric motors used to drive the wheels. In most respects the vehicle behaves like a BEV, with the battery being charged by an external supply. However, a small internal combustion engine is available as an on-board generator to recharge the battery if required – though this never drives the wheels directly.
Rechargeable batteries are used in all types of EV, the most common types being lithium-ion (Li-Ion) or lithium-polymer (Li-Poly). An on-board battery also enables the use of regenerative braking which tops up the battery during braking, reducing overall energy use by around 20%. In this way, all plug-in vehicles provide high energy efficiency and/or fuel economy and are classed for tax purposes as zero- or ultra-low emission vehicles (ULEVs).
BEV vs PHEV vs REX
The majority of BEVs have a real-world driving range of 100-250 miles on a single charge, depending on the model. As a result, electric cars are well suited for use as private cars and short-range delivery vehicles. Fully electric vehicles are perfect for city driving, commuting, regular delivery routes, and all short- to medium-distance trips which are predictable. Successful use of a BEV typically requires access to a home or workplace recharging unit and, to permit longer journeys, access to the public charging network.
The downside of BEVs is that drivers have to always plan ahead for longer journeys, either ensuring that a suitable charging location is available or adjusting routes and time to accommodate a 30-40 minute en-route rapid charge. While the range limitations of BEVs mean that they are not yet suitable for all journeys, they offer a number of key benefits which, for many EV owners, outweigh the disadvantages, a key benefit being that BEVs can be charged at home or the workplace overnight when electricity is cheap which reduces overall fuel costs by more than 70%.
Both PHEVs and REXs offer longer range and greater fuel flexibility in that they can be charged directly using any suitable source of electricity or can be refuelled using petrol or diesel. Capable of being used as a zero-emission vehicle, these two options are therefore very popular as they offer the best of both the conventional and electric driving experience.
However, with smaller battery backs, PHEVs and REXs are unable to match pure-EVs for electric driving range. They are also often heavier and more complex as two powertrain technologies have to be accommodated. Grants and tax breaks tend to be lower for plug-in hybrids and range-extended EVs, a reflection that they cover fewer miles in zero-emission mode. Furthermore, while most slow and fast public charging points can be used by these EV types, most are unable to utilise the growing network of rapid chargers, meaning that longer journeys are generally driven using the conventional engine.
Longer EV range
Lowest running costs
High equipment levels
PHEV and REX
Long driving range
Reduced running costs
Ultra-low CO2 emissions
Electric drive for short trips
As a special case, range-extended EVs offer longer electric range than most plug-in hybrids, and are fitted with a smaller conventional engine which is designed for occasional back-up rather than everyday use. With fewer models to choose from, the BMW i3 is the most popular REX on the market. However, the latest i3 lineup drops the REX option from the model range.
EV driving experience
Most electric vehicles have excellent acceleration and high torque, especially at lower speeds, and are more than capable of holding their own on the road. Most EVs can easily reach 70 mph on motorways and are required to do so to be eligible for a Plug-in Car or Van Grant. Electric cars can also be high performance vehicles, with acceleration times from the likes of the Tesla Model S P100D as fast as or quicker than even the most powerful hypercars on the market.
In many respects, driving a battery EV is a different experience to using a conventional car. On pressing the accelerator, an EV initially moves in almost total silence, which can be a little disconcerting at first (some BEVs are fitted with noise generators for slow speeds). As the speed picks up, the small amount of ‘engine’ noise that can be heard is quickly masked by wind and tyre noise, which become more noticeable as the speed increases.
The driving performance of plug-in hybrids is very similar to a pure EV or a conventional hybrid, depending on which vehicle ‘mode’ is selected. PHEVs typically offer at least two driving modes: ‘zero-emission’ which forces the vehicle to run on electricity (if charge is available) and ‘eco’ during which the car decides how to most efficiently use conventional and/or electric power. As PHEVs can accept two fuels, they can either be charged directly, or refuelled with petrol or diesel in exactly the same way as conventional vehicles.
With respect to driving experience, range-extended EVs are similar in most respects to BEVs. Typically having a more limited electric range, the on-board engine provides power to extend the range, or a back-up when the battery is depleted. The only limiting factor is the size of the fuel tank which, being the secondary energy source, tends to be small. While REXs provide a close-to-full EV experience with added range security, as BEV ranges increase over time, the likelihood is that REXs will no longer be available as an EV option.