What is a hybrid car? Everything you need to know
Confused about hybrid cars? Here's your complete guide to different hybrid car types, how they work and which could suit your motoring needs best.
- Hybrid car types explained
- Why they don't all need plugging in
- What self-charging really means
What is a hybrid car? Despite them being on the UK's roads for almost 25 years, it's still a question we are asked regularly.
Perhaps that's because the proliferation of choice in recent years and frequently used jargon such as mild, self-charging and plug-in bundled together simply as 'hybrid', it's not readily apparent whether one manufacturer's apples are comparable to another's pears.
Which is why we've put together this guide to undo the knots of bewilderment and explain the different types of hybrid car available so that you can decide which, if any, would suit your needs best.
Hybrid cars now account for 40% of all new car sales with and they are increasing rapidly as more manufacturers ditch diesels in favour of more hybrid models.
So if you want to know what the different kinds of hybrids are, how they work and whether a one is right for you, read our complete guide.
What is a hybrid car?
Let's get the most confusing aspect out of the way first, because 'hybrid car' as a term can mean one of two things.
As an umbrella term it can refer to any car where the petrol or diesel engine is combined with an electric motor and high-voltage battery to benefit overall efficiency and/or performance.
Under that umbrella are mild hybrids, plug-in hybrids and self-charging hybrids — it's the latter of those three which are also referred to simply as hybrid cars, so it's relatively safe to assume that's the type meant if the 'mild' or 'plug-in' prefixes aren't used.
Although self-charging hybrid is becoming more commonly used as a term for these cars, in industryspeak they're Hybrid Electric Vehicles, or HEV for short.
Self-charging came about as a marketing term because these hybrids don't have to be plugged in — all of the battery charging that goes on is because of the engine being used as a generator in addition to harvesting braking energy and converting into electricity.
HEVs combine a conventional engine, mostly petrol but occasionally diesel, with an electric motor and battery system. Usually the battery is small enough to be tucked away under the back seats or boot floor without it compromising interior space.
These systems have the potential to be significantly more fuel efficient than non-hybrid alternatives, with lower CO2 emissions as a result. For the greatest economy, HEVs are best left in Auto mode where the car will decide itself where best to use the electric motor.
Many new self-charging hybrids can also travel for a handful of miles purely on electric power, especially at lower speeds. The longer the engine remains switched off, the less fuel it'll require.
As HEVs don't require plugging in, you simply add fuel to the tank the same way you would a non-hybrid car and to drive they operate entirely conventionally, so no tech overload for newbies.
Popular examples of self-charging hybrids include the Toyota Corolla, the latest Honda Civic and the Hyundai Kona Hybrid.
What is a plug-in hybrid car?
Plug-in Hybrid Electric Vehicles, shortened to PHEV for convenience, are essentially self-charging hybrids with a significant distinction: they can — and should be — plugged in to charge-up the battery pack.
This is because the batteries are much larger and heavier than those found in HEVs, making them very fuel inefficient to charge using the engine alone, something you'll discover on occasions you don't plug them in.
However, use a PHEV's electrical energy intelligently and depending upon the length of your commute, you could see an average fuel economy in excess of 100mpg.
In fact, with many of today's plug-in hybrids capable of travelling in excess of 50 miles on a single charge, for those who typically travel short distances, the sound of the engine springing into life may become something you seldom hear.
We've mentioned that PHEVs' battery packs are larger and this often results in a reduction in boot space to accomodate the additional components. While it's unlikely to render a plug-in hybrid impractical, it's worth seeing the difference in available space first hand before agreeing to buy one.
Company car drivers have latched-on to PHEVs significantly in recent years because their very low CO2 emissions levels translate into small Benefit-in-Kind (BIK) tax bills compared with diesel-only alternatives.
Most manufacturers offer plug-in hybrid cars these days, but some of the more popular ones include the Volvo XC60 Recharge, the Lexus NX and the BMW 330e.
Plug-in hybrids superficially appear similar to range-extender electric vehicles, often shortened to REX or RXEV — both types have engines, electric motors and decently sized batteries.
It's best to think of a PHEV as a hybrid car with a longer electric range, while an RXEV is essentially an electric car with an engine used as an on-board generator, not to propel the vehicle itself.
Range-extenders aren't that common, with only the Mazda MX-30 R-EV on sale currently. Previously, the earlier versions of the BMW i3 were available in RXEV guise, while the Chevrolet Volt and Vauxhall Ampera twins were all range-extenders.
What is a mild hybrid car?
You've probably seen more mild hybrid cars around as most manufacturers are adopting the technology. A Mild Hybrid Electric Vehicle — usually abbreviated to MHEV — uses a small generator along with a tiny lithium-ion battery in place of the normal starter motor and alternator.
This battery powers things that would normally be serviced by the engine, increasing fuel efficiency as a result.
Most mild hybrid cars run on 48 volts rather then the usual 12 volts of a standard petrol or diesel, hence why you will often see 48V next to MHEV when looking for new and used cars.
There is plenty of confusion about the difference between self-charging hybrid and mild hybrid cars, not helped by the car manufacturers themselves. For instance, you can buy a Suzuki Swift Hybrid which even has a 'Hybrid' badge on the boot, yet is actually a mild hybrid rather than a self-charging type.
Other examples of mild hybrid cars include the Fiat 500 Hybrid, the Ford Puma mHEV and the Volkswagen Golf eTSI.
You don't plug in a mild-hybrid car, it simply operates like a normal petrol or diesel car so from behind the wheel you shouldn't notice any difference, apart from hopefully better fuel economy and in some models, better performance.
Mild hybrid cars cannot drive on electric power alone, although the engine may turn off during periods of braking.
Why are hybrids more expensive?
As is often the case with new technology, hybrid vehicles were significantly more expensive in the early days to cover the extra development costs that have gone into making them. The price of batteries and the rare metals that go into them will also drive up the cost.
However, in more recent times, the cost of getting non-hybrid models — diesels especially — through tighter emissions regulations have driven their prices up, too, narrowing the difference significantly.
Are hybrids exempt from ULEZ?
Yes. ULEZ is based on emissions regulations so vehicles that meet Euro6 — introduced in September 2015 for cars and September 2016 for vans — are exempt, as are some models that met the standard earlier. This includes pretty much all hybrid cars, whatever their type.
Since October 2021, hybrids are no longer exempt from the Central London Congestion Charge and only zero-emissions cars — such as electric cars — are free.
However, from December 2025 all vehicles, regardless of fuel type, will have to pay to enter the zone with TfL scrapping the Cleaner Vehicle Discount.
What is the range of a plug-in hybrid?
This question is the automotive equivalent to 'how long is a piece of string?' because there are so many factors that will influence it in the real world.
Although there has been a significant change in the methodology courtesy of the switch to WLTP fuel efficiency tests from the previous NEDC system, officially quoted figures still offer a worthwhile comparison.
When the first Toyota Prius Plug-in Hybrid was introduced in 2012, it had a claimed electrical range of 15.5 miles. The 2024 incarnation, with a larger, better packaged battery, improved aerodynamics and other efficiency boosting tech, sees that figure increase to 47.2 miles.
Combined with their petrol or diesel engines, most PHEVs will be able to cover more than 400 miles before having to stop for refuelling or recharging, but present requirements don't compell manufacturers to publish the overall range figures.
How much does it cost to charge a plug-in hybrid?
How much it costs to charge a PHEV depends on the size of the car's battery, your electricity provider and the tariff you have.
The cost of electricity is usually quoted in terms of kilowatt hours, or kWh. Your electricity bill will tell you how much you usually pay for each kWh. Conveniently, most PHEV battery capacities are also quoted in kWh.
Many electricity providers now offer special EV tariffs with cheaper charging rates at off-peak times and we'd strongy recommend these to any plug-in hybrid owner.
For example, the latest Mercedes A-Class Plug-in Hybrid has a 15.6kWh battery capacity so if you were with OVO using its Charge Anytime tariff, you would pay 7p per kWh, meaning it would cost just £1.09 for a full charge.
On a standard OVO fixed tariff, the unit rate goes up to 22.45p per kWh. The charge then for the A-Class PHEV would be £3.50. Of course you also need to factor in the daily standing charge into these calculations - it's around 67.64p a day with OVO.
Using public chargers, you'll pay different amounts to charge depending on the network. We generally would suggest avoiding public charging points if you have a plug-in hybrid unless it's absolutely essential.
For example, BP Pulse charge different amounts depending on whether you are subscriber, pay as you go customer or are using contactless. But for pay as you go it costs 69p per kWh for a rapid charger. That means it would cost £10.76 to charge the Mercedes.
How do I charge a plug-in hybrid car?
Charging a PHEV can appear complicated at first but in reality it's not much more difficult than plugging-in your mobile phone.
To get the best out of your plug-in hybrid, you'll need to charge it at home. Most PHEVs will come with a cable featuring a three-pin plug at one end, meaning it can be charged from any normal socket. For the Mercedes A-Class mentioned above, this is likely to take three hours and 45 minutes. This isn't very efficient, but it's fine if you're leaving it charging overnight and there's no alternative.
You'd be best having a dedicated wallbox charge unit installed. If you live in a flat (or are a tenant) there's the Electric Vehicle (EV) Chargepoint grant that gives a £350 discount on the cost of buying and installing a home charger.
There was previously a similar scheme for home owners called the Electric Vehicle Homecharge Scheme (EVHS) which ended in April 2022. There is currently no incentive scheme for home owners.
Most home charge units offer charging at a rate of 3.6kW or 7.4kW, but newer PHEVs can also take faster flows of charging. The Mercedes is one such model, capable capable of taking up to 11kW from a domestic supply, meaning a full charge takes just one hour and 15 minutes.
The latest A-Class PHEV is also capable to taking a charge from the faster direct current (DC) public chargers but only at a rate of 22kW. Even so, this reduces the time required to 25 minutes in the Mercedes' case.
