What is a plug-in hybrid car?
What is a plug-in hybrid, how can it cut pollution and costs and should you buy one?
The Government has announced that manufacturers won’t be allowed to sell internal combustion engine (ICE) cars running purely on petrol or diesel in the UK from 2030. The ban excludes hybrids and plug-in hybrids (PHEVs), which will remain on sale until 2035 so long as they can travel a 'substantial distance' on electric power alone.
Unlike a standard hybrid car, which is only capable of pure-electric running over short distances, a plug-in hybrid can be driven for a far greater distance on electric power only, typically between 25-40 miles. Plug-in hybrids represent a vital stepping stone between the petrol or diesel cars the vast majority of people drive today and a zero-emissions future. For most owners, the fact plug-in hybrid models can save them money will also help them find favour, with the fact they're also designed to reduce pollution a happy bonus.
Read this guide and you’ll understand not only how a plug-in hybrid car works, but also how choosing to drive one could reduce your motoring bills.
How does a plug-in hybrid work?
You may be aware of popular hybrid models such as the Toyota Prius, Corolla and Yaris, which all combine a petrol engine, a small electric motor and a small battery that assists the engine. This allows for pure-electric running at low speed over very short distances without using any fuel. Plug-in hybrids allow a greater distance to be driven on electricity alone - currently between about 25-50 miles depending on the model.
A plug-in hybrid has a much larger battery, which can be charged via a public charger, a home wallbox or a domestic plug socket. Once fully charged, the journeys you can complete in pure EV mode are much longer, before the fuel-powered engine has to turn on to help power the car.
Like most hybrids, a plug-in hybrid can operate using just electric power, just the conventional engines or a combination of both, providing extra power for times like overtaking or joining a motorway when extra acceleration is required.
Even though a hybrid’s petrol or diesel engine will produce emissions when it is running, the car’s overall emissions are low because the car will defer to electric-only mode whenever possible, at which times it produces no emissions at all. It generally does this at slow speeds, such as in city centres, stop-start traffic and car parks.
For faster speeds the conventional engine takes over, as the power required would drain the battery pack too quickly. It will also take over when battery charge drops below a certain level, even if only driving at slow speeds, and will charge the batteries at the same time until there’s enough electric power available again.
What is a range-extender hybrid?
In many ways a range-extender hybrid is more comparable to an electric car than a hybrid. The best description of a range-extender is an electric car with an on-board power station. You use it in the same way as an electric car, charging it overnight as needed for use the next day. However, you’re not limited to the range dictated by the level of charge in its battery pack. The power station – usually a small petrol engine – is on high alert, ready to charge the battery pack if its charge drops below a certain level.
Although range-extenders are typically classified as hybrids, the following distinction needs to be remembered. All hybrid cars will, at some point, use their conventional engines to provide propulsion, whereas most range-extender cars cannot. One example of a range extender is the now-discontinued BMW i3 Rex – essentially an i3 electric car fitted with an auxiliary engine under the rear boot floor to provide electricity, increasing its range beyond the limits of its battery. While vehicles of this type typically use electricity alone to operate, the small fuel tank will need filling up from time to time as a backup.
You can read more about range-extender cars in our separate guide.
Plug-in hybrid running costs
Company-car users in particular would be wise to consider a plug-in hybrid for their next car, and the reason for that is down to the way carbon dioxide (CO2) emissions are measured.
As you may know, company-car tax, or Benefit-in-Kind (BiK), is levied according to a car’s CO2 emissions. The lower these emissions, the lower its tax liability. We go into greater depth in our feature that explains what fuel economy figures mean to you, but the upshot is that plug-in hybrid cars tend to do extremely well in fuel-consumption tests.
This is purely because a plug-in hybrid can be expected to run in electric mode for much of the official test cycle, and when using the power in its batteries, it produces no CO2 at all. This means that plug-in hybrid cars frequently emit under 50 grams per kilometre (g/km) of CO2 in official tests, which is the upper limit of the lowest Benefit-in-Kind bracket of 10%.
The importance of this to company-car buyers can’t be overstated. Put simply, a car in the 9% BiK bracket will potentially cost half as much in company-car tax as one in the 19% bracket.
Of course, BiK is based on the taxable (P11D) value of a given car. And, while it’s true that a plug-in hybrid usually costs more to buy than a petrol or diesel model, most will cost you substantially less in annual company-car tax than a purely petrol or diesel-powered equivalent.
If you’re not a company-car driver, you could still be quids in if your usual daily drive largely consists of low-speed, urban motoring. Crowded city streets are where plug-in hybrid cars really come into their own – if your daily commute is made up of stop-start driving and totals less than 30 miles or so, you may be able to make the journey without using the petrol engine at all. This means you can rely on cheap electricity, rather than pricey petrol or diesel.
However, if you regularly do higher speeds and longer journeys, the more the petrol engine in a hybrid will be called upon. A long motorway journey in a plug-in hybrid may use more fuel than the same trip in a modern diesel car.
In conclusion, a plug-in hybrid’s ability to save you money is skewed heavily in favour of company-car users, but urban-living low-mileage private buyers may well see the benefits as well.
Disadvantages of plug-in hybrid cars
While regular hybrid cars tend to be more expensive to buy than their petrol-powered equivalents, the same is even more true of plug-in hybrids. Much of the increased cost is due to a more powerful, higher-capacity or more advanced battery than those used in regular hybrids. There’s also extra equipment required for charging directly from the mains and there may be higher manufacturing costs to produce the car in the first place. In short, the added technology and complexity of a plug-in hybrid will usually make it more expensive to buy than a normal hybrid.
It’s worth remembering, though, that you’ll need access to a mains supply or fast charger close to where you regularly park in order to charge your plug-in hybrid. Although the national electric car charging infrastructure is rapidly expanding, you may find overnight or daytime charging tricky to achieve if you find it difficult to park outside your house or office for more than a couple of hours
Plug-in hybrids: range
Just how far a plug-in hybrid car can travel – known as its range – in electric-vehicle (EV) mode alone varies from car to car. However, with the option to fully charge the battery from a mains supply before you embark on your journey, you’ll be able to drive further than in a regular hybrid before the battery needs topping up, either from the engine cutting in or when you next plug it into a mains supply.
For example, the plug-in BMW 330e has a range of around 30 miles in all-electric mode. This is enough to cover many drivers’ morning commute, with the petrol engine boosting the battery in higher-speed parts of the journey and electric power alone in stop-start traffic. It’s in these situations – traffic jams, or generally congested areas – where low emissions are particularly valued.
The difference between a regular hybrid car and a plug-in hybrid is highlighted when you look at the Toyota Prius. The normal Prius hybrid’s all-electric range is only 0.6 miles. This doesn’t sound like a lot but, if the Prius spends most of its life making low-speed urban journeys in heavy traffic – which is what its designers intended – its electric motor may be operating as much as 70% of the time.
With the Toyota Prius Plug-In, reliance on the petrol engine is reduced still further. With the facility to fully charge the battery pack from the mains, the Prius Plug-In has a longer claimed all-electric range of 31 miles if the batteries are fully charged, with a full charge taking two hours. This longer range enables more of each journey to be made without help from the petrol engine, further reducing average CO2 emissions.
Plug-in hybrids: battery life
As with electric vehicles, a common fear when it comes to hybrids is battery life. As anybody with a mobile phone or a laptop computer knows, battery performance can degrade over time. The warranty for hybrid cars may specifically allow for this. For instance, Kia outlines its expectations for the battery life of its plug-in hybrid model range within the careful wording of its policy: "The Lithium-Ion Polymer Battery warranty covers a minimum capacity for a period of 84 months or 100,000 miles from the date of first registration, whichever comes first. This warranty covers repairs needed to return the battery capacity to at least 70% (65% for cars shipped after 01 August 2019) of the original battery capacity. Where possible, the original EV battery components will be repaired and will be".
It’s worth remembering, though, that hybrids’ battery packs are specifically designed to survive any demands that could be reasonably expected from the vehicle. Toyota, for example, states that its hybrid and plug-in hybrid battery packs are intended to last the lifetime of the car. The standard battery warranty covers five years or 100,000 miles, with Toyota also offering Hybrid Battery Extended Cover, which adds an extra year or 10,000 miles of coverage. This can be renewed up until the car is 15 years old, with no restriction on the total mileage.
For its older hybrid models, Toyota also has a clause in its warranty that specifically states the cover provided for a battery pack, with the duration of warranty cover depending on when the car was built. For example, cars registered between 1 June 2010 and 31 March 2014 enjoy an eight-year/100,000-mile warranty specifically for their battery packs. It’s therefore worth checking with your dealer exactly what the battery warranty period will be for your particular car.
What plug-in hybrid cars are there to choose from?
Most manufacturers now offer electric or hybrid versions of at least one car in their range, and many are now introducing plug-in technology too.
For example, the pioneering Toyota Prius hybrid is also available as a plug-in hybrid boasting a longer all-electric range and lower emissions than the regular hybrid model. Toyota also offers standard hybrid variants of its popular Yaris and Corolla ranges, and the RAV4 SUV is available as both a hybrid and as a plug-in hybrid.
While the Mitsubishi Outlander PHEV was one of the very first plug-in hybrid SUVs, it now has a long list of rivals including the Kia Niro plug-in, Ford Kuga PHEV, MINI Countryman, Peugeot 3008 Hybrid and the Citroen C5 Aircross Hybrid.
Volvo has given its electric and plug-in hybrid models the ‘Recharge’ name. This range consists of PHEV versions of the XC90, XC60 and XC40 SUVs, the S90 and S60 saloons, and the V90 and V60 estate models.
Audi offers e-tron plug-in hybrid variants of its A6, A7 and A8 models and across its SUV range, including the Q5, Q7 and Q8. Volkswagen has plug-in hybrid GTE versions of its Golf and Passat models, both of which share the practicality, comfort and styling of the cars they’re based on. It’s worth bearing in mind that they both have slightly less boot capacity than their conventionally powered equivalents, because the batteries for the electric motor take up some of the luggage space.
The same is true of the Mercedes A-Class A 250 e, the Mercedes E 300 e and E300 de hybrid models and the Mercedes GLE 350 e SUV, which, luggage space restrictions aside, are extremely similar to the regular versions of their model lines
The BMW 330e is a plug-in hybrid version of the successful BMW 3 Series compact executive saloon. With average emissions stated as below 50g/km and claimed fuel economy of over 200mpg, it’s available alongside a pair of 5 Series hybrids called the 530e and 545e. BMW also offers the X5 as a PHEV; the xDrive45e model promises over 50 miles of electric range.
Plug-in hybrid government grants
In 2018, changes to the plug-in car grant meant that the £2,500 available for plug-in hybrid models was axed. As of 2020, the plug-in car grant (PiCG) is now only available for buyers of zero-emission electric vehicles with a price of under £50,000, including optional extras.
While the PiCG deduction no longer applies to plug-in hybrid cars, owners of eligible vehicles can claim a subsidy of up to 75% of the cost of buying and installing a home charging point, up to a maximum of £350. This subsidy is offered as part of the Electric Vehicle Homecharge Scheme (EVHS), which is a Government-backed initiative to encourage drivers to switch to low or zero-emissions vehicles.
To qualify for this scheme, you must fulfil the following criteria: You must own one of the eligible cars for the subsidy from the current list here.
- Only the primary owner of a car is eligible for an installation at their home address:
- Owners must be able to prove ownership of an eligible car, or that an order has been placed for an eligible model for delivery within four months of the installation date of a charger.
- For households that own two eligible cars, a second grant can be applied to another chargepoint.