What is a plug-in hybrid?

Plus, the pros and cons of plug-in hybrid vehicles, otherwise known as PHEVs

Hybrid cars are nothing new. In fact, the first vehicle to combine an internal combustion engine (ICE) with an electric propulsion system dates back to 1899. The rebirth of the technology came in 1997 with the launch of the Toyota Prius in Japan, followed by the Honda Insight in 1999.

For many, hybrids are a good compromise between 100% electric cars and traditional (but polluting) petrol and diesel-powered vehicles. Not only do they have a similar range to ICE cars – so there’s no range anxiety – but they are capable of better economy and are kinder to the planet because they have lower tailpipe emissions.

What are the different types of hybrid cars?

Broadly speaking, there are three types of hybrid vehicle:

Mild hybrid – also known as a MHEV, this is the most basic and common type of hybrid system, utilising a small electric motor and battery to assist a petrol or diesel engine. They harvest power normally lost during deceleration and braking to charge the battery, which has the effect of reducing fuel consumption and emissions and boosting engine performance. In a nutshell, mild hybrid technology allows you to drive as you would in a normal ICE car but with great efficiency, and there’s no plugging-in required.

Full hybrid – otherwise known as an HEV or self-charging hybrid, this is the second most popular type of hybrid on the road and they are similar to MHEVs. A full hybrid also has a conventional engine but is paired with a more powerful electric motor and a slightly larger battery pack. Unlike a mild hybrid, an HEV can often be driven for a mile or two in pure electric mode. Again, the battery is charged during deceleration and braking (known as brake regeneration). Just like a mild hybrid, it is not possible to plug in a HEV to charge the battery.

Plug-in hybrid – the fastest growing type of hybrid has a larger battery that can be fully charged by plugging it in (just like an electric vehicle). It can also be partially boosted via brake regeneration. PHEVs have a limited pure electric range (typically around 30 miles) and once the charge is used up, they effectively run as full hybrids. In theory, some plug-in hybrids are capable of as much as 353mpg with CO2 emissions as low as 18g/km.

Pros and cons of a plug-in hybrid

PHEVs are a great introduction to electrified motoring – a stepping stone between conventional cars and pure electric vehicles. However, like all powertrains, plug-in hybrids aren’t perfect, and they have their advantages and disadvantages:

Pros

  • When they are running in pure electric mode, plug-in hybrids are just like driving an EV, which means they are smooth, quiet, nippy and relaxing – particularly in traffic and around town.
  • In EV mode, plug-in hybrids create no harmful tailpipe emissions, making them ideal for short city journeys.
  • Plug-in hybrids are a good choice for company car users because their tax rating is low. This is because the government rewards users of lower-emission vehicles with a lower benefit-in-kind (BiK) rate which results in a reduced company car tax charge.
  • If you’re using a plug-in hybrid for school runs, modest commutes or shopping trips your fuel bill could drop dramatically because you’ll be running in 100% electric mode and your car will not be using its combustion engine.
  • If you’re looking to run a plug-in hybrid, you will still need to pay vehicle excise duty like with petrol and diesel cars. However, a PHEV qualifies for a reduced road tax (or VED) because lower CO2 emissions mean lower rates.
  • Many EV drivers suffer from range anxiety because they are always worried about where they are going to be able to charge next. After all, the charging infrastructure in the UK is still patchy and there’s no guarantee that there will be a spare or working connection at your chosen stop. A plug-in hybrid simply switches to its combustion engine when the battery is depleted.

Cons

  • PHEVs most efficient when the battery is kept topped up. When the charge has been used up on longer journeys, fuel economy can drop drastically. Depending on the type of car, efficiency could be as low as 30mpg, or no better than a large conventional petrol vehicle because you are effectively transporting an engine and a relatively large battery.
  • Electric vehicles tend to be cheaper to maintain because they have fewer moving parts and there’s less to go wrong. Plug-in hybrids effectively have EV and ICE powertrains, so you still need to budget for the same level of service and maintenance as regular car.
  • Some PHEVs suffer from reduced luggage capacity compared to their ICE siblings because the battery is positioned in the boot. This is now the case with all PHEVs. In fact, some modern plug-in hybrids have more boot space these days because they were designed with under-floor/seat battery storage.
  • The speed at which you can recharge the battery is usually slower than it would be for a fully electric vehicle. Most plug-in hybrids have onboard chargers with low power ratings (3.7-7kW), which means it can take around 2-4 hours to fully charge the battery.
  • Plug-in hybrids tend to cost more upfront (and to lease) than their ICE alternatives. However, this can be saved in the long run because fuel costs are lower on shorter trips, plus the tax benefits.
  • Most new PHEVs come with an eight-year/up to 100,000-mile battery warranty. However, because it’s still a relatively new technology, it remains to be seen how this will impact used car buyers in years to come when the cover has expired.

How popular are plug-in hybrids?

Most of the mainstream car manufacturers offer PHEVs as part of their line-up and plug-in hybrids are now one of the fast-growing sectors, largely thanks to the tax incentives for company car drivers.

In 2023, the UK new car market had its best year since 2019 with more than 1.9 million new cars registered.

Here’s how it panned out when it came to powertrains:

  1. Petrol: 774,484 (40.7% share) – up 13.5%
  2. Mild hybrid: 362,129 (19%) – up 24%
  3. EV: 314,687 (16.5%) – up 17.8%
  4. Full hybrid: 238,942 (12.6%) – up 27.1%
  5. Plug-in hybrid: 141,311 (7.4%) – up 39.3%
  6. Diesel: 71,501 (3.8%) – down 13.8%

So, as you can see, plug-in hybrids were by no means the biggest sector in 2023, but sales were up a massive 39.3% on 2022.

The biggest-selling new plug-in hybrid – by some margin – was the Ford Kuga PHEV. Here’s the rest of the Top 10…

> Revealed: Britain’s best-selling plug-in hybrids

Should you buy a plug-in hybrid car?

The bottom line is that PHEVs are a bridge technology between ICE cars and EVs, and they are a great choice for some drivers, but not all.

If you keep your plug-in hybrid’s batteries topped up, you have a home charger and only make shorter trips, it’s very cheap motoring.

However, if you regularly do longer journeys and/or you can’t charge at home, then you’re probably better off with a mild or full hybrid – or even a conventional petrol or diesel car.

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