What Is A Plug-in Hybrid?

Rowan Harris 6 minutes Published: 19/10/2021

Plug-in Hybrids (PHEV) are a great first step towards a fully-electrified vehicle. They can cut your emissions, reduce your costs and give you peace of mind on longer journeys. 

The number of Plug-in Hybrids on the road has increased dramatically in recent years. In 2020, plug-in hybrid registrations rose by 91% on the previous year, a testament to their versatility and practicality. 

As we march towards the 2030 ban on the sale of new petrol and diesel cars, the number of PHEVs on the road will only increase. But is a PHEV for you?

What is a plug-in hybrid?

First things first, what is a hybrid car? A hybrid is a car that’s half way between a petrol or diesel and an electric car. That means it has both an engine and a battery that can be used to propel the car. There are several different types of hybrid, namely: mild hybrids (MHEV), full hybrids (HEV) and plug in hybrids (PHEV). 

As the name suggests, a Plug-in hybrid is a hybrid car that can be plugged in to recharge the battery. Other types of hybrid, such as mild and full hybrids do not have this functionality, but recharge using other means such as regenerative braking

The battery pack inside a plug-in hybrid is much larger than in other types of hybrids. This provides greater MPG figures when used in tandem with the petrol or diesel engine, and also means that the car is able to run on purely electric power. 

Running on electric power alone is particularly beneficial when driving in city centres when doing lots of stop-start driving, as the electric motor is more efficient at driving at low speeds and accelerating from standstill.

How does a plug-in hybrid work?

PHEVs will usually start up in an all-electric mode and will run on electricity until their battery pack is depleted. This is typically between 20 to 50 miles, depending on the vehicle. A PHEV will usually switch to purely petrol or diesel when driving at high speeds on the motorway.

A typical example is the Mitsubishi Outlander PHEV, which has three driving modes: ‘EV driving mode’, ‘series hybrid mode’ and ‘parallel hybrid mode’. EV driving mode is the default driving mode, which relies on externally charged battery power to the electric motor. It’s possible to drive 28 miles on this electricity alone. 

Series hybrid mode uses electricity generated by the engine to provide additional driving force when sudden acceleration or travelling uphill is required. When the battery level is low, engine generated electricity is used to enable motor-based driving. 

Parallel hybrid mode is the engine-based driving mode which uses the motor to assist the engine when overtaking cars. It can also recharge the battery. 

As you can see, the range of a PHEV is typically enough to complete short urban journeys using electric only power. 

This means there would be zero tailpipe emissions. At the same time, you wouldn’t have to worry about recharging the batteries on multiple occasions during longer excursions because the internal combustion engine is able to take over when the battery is depleted and also partially recharge the battery itself. 

One thing to bear in mind is that these additional batteries are heavy. While battery assistance usually means that PHEVs can get away with a smaller engine, fuel economy may be less impressive when compared to mild or full hybrids if you decide to drive using petrol or diesel only. 

This means the best way to maximise your savings and reduce your emissions is to keep your PHEV topped up by plugging it in when you get home!

How do I charge a plug-in hybrid car?

When it comes to recharging a PHEV, you have several options. If you have a driveway, it works a lot like electric car charging at home. You can either use a ‘granny cable’ to plug into a UK three-pin plug socket, or you can get a wall charger installed outside your home. 

As you’d expect, the ‘granny cable’ is the slowest option, able to supply just 3kW of power. However, a wallbox will usually be able to provide up to 7.4kW. This should provide a full charge in 2 to 3 hours. 

You may be able to get a faster charge at public charging stations if your PHEV can charge using DC rapid charging. Although this isn’t a common feature, the Mitsubishi Outlander PHEV and Mercedes GLE 350de both allow DC rapid charging at 50kW. Hook up to a public DC rapid charger and you should be ready to drive electric again in less than half an hour. 

Plug-in hybrids also recharge on the go. The engine is able to recharge the battery while driving, and regenerative braking can improve the electric range. 

Regenerative braking can often be used instead of brake pads. When braking in a conventional ICE, kinetic energy is converted to heat energy through friction between the wheels and the brake pads. 

Instead, regenerative braking converts kinetic energy back into electrical energy by disengaging the motor and using it as a generator.

The main benefit of driving a PHEV is that you’ll have lower CO2 emissions and far better fuel economy than a typical internal combustion engine (ICE). 

The advantage of owning a PHEV is most pronounced if you tend to do shorter journeys in urban areas using mostly electric power, with the occasional longer journey. You will need to regularly plug in your vehicle to ensure as much of your driving uses electric range as possible. 

When it comes to driving costs, there are big savings to be made. In August 2021, the price of petrol averaged £1.32 per litre. In an Audi A1 capable of 47mpg, that would amount to 12p per mile. 

If you recharge a PHEV or electric car at the average cost of electricity (17p/kWh) it will work out at around 4-5p/mile.

If you drive around London, you’ll likely be exempt from the Ultra Low Emissions Zone (ULEZ) charge, provided your hybrid meets Euro 4 petrol standards or Euro 6 diesel standards.

Vehicle tax in your first year will either be free or greatly reduced, with a small discount applied in subsequent years. 

If you are purchasing or leasing the vehicle as a company car, you’ll also be eligible for one of the lower BiK tax bands.

Another advantage of driving a PHEV is that you won't ever have to experience the dreaded ‘range anxiety’ associated with EVs. Because there’s also a combustion engine, you can refuel at any petrol station without potentially having to wait for hours while your battery recharges. 

Disadvantages of owning a plug-in hybrid

If you tend to drive longer distances without recharging, the fuel economy on a hybrid vehicle may not be as good as an ICE. Similarly, if you spend more time driving around town, it might be worth spending the extra money on a full electric vehicle, which would go further on a single charge. 

From 25th October 2021, PHEVs will no longer be eligible for the cleaner vehicle discount on the London congestion charge. If you plan to drive regularly within the London congestion charge zone, you may be better off buying or leasing an EV or hydrogen fuel cell vehicle, which will remain exempt until 2025. 

It’s also worth noting that the EVs attract lower BiK tax bands and cheaper road tax.

How much do plug in hybrid cars cost?

Hybrids generally cost more than their internal combustion engine counterparts. Plug-in hybrids are typically the most expensive type of hybrid. 

However, as the price of batteries falls, PHEVs are also becoming cheaper. The Hyundai Ioniq plug-in hybrid is one of the best value PHEVs on the market. 

It’s also worth keeping in mind how much you will save on fuel and tax. However, if you really want to maximise these savings, an electric car may still be the cheaper option. 

Should I buy or lease a plug-in hybrid (PHEV)?

There are some great reasons to buy or lease PHEV. Plug in hybrids offer many of the advantages of an EV without the drawbacks. You can get cheaper fuel, lower emissions and reduced taxes while still being confident that you’ll reach your destination on time.

But EVs aren’t far behind hybrids in terms of price and the range of most EVs is now two or three times what it was a decade ago. Government incentives for hybrid cars aren’t what they once were, so it might be worth considering whether spending a little more on an EV to begin with is the smarter choice.

If you’re uncertain whether a plug-in hybrid is for you, check out our in-depth comparison of plug in hybrid vs hybrid and hybrid vs electric posts.