What’s the difference between a plug-in hybrid, self-charging hybrid and mild hybrid car?

17 February 2022 Blog

Our guide to untangling the differences between the three types of hybrid cars

If you’re looking for a new set of wheels and you want to move away from a pure petrol or diesel car, then chances are you’ve stumbled upon hybrids. Hybrid cars use batteries and electric motors to propel the car alongside traditional petrol or diesel engines – but what are the differences between plug-in hybrids, regular ‘self-charging’ hybrids and mild hybrids? 

Grab your learning hat and read on – this won’t take too long. And remember to check out our range of nearly new hybrid cars that you can drive away today.

Self-charging hybrids

A self-charging hybrid car (also known as a regular or normal hybrid – like the Toyota Prius above) does not have a charging port, because you can’t plug it in to charge the battery. Instead, the battery is automatically charged as you drive, either by regenerative braking or by the combustion engine acting a bit like a generator. 

Self-charging hybrids have smaller batteries than plug-in hybrids, and as such can’t drive as far on pure electric power. But you don’t have to plug them in and charge them up to get maximum fuel efficiency. The combustion engine kicks in when accelerating hard or sitting at high speeds, and it’ll be used more of the time than in a plug-in hybrid, because a self-charging hybrid has a smaller battery. That said, you’ll always notice the extra punch of the electric motor when you accelerate from a standstill.

The real benefit to a self-charging hybrid is that it fits into your life just like a regular petrol or diesel car – you simply fill it up with petrol or diesel and you never have to bother with charging cables or plugging it in. They’re usually cheaper than plug-in hybrids, too.

Plug-in hybrids

Plug-in hybrids (or PHEVs) have bigger batteries than regular hybrids so can travel further than self-charging hybrids on electric power alone – but you’re still usually looking at about 30-50 miles of electric-only range. 

While PHEVs can charge their batteries from brake regeneration and by using the combustion engine as a generator, the extra battery size means you need to plug them in to charge them up. And once the battery’s empty, the petrol or diesel engine will be doing most of the work, which will see your fuel economy plummet.

If your daily commute is quite short and you can charge overnight at home, then a PHEV makes a lot of sense – because you may rarely have to fill the fuel tank. If you mostly do big trips that quickly drain the battery then you may be better off with a regular petrol or diesel car that doesn’t have to drag around a heavy battery and electric motor.

In terms of driving, PHEVs can usually drive at higher speeds on electric power alone than a regular hybrid, again because there’s more juice in the battery to sustain high speeds without the combustion engine kicking in.

The main downside of PHEVs, however, is the cost – they’re usually the highest spec models, and as such come at a serious premium.



Mild hybrids

Mild hybrids (MHEVs, like the Ford Puma above) are quite different to PHEVs and self-charging hybrids, because they don’t have big electric motors to help propel them down the road. 

A mild hybrid is a petrol or diesel-powered car that uses a small generator instead of a starter motor and alternator, and this is accompanied by a small battery. The generator and battery power a 48-volt electrical system (much more powerful than the normal 12-volt system you find in most cars), and this in turn powers lots of systems that would normally run off the engine – leading to improved fuel efficiency. 

The end result of all this clever technical nonsense is that a mild hybrid feels like a normal car to drive, but is mildly more fuel efficient. And yes, the starter/generator can provide a small amount of extra oomph when you accelerator hard, but it’s not usually that noticeable.

Because mild hybrids are less complicated than PHEVs and self-charging hybrids, they’re usually cheaper – but on the flip side, they’re less economical and often cost more to tax.

We've created a handy list of every nearly new hybrid car for sale at Motorpoint.