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Mild hybrid vs traditional hybrid vs plug-in hybrid – which is best?

With so many hybrid systems on the market today, things can get confusing. We round up the three most common

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A variety of hybrid powertrains are currently available

Shopping for your new car used to be as simple as choosing between a petrol or a diesel. But nowadays there are hybrids to consider – and not just hybrids. Series hybrids, plug-in hybrids, range-extending hybrids, parallel hybrids, mild hybrids – it’s all coming up hybrids!

We took three of the most common powertrain options out for a spin to help demonstrate the differences between the three. And these are the contenders…

First, representing the mild hybrid, we have the Kia Sportage 2.0 CRDi 48V. This uses a 2.0-litre diesel engine in conjunction with a 48-volt mild hybrid system to provide a degree of electrification.

Kia's Sportage gives little away to reveal it's a hybrid
(PA)

Next up, the traditional hybrid, represented by the Lexus RX L. Toyota and Lexus are the most prolific hybrid builders on the market – especially Lexus, which took an industry-leading approach to totally phase out diesel in favour of petrol hybrid powertrains. The RX L uses a 3.5-litre V6 petrol engine in combination with an electric motor.

Finally, the plug-in hybrid, represented by the best-selling example on the market – the Mitsubishi Outlander PHEV, which accounts for 50 per cent of the UK’s plug-in hybrid sales. Capable of around 30 miles on electric power alone, the Outlander has a 2.4-litre petrol engine paired to electric motors and a large battery pack with a charging facility.

First, the question of all-electric range. The Outlander is the only car here which qualifies as an ultra-low emissions car, as it’s capable of 30 miles on electric power alone. That should keep it on the right side of forthcoming emissions regulations in big cities such as London, and if you have a short commute it’s possible that you may be able to complete the whole distance on electric power alone.

The popularity of hybrids is increasing every year
(PA)

Plug-in hybrids are the only such vehicles on the market with enough range to be a usable EV, but traditional hybrids are capable of a few miles on electric power alone. The Lexus RX L can run for a couple of miles in stately, silent electric mode, but the battery pack doesn’t have the capacity to keep it up for much longer than that.

Plug-in hybrids are proving popular too
(PA)

In addition, the RX L uses a smaller, less powerful electric motor, meaning performance on electric power alone is limited – head above 37mph and the petrol engine will cut in.

Finally, there’s the Sportage. As with most mild hybrid systems, were it not for the badging you’d be hard pressed to tell there was any electrification at all. There’s no capacity for pure electric driving – the diesel engine remains running at all times, and the electric motor is there more to assist.

The Lexus RX L represents the luxury end of the hybrid segment
(PA)

This factor means the Kia is the most ‘ordinary’ to drive – not necessarily a bad thing, if you’re a traditionalist. With a powerful 2.0-litre diesel engine and automatic gearbox, the combination’s limited to top-spec Sportages, but mild hybrid systems are becoming available on more and more cars – from tiny Suzukis to huge Mercedes.

The Lexus is more of a sacrifice – the gains you make in some areas are reduced in others. For example, the best efficiency gains are to be felt in short journeys around town, where the RX L’s regenerative braking and electric set-off make progress easy and fuel economy impressive. But on the motorway, the electric additions are of little help, and the Lexus isn’t as efficient as the equivalent diesel from other manufacturers.

The Outlander PHEV is one of the most popular hybrids currently on sale
(PA)

If you’re actively looking to electrify your life, you should be opting for the Mitsubishi, or a similar plug-in hybrid. These vehicles are the only ones – short of a full EV – that offer genuine all-electric range, and so should remain on the correct side of future legislation.

Of course, these three vehicles aren’t the only ones on the market – nor are they truly comparable, with prices ranging from under £35,000 to over £60,000. The powertrains, however, represent the three main choices most buyers will face – on top of the usual options of petrol, diesel and pure electric. Choose carefully!

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