PHEV vs BEV: Does a hybrid stack up against a fully electric car?

  • #Hybrids
  • Electric cars
  • Mar 23, 2021

Plug-in hybrids (PHEVs) are seen by many as a stepping stone to electric driving. Do the 'best of both worlds' claims really make sense?

Plug-in hybrids are slightly less expensive than a BEV (a full electric car) and there’s less to get your head around in terms of making longer journeys. If you are replacing a petrol or diesel car, the PHEV can sound appealing, but could having one on your driveway be something you come to regret?

We examine the three main selling points of plug-in hybrids to see whether a PHEV really meets these expectations.

Selling point #1: Majority of trips are emission-free

The lure of the plug-in hybrid is this: With a 30-mile battery, PHEV drivers will be able to do their commute on electric power alone Monday to Friday, provided they plug the car in to recharge the batteries, but they’ll still have a car capable of conveniently driving much longer distances at the weekends.

Sounds good, doesn’t it? You can do most of your miles on electric and then switch to petrol for longer trips. The danger is that your average journeys aren’t always covered by the battery - which might have an industry (WLTP) figure of around 30 miles range, but in real-life would do much less than this. Real-world ranges are roughly 80% of the WLTP calculations, so you might get nearer 24 miles electric driving.

With the average UK car trip being between 7 and 9.2 miles, depending on where you live in the UK, the real range is only just about enough to cover an average return trip. Trips over 50 miles may only represent a tiny proportion of all trips, but for an average driver they may account for 25% of your mileage.

Long journeys inevitably mean relying heavily on the car’s petrol or diesel engine – and when you do that, you’re also lugging around a big, heavy battery pack. With the battery depleted, you're likely to achieve around 40mpg with a Mitsubishi Outlander PHEV according to a review by carbuyer.co.uk, but falling further into the 30s if you do motorway driving, according to a review from The Engineer. This might be far less than the car you traded in.

Research by Transport and Environment found that popular models such as the BMW X5, Volvo XC60 and Mitsubishi Outlander emitted three to eight times more than official values on an empty battery. When driven in battery-charging mode (as you might do to charge up ahead of using electric mode in low-emissions zones) the PHEVs emitted up to 12 times more than advertised. If your goal was to do your bit to reduce toxic pollution in our streets, you might unwittingly be doing the opposite.

Mitsubishi Outlander PHEV was 2020's top-selling plug-in hybrid SUV in Europe

The problem is that many plug-in hybrid models include design features that automatically turn on the petrol/diesel engine at start-up on a cold day, or will kick in if the driver accelerates hard. In the Outlander PHEV owners say “If you switch the heating on the engine kicks on automatically, so I tend to use the heated seats instead unless I have the kids with me”.

A PHEVs emissions will depend on the driver's behaviour. But this is not just limited to overzealous acceleration, but includes the uphill climbs on a normal journey and their need to stay warm. This is why, even on a fully charged battery in optimal conditions, the same T&E study found that PHEVs emitted 28-89% more CO2 than advertised.

Another part of the real-world problem of PHEVs is that many plug-in hybrid owners rarely charge their cars, meaning they rely on the petrol or diesel engine on even their shorter trips. It’s partly because past incentives encouraged unengaged drivers to buy PHEVs.  But also because you can't rapid charge, making charging a PHEV more limited.

As you can’t rapid charge, there's a lot more waiting around to recharge the battery if you're using the public network. For the Outlander, DC charging from a rapid unit is available but limited to 22 kW - meaning roughly 1 mile per minute can be added. This compares to the 150kW chargers which are fast becoming the new standard for rapid charging of BEVs.

Without big compromises in waiting time, increasing your electric miles in a PHEV en-route is much more tricky than it is for a BEV. If you match a BEV to your journeys, you'll be able to do most of your charging at home.

PHEV drivers can of course charge at home with a regular socket overnight. A PHEV’s smaller battery can be refilled even from a regular socket in around six hours. PHEVs also qualify you to switch to a cheaper EV tariff. If you can’t easily plug in to an existing external household socket, installing a dedicated home charger is an extra expense. It reduces your charge time to around four hours. This small gain makes a home charger less of a necessity for PHEV drivers than for BEV drivers, who might need it to add two hundreds of miles overnight.

Selling point #2: PHEVs offer the best of both the conventional and electric driving experience

Putting aside the times when your conventional engine might kick in on shorter trips, then yes a PHEV does give you both experiences. The downside is that you have to pay for, and maintain, two powertrain technologies.

A study by Which? found that plug-in hybrids proved least reliable, with 15 per cent of 55,000 drivers surveyed suffered a problem with their car. These were mostly minor faults on relatively new cars, but it highlights that more parts means a greater chance of something going wrong on a PHEV.

As today's PHEVs reach the secondhand market this will inevitably be more of an issue. In contrast, BEVs are much less of a lottery for a secondhand buyer. The health of the battery can be checked using a plugin ‘dongle’ device.

BEV - the pros

  • Longer EV range
  • Lowest running costs
  • Zero-tailpipe emissions
  • Near-silent running
Cons: Charging can add time on longer journeys

PHEV - the pros

  • Normal petrol driving range
  • Reduced running costs
  • Potential for lower CO2 emissions
Cons: Heavy batteries mean less mpg for the petrol miles. Not being able to rapid charge limits the electric miles.

Selling point #3: I’ll be exempt from Congestion Zones in a PHEV

For now, yes. But from October 2021, only pure-electric zero-emission cars will be exempt. London’s Clean Air Zone (CAZ) has just been joined by a scheme in Bath and Birmingham will start later this year. In London, PHEVs will pay £11.50 to enter the London Congestion Charge zone during the week. Even BEVs will have their exemptions removed in December 2025, but that gives BEV drivers over four more years to plan for car-free city trips.

It seems that hybrids, from self-charging to PHEVs, are much more prominently advertised on our screens than full electrics, so it may surprise you that sales of fully electric cars have accelerated faster in the last year and overtaken PHEVs in number in 2021. BEVs are up nearly 55% compared to 28% for PHEVs compared to this time last year.

SMMT data shows that BEVs are growing faster than PHEVs in the last year

A survey by SMMT found the biggest factors holding BEV buyers back are higher purchase prices (52%), lack of local charging points (44%) and fear of being caught short on longer journeys (38%).

Are fully electric cars ready?

The SMMT study back in September 2020 found a third (37%) were optimistic about buying a BEV by 2025, 44% don’t think they’ll be ready by 2035, with 24% saying that they can’t ever see themselves owning one. With better cars, lower price tags and a better charging network, these attitudes are set to change fast.

In the last year, fully electric BEVs have arrived on the market with larger and larger ranges from a single charge. The majority of more affordable BEVs available have a real-world driving range of 150-250 miles from a single charge.

At the same time the public charging network is improving with updated chargers and more locations, meaning your longest journey shouldn’t feel determined by the size of your battery pack. In a great sign of things to come, electric forecourt builder Gridserve has recently come on board and promises to rapidly help the aging Ecotricity motorway network get up to speed.

There’s no denying that with a BEV you will need to plan ahead for longer journeys. Ensuring that a suitable charging location is available or adjusting your routes and time to accommodate a 30-40 minute rapid charge en-route. But, from the perspective of most current EV drivers, the benefits far outweigh the disadvantages. Being able to charge at home overnight when electricity is cheap reduces your cost to as little as 1p per mile. If you can’t home charge but you do commute to work, workplace charging is equally convenient. If you are lucky enough to have a company car allowance, the benefit in kind for electric cars is only 1% for the next two years.

There is no doubt that the car buying process has become even more complex. Electric cars are still unfamiliar technologies, so deciding which would fit your lifestyle and usage patterns, prove most cost effective to run and have most impact on air pollution and carbon emissions is not easy.

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