What is a mild hybrid electric car (MHEV) and should you buy one?
Mild hybrid is a popular type of fuel technology, but how does it work, and is it different to full hybrids and plug-in hybrids? Here’s everything you need to know…...
You should be familiar with the term ‘hybrid car’ by now. If not, we’d suggest stepping out for a walk to… just about anywhere that’s even remotely built-up. Failing that, a hybrid electric vehicle (HEV) is a car that’s powered by a combination of both a traditional engine and electric motor, which contributes to reduced emissions and improved fuel economy.
The concept went mainstream with the launch of the original Toyota Prius back in 2000, and the continued global development of hybrid technology since then means public interest has risen – considerably.
Data from the Society of Motor Manufacturers and Traders (SMMT) says over 428,000 new hybrid vehicles were registered in the UK in 2024, contributing to a 22% market share. That’s 92,000 more than in 2023.
For further proof that demand isn’t going anywhere, the SMMT’s September 2025 data reported more than 86,100 new HEVs registered. That’s more than the number of battery electric vehicles (BEVs) and diesel cars combined for that month.
In recent years, we’ve seen hybrid cars branch out into further sub-divisions: most notably, plug-in hybrids (PHEVs) and mild hybrids (MHEVs).
PHEVs are hybrid cars that can be plugged in and charged up, both at home and at public charging points, and can be driven on electric-power alone up to a point. Because of this, they are ideal for those who live in the city, and thus, can benefit from the advantages of zero-emission driving on short but frequent journeys.
MHEVs, meanwhile, cannot be manually charged up. Instead, you should think of them as normal cars with a small electric motor fitted to make the engine more economical. Some of the latest models can also drive for very short distances on electric power, but nowhere near as long as a regular hybrid.
In this guide we'll tell you everything there is to know about MHEVs, show you which models are currently on the market, and summarise whether or not you should consider one as your next big purchase. Read on to find out more…
What does mild hybrid car mean?
A mild hybrid is a car that has a small electric generator instead of a traditional starter motor and alternator (the device that keeps the 12-volt battery charged), plus a lithium-ion battery.
Most mild hybrids run on a 48-volt electrical system, which is a higher voltage than the electrical systems found in traditional combustion-engined models. The 48-volt system powers components that would have previously been powered by the engine, enabling the engine to operate more efficiently.
As the sales figures we looked at earlier show, MHEVs are actually more common than you might expect. The technology used is relatively inexpensive to fit, but slightly reduces fuel consumptions and CO2 emissions of both petrol and diesel-engined cars.
It’s also worth noting that it might not be obvious from a model’s name that it’s a mild hybrid. For example, the mild-hybrid Volkswagen Golf is badged the ‘eTSI’, while the Fiat 500 Hybrid and Suzuki Swift Hybrid are MHEVs rather than regular hybrids.
How do mild hybrid cars work?
Mild hybrid cars comprise three key elements: a combustion engine, a small electric motor and a low-voltage battery. This package works in much the same way a traditional combustion engine does, with the difference being that the e-motor kicks in to assist the engine during various small tasks.
This could be during acceleration, or the engine stop/start procedure at a set of lights, with the whole point being to use as minimal amount of fuel as possible to let electricity take more precedence. And while it used to be the case that no MHEV could drive using electric power alone, some of the latest models, such as the Peugeot 308, can drive for very short distances on solely electric power.
MHEVs also use regenerative braking to harvest energy when the brakes are applied or when the car is coasting. That energy is converted into electricity that's fed into a lithium-ion battery and stored until it's needed to provide the extra assistance. On average, a car with mild-hybrid technology can be around 15% more efficient than its conventional counterpart. It may not sound like much, but through mundane daily tasks it really starts to add up.
The current Ford Puma is a classic case in point of how effective a well-built mild hybrid system can be. Most models come with Ford’s 1.0-litre three-cylinder mild hybrid petrol engine – also used in versions of the Kuga and the now-retired Focus. Ford says the system continuously monitors how the car is being driven to determine how intensively to charge the battery and when to snap in and assist the engine.
The system in the Puma can give the engine an extra 15lb ft of torque, so it doesn’t have to work as hard under normal loads, while delivering a 10% improvement in fuel economy. The same boost can be applied when the engine is under heavy load to improve performance, enabling up to 20% faster acceleration.
How much fuel can I save with a mild hybrid?
In most instances, you can expect an improvement of between 10-15% when put up against an equivalent pure-combustion engine. That typically translates to around 3-5mpg, which you’re almost certain to notice over the course of a year.
To put the costs into perspective for you, let’s take the current eighth-generation Volkswagen Golf, which is offered with practically every fuel type currently available. The 1.5-litre Golf TSI with the six-speed manual gearbox has 148bhp, 184lb ft of torque, a 0-62mph time of 8.6secs and offers a projected 52mpg at a CO2 emissions rate of 124g/km. It’ll set you back £30,275 (at the time of writing).
For an extra £1600 you can have the equivalent ‘eTSI’, which has the same engine but gains a 7-speed automatic gearbox and a bit of mild hybrid seasoning. This has identical outputs, but shaves two-tenths off the 0-62mph time, and offers an improved 54.9mpg at a reduced 117g/km in emissions.
The extra 2.9mpg may not seem massive, but considering the difference between the two engines is just £1600, you should expect to break even before long.
What are the most common problems with mild hybrid cars?
The most frequent issues with MHEV engines are the 48-volt battery degrading and troubles with the starter generator. Neither of these are expected to happen when the vehicle is new, but it is something to keep in mind if your car is a few years old. For some perspective, most MHEV batteries are built to last between 80,000 and 100,000 miles.
Are all mild hybrid systems the same?
In short, no. Most mild hybrid systems feature the same components, and tend to offer similar benefits, but the way they work and achieve their efficiency goals can be different. Simply put, some are more clever than others.
The Audi Q8 SUV is a good example of this: the car’s adaptive cruise control system slows it down automatically as you approach corners, which in turn activates the regenerative braking system. It can deactivate the engine and allow the car to coast for up to 40 seconds at a time, saving fuel and lowering greenhouse emissions as a result.
Mild hybrid vs full hybrid: what’s the difference?
Mild hybrids and full hybrids (FHEVs) work in much the same way, using a combination of a petrol or diesel engine with some electrical assistance. The key difference is that full hybrids can drive much further on electric power alone than mild hybrids.
Read more: The best hybrid cars you don't have to plug in
Mild hybrid vs plug-in hybrid: what’s the difference?
Plug-in hybrids (PHEVs) are mostly the same as full hybrid cars, but, as the name suggests, with the added convenience of being able to plug a charger in and regain range as and when necessary. PHEVs tend to trump mild hybrids when it comes to efficiency and running costs, particularly for urban dwellers.
This is because you can complete your various local trips on electric-only power, without needing to activate the combustion engine unless you’re a) on a motorway and doing high speeds, or b) travelling large distances. If you have a cheap, frequent way of recharging your car, you may even find you’ll be doing all your driving off the electric motor alone.
One of our favourite PHEVs is the Lexus NX 450h, which has an official electric range of 45 miles. According to our testers, if you can plug the NX in consistently and mostly stick to short journeys, you could achieve as much as 313mpg. When the batteries have run out, it still has fuel economy of close to 40mpg.
However, if you don’t have access to a reliable home EV charger, or a public charger in close proximity, you’ll end up relying on your combustion engine more frequently, which will work out more expensive. PHEVs also tend to be quite a lot more expensive than non-hybrid or mild hybrid vehicles, so unless you’re actually going to run it on electric power often, the higher cost may not be worth it for you.
Are there any other types of hybrids?
Aside from mild hybrids, full hybrids and plug-in hybrids, there are two lesser-known variants: parallel hybrids and range-extender hybrids. Here’s a quick explainer for you on each:
Parallel hybrids
This is where the hybrid story started, and the fourth-generation Toyota Prius is one of the most widely known examples of a parallel hybrid. They're also sometimes called 'self-charging hybrids'.
The car’s wheels can be powered directly by the engine, by the electric motor alone, or by both power sources working together. When pulling away and at speeds of up to 15mph, it uses only the electric motor for power, making it frugal in city driving. The petrol engine cuts in as speed increases and under hard acceleration.
Whenever you decelerate or use the brakes, the regenerative braking system harvests electricity and stores it in the battery for use later on, but in the Prius, the car can run solely on electricity for up to 1.25 miles. The system is also used in the Toyota Yaris and Toyota Corolla hatchbacks. Models from premium sister brand Lexus also work on the same basis.
Range-extender hybrids
Range-extender hybrids – also known as serial hybrids – differ from regular hybrids in that their combustion engines are there primarily to act as generators, producing electricity to power the electric motors which then drive the wheels.
The Honda Jazz is a popular example. It uses two electric motors, powered by a compact battery, working alongside a frugal 1.5-litre petrol engine. The wheels are almost exclusively driven by the electric motors; the only time the wheels are actually driven by the engine is at higher speeds when it is directly connected to the wheels.
The Honda Civic, Honda CR-V e:HEV and Mazda MX-30 R-EV plus the E-Power versions of the Nissan Qashqai are other examples of range-extender hybrids. According to Nissan, the system gives the Qashqai better performance than you’d get from an equivalent parallel hybrid.
Are mild hybrids cheaper to tax than regular cars?
Mild hybrids aren’t as economical as many full hybrid cars and PHEVs, and they don’t benefit from the lowest rates of company car tax. Until 1 April 2025, mild hybrid road tax rates were also slightly lower than pure petrol or diesel cars, because they were classed as “alternative fuel cars”. This rule has since been abolished, so now, mild hybrids cost the same to tax as conventional petrol or diesel cars.
Are mild hybrid cars more expensive to run and insure than regular cars?
Insurance for a MHEV may sometimes be slightly higher than an equivalent petrol or diesel-engined car. The reason for this is primarily due to the fact that MHEVs contain more expensive parts, like the 48-volt battery, and complex electronic systems. These can lead to increased annual repair costs, which is why insurers may ask for a small premium.
We’d pay more attention to factors like driving record, history and points accumulation, because these are far more likely to determine how much your policy is.
Read more: How to save money on your car insurance
What are the advantages of a mild hybrid car?
- Feels no different to drive than a regular petrol or diesel-powered car
- Fuel economy and CO2 emissions are improved, reducing overall yearly cost
- Sometimes offer superior performance, most often with acceleration
- Contributes to a smoother driving experience, especially since the engine stop/start system is managed more efficiently
- Some MHEVs allow you to coast for longer stretches
- The technology is available with both manual and automatic gearboxes, and across petrol and diesel models
- They don’t need to be plugged in to save fuel, like you do with a PHEV
- Almost always cheaper to buy than a FHEV or PHEV
What are the disadvantages of a mild hybrid car?
- While they produce fewer emissions than a traditional car, they are still not as clean as full hybrids or plug-in hybrids because they are not designed to run on electricity alone
- The limited electric assistance means the fuel efficiency gains are not as substantial as those found in full or plug-in hybrids, which can be a drawback if your main goal is to save on fuel costs
- Mild hybrids typically have a higher purchase price than comparable non-hybrid vehicles
- Their batteries also have a limited lifespan, which means they will need to be replaced at some point at an additional expense
Should you consider buying a mild hybrid car?
Yes, you absolutely should consider a MHEV. For a start, they’re less complex than other hybrids, so in many cases they’re cheaper to buy. They’re also easier to live with than PHEVs, which need to be plugged in regularly to get the best efficiency.
If a PHEV is too expensive or you don’t have access to a charger, a mild hybrid is a cleaner option than a conventional petrol or diesel car. They also work with manual gearboxes, so they’re great for those who want to stick to a more traditional driving experience.
In short, MHEVs tick the most number of boxes with the least amount of drawbacks. So, if you’re convinced, keep reading for a list of some notable MHEVs currently on sale in the UK.
Which mild hybrid cars are available right now?
And for those who are interested in full hybrid technology, here are some examples of cars that can run on electric-only power for short trips, and self-charge without the need for a cable:
- DS 3
- DS No 4
- Lexus ES
- Lexus LM
- Lexus NX
- Lexus RX
- Lexus UX
- MG 3
- MG HS
- MG ZS
How do mild hybrid cars compare to non-mild hybrid cars?
As a follow-up to the above section, we’ve pulled together a list of five MHEVs and their combustion engined counterparts – both in their entry-level guises – for comparison. This should provide you with a clearer understanding of the economical and environmental difference of opting for a mild hybrid.
Citroen C3
- Non-hybrid = Price: £18,805 / Fuel: petrol / Gearbox: manual / Power: 100bhp /0-62mph: 10.6secs / Fuel economy: 50mpg / Emissions: 128g/km
- Hybrid = Price: £20,615 / Fuel: petrol / Gearbox: automatic / Power: 110bhp /0-62mph: 9.8secs / Fuel economy: 56.5mpg / Emissions: 114g/km
CUPRA Leon Hatch
- Non-hybrid = Price: £32,140 / Fuel: petrol / Gearbox: manual / Power: 148bhp /0-62mph: 8.9secs / Fuel economy: 49.1mpg / Emissions: 132g/km
- Hybrid = Price: £33,960 / Fuel: petrol / Gearbox: automatic / Power: 148bhp /0-62mph: 8.7secs / Fuel economy: 53mpg / Emissions: 122g/km
Kia Sportage
- Non-hybrid = Price: £30,885 / Fuel: petrol / Gearbox: manual / Power: 147bhp /0-62mph: 9.7secs / Fuel economy: 39.8mpg / Emissions: 162g/km
- Hybrid = Price: £34,425 / Fuel: petrol / Gearbox: automatic / Power: 235bhp /0-62mph: 7.9secs / Fuel economy: 50.4mpg / Emissions: 127g/km
Peugeot 208
- Non-hybrid = Price: £20,495 / Fuel: petrol / Gearbox: manual / Power: 99bhp /0-62mph: 10.1secs / Fuel economy: 53.5mpg / Emissions: 109g/km
- Hybrid = Price: £26,500 / Fuel: petrol / Gearbox: automatic / Power: 110bhp /0-62mph: 9.8secs / Fuel economy: 65.9mpg / Emissions: 105g/km
Volkswagen Golf Hatch
- Non-hybrid = Price: £30,275 / Fuel: petrol / Gearbox: manual / Power: 148bhp /0-62mph: 8.6secs / Fuel economy: 52mpg / Emissions: 124g/km
- Hybrid = Price: £31,875 / Fuel: petrol / Gearbox: automatic / Power: 148bhp /0-62mph: 8.4secs / Fuel economy: 54.9mpg / Emissions: 117g/km
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FAQs
Mild hybrid versions of cars are generally a bit more expensive than standard models, but you will reap the benefits of the MHEV technology. That means they’ll be more frugal on fuel and have swifter acceleration. If you’re on a tight budget you may want to stick with a non-hybrid petrol model, but if you can stretch to a mild hybrid version it’s likely to be a better choice for these reasons.
Yes, some mild hybrid versions of cars are offered with manual gearboxes. The Fiat 500 comes with a 1.0-litre petrol engine and a manual gearbox, as do a number of Kia models including the Kia Rio small hatchback, Stonic small SUV and Sportage family SUV.
This makes MHEVs different from other types of hybrids, which are only available with automatic gearboxes.
In a sense, yes. Unlike PHEV and pure electric models, which need to be plugged into a power source to top up their batteries, those in mild hybrid models are replenished by the car as it’s driven.
Although there is no set lifespan for a mild hybrid battery, they are designed to last for the life of the car, and that means you can expect a mild hybrid battery to last for at least 80,000 miles. Volvo provides warranty cover for up to 50,000 for the batteries in its mild hybrid models and other brands offer similar levels of cover.
