January 2022


To reduce the UK’s carbon footprint the government have passed a law that bans the sale of new fully petrol or diesel cars from 2030 and this has accelerated the demand for alternatives.

Hybrid technology has been around for some time, but the term ‘mild hybrid’ is becoming increasingly popular and there is some confusion around what it actually means. This blog will take you through all you need to know about mild hybrids, and whether you may want to think about buying one for your next car.

The number of hybrid vehicles being sold in the UK is increasing rapidly, and according to the Society of Motor Manufacturers and Traders (SMMT) in 2019 there were 191,000 hybrids sold which was an increase of 52,000 from the year before. Covid put a dent in the rise of car sales in general, but hybrid sales have continued to increase regardless.

Part of the explanation for the increase is because this number also includes other categories of hybrid vehicle: mild hybrids (MHEVs), plug-in electric vehicles (PHEVs), battery-electric vehicles (BEVs) and hybrid-electric vehicles (HEVs).

There was a time where HEVs were the only type of hybrid available. These are vehicles that have an electric motor powered by a battery pack that runs alongside a standard petrol engine. They can’t be plugged in and the battery charges whilst the car is driving which reduces emissions, improves efficiency and registers only a small drop in performance. They can only be driven short distances on electric alone but have still been popular cars especially for inner city environments.

The advent of the plug-in hybrid (PHEV) extended the range of these vehicles and as the name suggests can be plugged into special outlets, but the technology of interest for this article is the mild hybrid

What is a Mild Hybrid?

In a mild hybrid vehicle the regular petrol engine still does all the heavy lifting. It delivers 100% of the power though the drivetrain to the wheels, and so performance is almost identical to a comparable standard vehicle.

The electric motor in mild hybrids instead powers some of the other systems in the car such as the starter motor and alternator which would normally be powered by the engine. Although the car can’t run on electric power alone, the addition of the small motor and battery reduces the load on the engine thus reducing the fuel consumption and CO2 emissions.

The technology is advancing at a rapid rate and the industry predictions are that sales will continue to increase at a steady rate over the next few years. Because the technology is more straight forward than standard PHEVs and BEVs it makes vehicles fitted with mild hybrid assistance far more affordable. Some pundits predict that cars without mild hybrid assistance may become hard to find as we approach the 2030 watershed.

Many manufacturers already have a range of vehicles with this technology as an option in their SUVs, including Audi, Kia, Hyundai, Ford and Fiat. Other marques such as Volkswagen and BMW are starting to add it to their family car range as well.

How does a Mild Hybrid work?

There are a variety of ways that mild hybrid technology can work. On the Suzuki SHVS for example, there is a small generator and batter that can start the car and also provide a bit of a boost to the engine under certain conditions such as hard acceleration.

Most modern cars have an automatic stop/start system as standard, and this is where the starter motor brings it’s value as it can restart your car at the lights much more smoothly.

Other versions of mild hybrid technology have much greater impact on the car’s performance. The latest versions of the Audi A8 and A7 Sportback have a system that has been dubbed the MHEV, incorporates a 48-volt motor which provides enough power to allow the engine to be turned off for up to 40 seconds when the car is coasting. As soon as the accelerator is pressed the regular engine kicks back in and the electric assistance goes back to ticking along and recharging in the background.

There are some useful fuel economy savings to be made here compared with conventional stop-start systems and the cars are proving popular for drivers doing regular longer journeys.

Fuel efficiency is clearly a big attraction and many manufacturers are focusing on these benefits for obvious reasons. However it’s not the only reason why manufacturers are interested in incorporating the mild hybrid technology into their vehicles.

Ferrari has been using the same technology to boost the already-incredible power of it’s hypercar, the La Ferrari, where the system is inspired directly from it’s F1 cars.

As for other types of hybrid models, mild hybrids are eligible for reductions in car tax when compared to standard petrol or diesel and you can expect up to about a 15% difference in fuel economy. That might not sound like much, but with fuel prices at a record high the savings can quickly add up.

Purchasing a mild hybrid is cheaper than a full hybrid model as there are fewer additional components. Mild hybrids have smaller batteries and so they are lighter, and they tend to recharge during braking which isn’t something that all other hybrids can do.

They have higher CO2 emissions compared with full hybrids, and are unable to run on electric power alone.

Mild hybrids are a solid bet at the moment, though expect the price to come down in the coming years as more models are offered with this technology as an option.

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