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BMW electric SUV smashes Which? test record with 380-mile range on a single charge

BMW's iX delivers its official range in our tests, while others typically have 18% less range than claimed

After 12 years of testing electric cars, we can reveal the first two models to face our assessments and deliver more than 300 miles on a single charge.

The BMW iX (2021-) and the Mercedes EQS (2021-) have a few things in common - they're desirable luxury electric cars, eye wateringly expensive and capable of travelling more than 300 miles on single charge.

But the BMW iX has an extra trick: It's the only car we've tested since 2017 to deliver its official WLTP range in our tough, independent tests. 

Typically, official range figures that you'll see in car showrooms are not what you’ll get in real life. Our tests have found that the usable range you’ll get from an electric car is typically 18% less than the official figure. In some cases, it's much worse - we've tested electric cars that fall more than 100 miles short of their official range.


Find realistic ranges from our independent tests in all our electric car reviews


BMW iX SUV

Efficiency, not range, is BMW’s true achievement

With the prevalence of cars such as the Nissan Leaf, it can be easy to forget that BMW has been in the electric car game from the beginning.

Releasing the BMW i3 in 2013 (an electric car built from the ground up as opposed to an existing car given an electric drivetrain), BMW is now on the fifth generation of its ‘eDrive’ technology - a drive unit incorporating the electric motor, power electronics and transmission within a single housing. It’s this technology that is, in part, responsible for the BMW iX’s efficiency.

To put its class leading 382 miles of range in perspective, that’s around two weeks’ worth of driving (approximately 350 miles), with a bit to spare. That’s based on the yearly average of 9,000 mileage that consumers tell us they do via our annual car surveys.

Unlike petrol and diesel cars, the fuel economy of electric cars isn't measured in MPG (miles per gallon). The electric equivalent is how many miles you can get per kWh, or mi/kWh. It is also measured as kilowatt hours per 100km, written as ‘kWh/100km’ – in other words, the amount of power your car will use over 100km (or 62 miles).

The average miles per kWh (mi/kWh) for mid/large SUVs is 2.7mi/kWh, meaning on average these massive vehicles get 2.7 miles for kWh used.

The BMW iX has an efficiency of 3mi/kWh. This may not sound like much, but makes it the most efficient electric mid/large SUV we’ve yet tested. Combine that with a massive battery pack and you get 382 miles of range.

To help show this in context, here is a table showing the average efficiency across different car classes, and their average tested ranges. In short, it shows that the BMW iX (2021-) is a 2.5-tonne SUV with the energy efficiency of a medium to large hatchback.

Car classWhich? tested efficiencyWhich? tested range average
BMW iX3 mi/kWh382 miles
Mid/Large SUV2.7 mi/kWh253 miles
Large-sized car*3 mi/kWh229 miles
Compact/Small SUV3.1 mi/kWh195 miles
Medium-sized car*3.1 mi/kWh151 miles
Small-sized car*3.3 mi/kWh153 miles
City car3.5 mi/kWh104 miles

*Typically hatchbacks

Beyond its fifth-generation e-drive technology, BMW uses a number of techniques to maximise its range.

A BMW spokesperson told us that ‘The aluminium spaceframe construction and the Carbon Cage’s use of carbon fibre-reinforced plastic in the roof, sides and rear increases the vehicle’s rigidity at the same time as minimising weight.

‘Air Performance Wheels fitted to the BMW iX reduce the body weight by approximately 15% and improve aerodynamic efficiency. The standard-fit integrated heating and cooling system for the cabin uses high-tech anticipatory thermal management technology, connected to the high-voltage battery and drive system, and makes use of a heat pump to reduce energy consumption during heating/cooling.

‘Each of these innovations together with the energy-dense battery inside the BMW iX, work together to deliver the vehicle’s outstanding range.‘’

However, the flagship electric SUV from a premium brand was never going to be cheap. The xDrive50 version of the iX that we’ve tested, which comes with the larger 104kWh battery, starts at around £107,000. There is a cheaper version, the xDrive40, with a smaller battery and less powerful electric motors, but its starting price is still £77,000.

The Mercedes EQS (2021-) is a luxury saloon with an even bigger battery at 107kWh. But despite being a saloon, it weighs just 100kg less than the BMW’s SUV and is also less efficient, culminating in a smaller (but still impressive) tested range of 360 miles in exactly the same tests. The Mercedes EQS’ WLTP range is in excess of 400 miles.


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Which? car expert Adrian Porter said ‘The BMW iX xDrive50 is a triumph, but a pricey one that’s undoubtedly out of reach for many. But it’s an important car that showcases how electric vehicles are advancing and becoming more efficient.

‘While it’s arguably more important to be able to charge your car conveniently than to travel incredibly far on a single charge, some of the ranges we are starting to see in our independent tests should go some way to putting people’s fears over range anxiety to rest.

‘But alongside developments in electric cars, we need to make sure we have a public charging infrastructure that offers simple, seamless and convenient charging experiences. Especially for those who cannot charge at home.’

Which? is fighting to make EV life as simple and convenient as possible. Find out how we want to shape electric car charging by reading our paper on Building an Electric Vehicle Charging Infrastructure that is Fit for the Future