Range test: How far can electric cars go in winter?

Twice a year (in the heat of summer and the chill of winter) we put a selection of electric cars through a ‘drive ’em until they die’ endurance test. The aim? To find out how far they really go on a full charge, and how efficiently they use electricity.

This is essentially our electric vehicle version of a Tough Mudder challenge. After all, temperature can make a big difference to how far an electric car can go on a charge.

We’ve yet to find a model capable of matching its official range – and that was highly unlikely to happen in this latest round of testing, on a very chilly winter's day.

Some of the cars lining up (the BMW i4, Cupra Born and Tesla Model Y) have taken part in previous tests, but there are plenty of newcomers too, including the Genesis GV60 and our reigning Car of the Year, the Volkswagen ID Buzz.

We’ve also included two examples of the Renault Megane E-Tech with different wheel sizes (an entry-level Equilibre and a higher-spec Techno) to find out how that affects their efficiency.

And to see if it’s simply a case of the more money you spend, the farther you’ll get between charges, we’ve included everything from the relatively keenly priced Ora Funky Cat (£31,995), right up to an £85k Jaguar I-Pace.

How we did it

It might seem logical to do our ‘real world’ tests on a public road, but that would present two problems. First, traffic lights, roundabouts and other road users would make it impossible to keep 12 cars together in convoy, throwing a big variable into the mix. Second, there’s the safety side of things. Deliberately running an electric car out of juice on a road could have nasty consequences – not least because you never know exactly when it will stop.

That’s why we always use our test track in Bedfordshire. We follow a relatively simple route of around 15 miles, which includes 2.6 miles of simulated stop-start urban driving, four miles at a steady 50mph and eight miles at a constant 70mph. The rationale for including a high percentage of high-speed cruising is that drivers who want to travel long distances in one hit are likely to be using the motorway network.

The first step was to fully charge up all the test cars, make sure their tyre pressures were correct, then leave them out in the open (unplugged) overnight. They sat for roughly 14 hours in 0 to 2deg C ambient temperatures.

Early in the morning on the day of the test, they were plugged in again to make sure all the batteries were at 100% charge. We put each car in its Eco driving mode (or the closest equivalent), and either left them in the default regenerative braking setting or, if available, the ‘automatic’ or ‘adaptive’ mode.

The cars were then driven around our test route in convoy, with driver changes and a switch in running order after each lap. It was a cloudy day and the temperature ranged from 3 to 6deg C during testing. The cold meant the interior heaters were running continuously.

Controlling the climate

Our original plan was to set the air conditioning or climate control in all 12 cars to 21deg C. However, during preparations the day before testing, we noticed that the MG 4’s interior felt quite a bit chillier than the set temperature.

That was a problem, because electric cars use precious battery power to warm or cool the interior, and if one model was skimping on heat to add distance to the range, it would skew our results. So, to make things as fair as possible, it was important to make sure the interior temperature of each car was the same (regardless of what the air-con displays said).

We invested in a digital thermometer and used the I-Pace as a benchmark, setting its climate control system to 21deg then leaving the doors closed for 20 minutes. During that time we recorded a temperature of 19.5deg at driver chest height – so we set about matching that in the other 11 contenders.

For the record, the Meganes were the only cars with an interior temperature matching the 19.5deg set on the climate systems after 20 minutes. The Funky Cat needed its air-con dialled up to 22deg to get that warm, while the MG 4 had to be set at 23deg.

The winners and losers

With conditions as consistent as possible, we started our laps of the track. As you’d probably expect, the first car to fade and die was the one with the smallest battery: the Mini Electric.

It managed just 113 miles, so a long journey will inevitably involve charging pitstops and probably a lot of range anxiety. More positively, the Mini turned out to be the most efficient car in our line-up, averaging 3.9 miles for each kWh of its battery capacity – impressive considering the temperatures. So, as an urban and suburban runaround, particularly for multi-car households, it makes sense.

The Funky Cat should have a broader appeal. It has more space in the back, costs about the same to buy and officially manages 52 more miles on a full charge. Sadly, in our real-world test, it beat the Mini by only 17 miles and posted the third-worst efficiency figure, 2.9 miles/kWh, which is disappointing for a fairly small car. Its actual range fell 32.8% short of its official WLTP range – the biggest gap in our test.

The next 50 miles went by without any more dropouts, and then the field began to dwindle rapidly. Next to die was the Born at 182 miles, followed swiftly by the two Meganes, at 187 and 189 miles. Surprisingly, the Equilibre on 18in wheels gave up just before the Techno on 20s – the opposite of what we expected. It doesn’t necessarily mean bigger wheels won’t have an impact on range on other models, though.

The ID Buzz dropped out of the running at a respectable 192 miles but was the second most energy-hungry model in the line-up, with an average efficiency of 2.5 miles/kWh. Keeping its vast interior warm probably didn’t help.

The MG 4 stopped four miles later (196 miles), followed shortly afterwards by the I-Pace (197 miles). The I-Pace was the least efficient of the dozen, returning just 2.3 miles/kWh, and unlike the tall and boxy ID Buzz, it doesn’t have a good excuse for its relative inefficiency.

The final four weren’t even breaking sweat at this point and went past 250 miles without further ado. The GV60 died at 251 miles and the i4 gave up the ghost at 261 miles. The Nissan Ariya went into ‘limp’ mode at around 250 miles but carried on for another 19 miles, although the top speed gradually decreased. That helped it to get closest to its official range (it fell 16.4% short).

Even that wasn’t quite enough to beat the mighty Model Y, though. The Long Range version of Britain’s best-selling electric car managed a hugely impressive 272 miles.

Other than the much lighter Mini Electric, it was also the most efficient car in the line-up, averaging 3.6 miles/kWh.

*Based on 34p/kWh charging

How weather affects electric car range

It’s a well-known fact that cold weather is bad for batteries, and the range and efficiency of electric cars plummet in winter. But how big a difference does it actually make?

To answer that question, we need to focus on three of our contenders: the BMW i4, Cupra Born and Tesla Model Y. We compared them all as part of our real-range testing in July, and again in January. The only notable difference was that the i4 we used in the summer had 20in wheels, while the winter test car had 19in ones.

In the cold-weather test, the three models fell an average of 18% short of the distance they achieved in summer, when temperatures ranged from 24 to 29deg C.

The Model Y range fell the least: it ran out of juice 32 miles earlier in winter. The Born’s range fell by 37 miles in the cold, while the i4 gave out 56 miles earlier than in summer.

In other words, if you’re planning a long journey by electric car, it pays to check the weather forecast.

How accurate are efficiency metres in cars

All electric vehicles have built-in meters to help you monitor how efficiently they use electricity. They usually display this in miles per kilowatt hour (kWh) but watt-hours (Wh) per mile is used too.

So – with energy prices on everyone’s minds right now – can we rely on car meters to show which models make the most of a fully charged battery?

Well, our tests show that the answer is... it depends. Some were spot on, while others either over-read or under-read by a fair margin. The Funky Cat promised 15% better efficiency than it was actually delivering, while the Born and GV60 also over-promised by a considerable amount.

The Mini, on the other hand, erred the other way. While its metered 3.7 miles/kWh figure would still have made it the most frugal car here, our calculations show it actually hit 3.9 miles/kWh.

Last year's winter range test results

Summer vs winter last year

**Battery enhancements since summer test, plus winter car was fitted with smaller, ‘aero’ wheels

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