The tests by Autocar's sibling titles were conducted with four identically specced cars driven to a specified route and within defined parameters for driving style at a proving ground last summer and again earlier this month to discover how lower temperatures affect electric car battery efficiency.
In the winter range test, the Porsche Taycan 4S Performance Battery Plus managed 224 miles on a full charge. That’s a 20.1% drop on the 281 miles that the same model on the same-sized wheels achieved when What Car? tested it last summer.
Significantly, the test also revealed the positive impact of buying an electric car fitted with a heat pump, which reduces strain on the battery by drawing excess heat from the electric drivetrain, distributing it around the interior of the car through the air conditioning.
Five models equipped with a heat pump were tested and they fell short of their official WLTP mileage figures by an average of 25.4%. By comparison, five models that relied on a regular interior heater suffered an average deficit of 33.6%.
The tests were conducted on a closed vehicle proving ground, on a 15-mile route consisting of 2.6 miles of simulated stop-start urban traffic, four miles of steady 50mph driving and eight miles driving at a constant speed of 70mph to simulate motorway journeys.
Winter vs summer range test results
Porsche Taycan 4S Performance Battery Plus
Battery size: 83.7kWh; Summer range: 281 miles; Winter range: 224 miles; Difference: 20.10%.
Ford Mustang Mach-E Extended Range RWD
Battery size: 88.0kWh; Summer range: 302 miles; Winter range: 247 miles; Difference: 18.00%.
Skoda Enyaq iV 60
Battery size: 58.0kWh; Summer range: 207 miles; Winter range: 174 miles; Difference: 15.70%.
Fiat 500 42kWh Icon: Battery size: 37.3kWh; Summer range: 140 miles; Winter range: 118 miles; Difference: 15.20%.
Cars tested during winter range test