Summary of key findings
Most UK EV owners report summer efficiency of approximately 3.5–5.0 mi/kWh in mixed driving conditions, with some outliers. This range encompasses vehicles from heavy SUVs on motorways to light hatchbacks on urban roads. In winter, efficiency typically decreases by 15 to 30 per cent, depending on vehicle type and heating system.
These figures are based on real-world data collected from trip computers, mobile applications, and manual calculations by UK drivers. We matched over 30 individual reports from a UK EV community on Reddit to our catalogue for comparison. The complete dataset is available on the model versus owner efficiency data page.
Seasonal variation: summer versus winter efficiency
Winter efficiency declines due to two primary physical factors. First, colder air is denser; at 2 degrees Celsius, air density is approximately 5% higher than at 20 degrees, increasing aerodynamic drag at all speeds. Second, the cabin heater draws power from the battery. A standard resistive PTC heater can consume 2 to 4 kW during severe cold, directly reducing driving range.
Owners generally report a 15 to 25 percent reduction in efficiency during winter. The precise value depends on ambient temperature, journey length, and the presence of a heat pump. Short trips in cold conditions are most affected, as the heater operates at maximum output for a greater proportion of the journey.
Impact of heat pumps on efficiency
A heat pump transfers heat from the outside air into the cabin, rather than generating heat directly. Above approximately minus five degrees Celsius, a heat pump provides equivalent heating for about half the electrical consumption of a PTC heater. Below this temperature, the efficiency advantage diminishes, and the heat pump’s performance approaches that of a resistive heater.
This trend is evident in the owner data. Vehicles equipped with heat pumps, such as the Hyundai Kona Electric and BMW i3, exhibit smaller reductions in winter efficiency compared to similarly sized and weighted vehicles with only PTC heaters. Our physics model accounts for the two heater types separately, which explains the visible differences in winter range between otherwise comparable vehicles on the heat pump comparison page.
Motorway versus urban driving: the influence of speed
Speed is the most significant factor affecting real-world efficiency. Aerodynamic drag increases with the cube of velocity; thus, doubling speed results in an eightfold increase in aerodynamic power demand. At 30 mph, rolling resistance is the dominant force, and most EVs achieve 4.5 to 6 mi/kWh. At 70 mph, aerodynamic drag becomes predominant, reducing efficiency to 2.5 to 3.5 mi/kWh for the same vehicle.
Owner-reported data corroborate this relationship. For example, the MG5 achieves approximately 3.8 mi/kWh at motorway speeds and over 5 mi/kWh in urban conditions. The BYD Dolphin demonstrates a similar pattern, ranging from 3.3 mi/kWh on the motorway to 5.0 mi/kWh or higher in urban settings. These differences align with the expected effects of aerodynamic drag.
For each vehicle in our catalogue, efficiency variations with speed are displayed on the respective car pages. The WLTP gap data page presents the motorway efficiency penalty for all models in a comparative format.
Aerodynamic vehicles compared to SUVs
At motorway speeds, vehicle shape has a greater impact on efficiency than battery size. For example, the Tesla Model 3, with a drag coefficient of 0.23 and a relatively small frontal area, experiences less aerodynamic resistance than the Kia e-Niro, which has a drag coefficient of 0.29 and a larger cross-sectional area. Consequently, the Tesla maintains its efficiency more effectively at higher speeds, whereas SUV-shaped vehicles exhibit a more pronounced decline.
Owner reports support these findings. The Kona Electric, which features relatively low aerodynamic drag and a compact body, consistently achieves 4.5 to 5.0 mi/kWh. In contrast, the Kia Soul EV, with its boxy design and a drag coefficient of 0.31, can reach 5.3 mi/kWh at an average speed of 30 mph but experiences a significant decrease at higher speeds. The physics model incorporates each vehicle’s drag coefficient and frontal area, explaining the variation in range estimates among models with similar battery capacities.
Model accuracy and limitations
For the 14 vehicles analysed, the physics model generally aligns with owner-reported efficiency ranges. The mean absolute error compared to the midpoint of owner reports is typically less than 10 percent. The model was developed using manufacturer specifications and first-principles physics, without calibration to owner data.
Instances where the model overestimates efficiency typically occur because the reference speed of 40 mph is lower than the owner’s actual driving conditions. Conversely, underestimation often results from predominantly urban driving at even lower speeds. The complete comparison for each matched vehicle is available on the model versus owner efficiency page.
Key practical insights
Drivers who primarily operate in urban and suburban environments can expect 4–5 mi/kWh in summer from most modern EVs. For frequent motorway travel, expect 2.5–3.5 mi/kWh, depending on vehicle shape and weight. In winter, reduce these figures by 15 to 25 per cent. Heat pumps are particularly beneficial on short, cold trips. Preheating the vehicle while it is plugged in provides additional efficiency gains.
Instead of memorising these figures, users are encouraged to input their vehicle details on the model pages and adjust speed and temperature settings to reflect actual driving conditions. The model calculates efficiency using the same physical principles that underlie observed owner patterns. All equations are documented on the methodology page.