A recent study from AAA claims that electric vehicles (EVs) lose significant range in below-freezing temperatures, revealing that Tesla vehicles lost 41% of range in study findings. The drop is caused when the HVAC (heating, ventilation and air conditioning) system is used to heat the interior of the vehicle, which ultimately consumes significant energy that could be used on the car’s mileage. However, despite AAA’s research, Tesla have claimed that the data from their own vehicles is not “anywhere near” what AAA report suggests.

AAA’s research explains that “in order to facilitate the development and uptake of EVs, traction batteries with high specific energy, high current capability, long cycling life and low production costs are essential. To meet these requirements, Li-ion batteries are currently utilized within EVs”. This therefore means that “the driving range of any EV is determined by two factors, the capacity of its fully-charged battery pack and the efficiency of its electric powertrain. With most EVs, one kWh of electrical energy from the battery pack will provide between two to four miles of driving range. The EPA publishes range estimates for all EVs, but real world results can, and do, vary based on several factors, [which are] battery temperature, interior temperature, driving habits and operating conditions”. All of these factors are influenced in extreme weather conditions, particularly snow.

The study conducted by AAA took various vehicle brands into consideration, including Nissan, Chevrolet, Volkswagen and BMW. AAA’s overall key findings were:

AAA’s overall key findings were…

In isolation, hot and cold ambient temperatures resulted in modest reductions of driving range and equivalent fuel economy. Driving range and equivalent fuel economy reductions slightly differ due to the temperature dependency of both the recharge allocation factor (RAF) and battery discharge capacity.

On average, an ambient temperature of -6.6°C (20°F) resulted in a 12 percent decrease in combined driving range and a 9 percent decrease in combined equivalent fuel economy (when compared to testing conducted at 23.8°C (75°F)).

On average, an ambient temperature of 95°F resulted in a 4 percent decrease in combined driving range and a 5 percent decrease in combined equivalent fuel economy (when compared to testing conducted at 23.8°C (75°F)).

HVAC use results in significant reductions in driving range and equivalent fuel economy.

On average, HVAC use at 20°F resulted in a 41 percent decrease in combined driving range and a 39 percent decrease in combined equivalent fuel economy (when compared to testing conducted at 23.8°C (75°F)).

On average, an ambient temperature of 35°C (95°F) resulted in a 17 percent decrease in combined driving range and an 18 percent decrease in combined equivalent fuel economy (when compared to testing conducted at 23.8°C (75°F)).

Depending on ambient temperature, HVAC use results in a significant monetary cost increase.

Despite these results, a spokesperson for Tesla told FORWARDER: 

Based on real-world data from our fleet, which includes millions of long trips taken by real Model S customers, we know with certainty that, even when using heating and air conditioning, the average Model S customer doesn’t experience anywhere near that decrease in range at 20 degrees Fahrenheit, and the decrease in range at 95 degrees Fahrenheit is roughly 1%.   

Furthermore, Tesla note that AAA’s tests were based on a complete discharge of the battery from full to empty, which does not fully represent real-world or everyday usage of a vehicle. Telsa voices that distances of 50 miles or more are categorised as “long trips” in everyday use of the vehicle.

Recent claims that EV batteries’ range shrink in the cold, which Telsa claims is a misreport. This statement around EV batteries suggests that the range loss Tesla vehicles experience in extremely cold temperatures is due to the impact of the temperature on the battery. Tesla disputes this claim, explaining thatthe primary reason for shorter range is the impact of the cold on overall energy usage (i.e. MPG and MPGe). This affects gas-powered cars, in addition to EVs.

Tesla spoke with high confidence in their vehicles, stating that their electric vehicles are designed to be both inherently more efficient and minimal in terms of energy waste in comparison to traditional cars, meaning that the vehicle is built to handle features that consume energy (such as HVAC systems). Despite AAA’s findings, Tesla explained that various impacting factors of colder or below-freezing temperatures may have an affect on both EVs and internal combustion across electric vehicles in general. For example, in cold conditions, the rubber in tyres compounds, dissipates more energy when cold, subsequently increasing aerodynamic drag due to the higher density of cold air, meaning more energy is used. Additionally, oil in a car’s gearbox becomes thicker in colder temperatures, which affects the vehicle’s performance as a result. Whilst these factors are relevant to gas vehicles, gas engines in fact disposes around 75% of the energy in its gasoline during everyday driving, altering the significance of energy waste. According to Tesla, electric motors typically throw away less than 15% of the battery’s energy during everyday driving.

Rachel Jefferies, Editor, FORWARDER magazine  

AAA study results taken from AAA’s February 2019 Electric Vehicle Range Testing