In a traditional petrol or diesel car, the heat for your cabin is produced using waste heat from your engine. So how does an EV manage it? What are the pros and cons of an EV heating system?
How does it work?
An engine or motor wastes energy creating heat as a by product of it’s operation. A highly efficient electric motor produces very little heat so the air temperature must be raised by some other means. In early EVs, this meant the use of a simple resistive heater like the one found in a fan heater or electric fire. This was a superbly inefficient use of power and something that manufacturers quickly strived to move away from.
All modern EVs prefer the use of a heat pump system. This is a familiar heating system to anyone interested in eco-homes or sustainable building. A heat pump works very much like an air conditioner and is capable of moving heat into the cabin at efficiencies over 100%.
A conventional heater converts electrical energy into thermal energy. The heat pump takes thermal energy from the outside air and compresses it before releasing the heat inside. A super efficient heat pump can generate over 4kW or thermal energy for every 1kW of electrical energy used.
What are the Negatives?
All EVs have one primary source of power, their traction batteries. As such, this power must be shared between the heating system, other ancillary systems, and the driving motors of the car. Any power used for heating comes at the expense of power available for other purposes. In 2009, when first generation EVs came out, this caused significant losses of range in Winter.
This compromise is severely reduced in the modern electric car; often to the point it becomes irrelevant for an EV owner. Current heat pump heating systems are many times more efficient than the original systems and battery sizes are much greater. As such, current EVs only suffer fractionally from the use of heating in Winter and comfort no longer needs to be sacrificed for range performance.
What are the positives?
Have you ever sat in your car waiting for 15 minutes for hot air to defrost your car and warm your frozen hands? With an EV this is no longer an issue.
The heat pump system can produce warm air within seconds for an instant boost of heat. Even better than this, you can warm up and defrost your car without leaving the comfort of your home Using an app or timer, your EV can defrost itself in the morning whilst you eat your cereal.
Not only this but leaving your petrol/diesel car unlocked and running outside your house is a serious security risk. A number of cars are stolen every year whilst warming up outside. In many cases insurance will not cover theft of a vehicle left running unattended. With an EV, your keys stay safe inside with you and your car is turned off and locked the whole time.
So do we love EV heating systems?
With the modern EV heating system, it is hard to find a downside. Larger batteries and high efficiency heat pumps have removed range anxiety and the giant steps forward in convenience and comfort make getting back into a conventional vehicle a winter nightmare.
You will be the envy of your neighbours when your new EV is steaming clear whilst they scrape their windows.
Bonus – Driving on Snow and Ice
An electric car is often at an advantage when driving in snow and ice. With no gears and an ultra-smooth motor, you are far less likely to slip and slide when accelerating.
The narrow eco tyres on many electric cars can also help, aiding grip on packed snow.
The power characteristics of an electric motor mean that it is very easy to pull away and minimise wheel spin with an electric car. Simply release the handbrake and gently touch the accelerator and the smooth power delivery will usually allow the car to pull away with minimal fuss.
Electric car owners can use regenerative braking – where the motor progressively slows the car and uses the motion of the wheels to recharge the batteries – to provide far smoother and safer braking.
The method for slowing a car using regenerative braking does vary between models. On the BMW i3 or Mitsubishi i-MiEV, for example, simply taking your foot off the accelerator will activate the regenerative braking, gently slowing the car down to walking pace before you apply the brakes to bring the car to a halt. On the Nissan LEAF, gently touching the brake pedal activates the regenerative braking.
Because the motor is used for both accelerating and braking, the overall balance of the car remains more consistent. This is a significant benefit when driving on ice or slow. Regenerative braking reduces the chance of skidding or sliding and minimises the risk of losing control of the car. Overall braking distances are similar to other cars braking gently in slippery conditions.