What is an electric car heat pump and how does it work?
A battery heat pump could make a big difference to your electric car’s range and efficiency. Here we explain what it is and how it works...
Heat pumps. You may have heard about these as a sustainable way for heating your home, but they can also be found in electric cars. In fact, an increasing number of new electric cars are offered with a battery heat pump, either as an option or as standard, and they can have a big impact on range – particularly in colder weather.
Alongside regenerative braking systems and one-pedal driving, heat pumps are important to understand if you’re going electric. Here, we’ll explain what heat pumps are and how they work, and whether it’s worth ensuring your next electric car has one.
What is an electric car heat pump?
An electric car heat pump is a device that feeds waste heat from the car’s battery to the car’s interior to improve efficiency during cold weather.
This is a more efficient way of warming the car’s interior compared with using a traditional fan heater or air-conditioning system, because these draw a significant amount of power from the car’s high-voltage battery and reduce range.
In a petrol-powered car, the engine produces a great deal of waste heat, which is then used to warm the interior efficiently when needed. By comparison, the electric motor and battery in an electric car produce less waste heat; this is why a heat pump is required.
Another useful feature of a heat pump is that they can be used to keep the battery at the optimum operating temperature. Like humans, electric cars don’t operate as effectively in cold weather; the battery chemistry, specifically the lithium ions, move more slowly when it's cold, making it harder to operate as efficiently as they would in warm weather (the optimum temperature for electric cars is between 20 and 25deg C).
As a result, many new electric cars now come with a pre-conditioning setting, which allows the driver to warm up the battery before a drive or a charging session.
However, if the weather is too hot (electric car’s don’t like extremely hot weather, either) and the battery needs cooling, a heat pump can operate in reverse to improve the car’s efficiency and range.
How does an electric car heat pump work?
A heat pump is a device that consists of a compressor, a condenser, an evaporator and a series of pipes (which transfer compressed air between these elements).
The way it works is similar to a household fridge, particularly when the battery needs cooling; the heat pump draws waste heat from the car’s electrical components, compresses it, and then transfers the hot air to the evaporator, which then emits cool air when the pressure drops as the air is released.
If the heat pump needs to warm the battery or interior, warm air is emitted from the condenser and the evaporation process is skipped. Whether heating or cooling, a heat pump is highly efficient and it saves drawing energy from the car’s high-voltage battery, therefore improving range.
Is an electric car heat pump worth it?
Yes, but only if it’s offered with the car as standard. In our most recent winter range test, we drove two identical Volkswagen ID 7s – one with a heat pump and one without – until they ran out of power. Unsurprisingly, the car with the heat pump travelled farther (268 miles as opposed to 254 miles) because it was 5.2% more efficient.
However, because the heat pump is a £1050 option, we found that if you’re using the public charging network and paying 79p for every kWh of electricity, you’ll need to do 85,000 miles before you’ve recouped the cost. And if you’re charging at home, you’ll need to do even more miles.
Do heat pumps come as standard?
No, not all cars come with a heat pump as standard. Brands such as BMW, Porsche and Tesla offer them as standard on their electric cars, but others, such as Audi, Cupra, Kia, Skoda and Volkswagen offer them as an optional extra. Before buying an electric car, it’s worth checking the car’s specifications or asking the dealer whether a heat pump is offered with the car as standard.
Interestingly, all Renaults now come with a heat pump as standard in the UK. This is welcome news, because the Renault Megane E-Tech managed just 189 miles without a heat pump in our real-world winter range test – a 91-mile drop from its official range of 280 miles at the time.
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