What’s a heat pump and why should I care?
A heat pump is more or less exactly what it sounds like. It’s a pump that takes warm air or liquid from a source, and then increases the temperature by compressing it. The increased temperature air or liquid can then be circulated around something that you’re sitting in, be it a car or your house. Basically, it’s like the compressor on your fridge, but working in reverse.
Why you should care is because having a heat pump heating system can help to significantly extend the one-charge driving range of your electric car when the weather turns chilly.
According to Martin Dunne, Peugeot Ireland's technical guru: "Peugeot has opted for what is called a dual indirect heat pump. Indirect, because the heat pump heats a water circuit that will then pass through the air heater. Double, because the system uses a second water circuit. It's the reverse to our house hold refrigerator, with a fridge we take the heat out from the inside and release it to outside, with a heat pump the heat is taken from cooling of the battery and drive train and fed inside the vehicle.
"As well as the heat pump we also have a 400-volt water heater and a 12-volt air heater fitted to our e-CMP vehicles [such as the e-208 and e-2008]. We would say the advantage of having a heat pump is that for 1kW of electricity consumed we provide between 1.5 to 3kW of heating. The difference depends on the outside temperature. The ideal outside temperature range for maximum efficiency of the heat pump is between 5 to 15 deg Celsius which is where our temperature in Ireland is more than 80 per cent of the time."
Is this why my EV has less range in the winter?
Partly so, yes. Any electric car battery is going to perform less well in very cold conditions, because the chemical reaction that takes place inside the battery, the thing that actually generates an electrical current, slows down as the temperature drops. So the battery has to work harder, and the cooling and heating circuit that tries to stabilise the battery’s temperature has to work harder too. All of which adds up to increased drain on the battery.
A heat pump really helps with all of that, as it can draw excess heat from the electric motor and the battery (both of which heat up with use) and distribute that heat to your car’s cabin, warming it up faster and more efficiently on cold winter days.
How much energy can a heat pump save me?
As with anything, this will vary hugely from car to car, but according to Kia, the heat-pump heating system in the eNiro electric crossover draws about 1.75kW when you're running it, compared to 5.5kW for the conventional heating system. That's a massive saving, especially when you're trying to stretch battery capacity to its limits on a long drive.
Does it help with air conditioning as well?
No, not really. The clue is in the name. Air conditioning, thanks to the increasing efficiency of air-con systems, doesn't drain your battery half as much as it used to. For an example of that, look at the recent test carried out by consumer group Which? .To see if being stuck in traffic could potentially leave you stranded with a flat battery, Which? took a new Volkswagen ID.4 and left it standing still with the headlights on, the infotainment streaming from Spotify, the heated seats on, and the air conditioning going full blast. Even with all that drain, the VW lost only two per cent of its total battery charge in just over an hour.
By contrast, heating the cabin uses much more power. A back-to-back test in Canada, using a Kia eNiro, found that the car had a maximum range of about 310km in chilly conditions, of between -6 and +4 degrees Celsius, using the cabin heating. By contrast, in mid-June, with summer temperatures outside, and the air conditioning going, the same car had a calculated range of 434km.
So why don’t more EVs come with standard heat-pumps?
We asked Volkswagen about this, as its popular ID.3 and ID.4 models are conspicuous in offering a heat pump only as an expensive, €1,142, optional extra. “The efficiency is mainly noticed when exterior temperatures are less than zero degrees Celsius. Due to Ireland’s temperate climate - annual averages range from 7 - 19 degrees Celsius - the benefits of a heat pump may not be realised versus a colder climate, such as found in Scandinavia for example” said a VW spokesperson in response.
“The heat pump is available as an optional extra on the ID.3 and ID.4 and it is standard on the ID.4 Max and ID.4 GTX Max trimlines. and we currently have a take-up rate of approximately two per cent in Ireland on this feature.”
So, do I actually need one?
Yes, you do. Okay, so maybe our temperate climate doesn’t really push an EV battery to its extremes, but it’s still nice to have a toasty-warm cabin when you need it, and every bit of extra efficiency helps, not only when undertaking long journeys, but also in squeezing as much motive use as possible out of each kWh of electricity put into your battery when you charge up.