If you jump in a petrol or diesel car on a cold morning, the engine warms up quickly by the process of combustion. The heat generated is fed into the coolant which surrounds the engine and part of this can be diverted into the car’s heating system.
Until this happens, switching on the air-conditioning puts a load on the battery and the air-conditioning pump, impacting fuel consumption. If the engine is allowed to cool this happens over again.
In order for an electric car battery to function properly, a constant temperature must be maintained. The ideal operating temperature of an EV battery is around 20-40 degrees Celsius, depending on the car model.
When the temperature drops, the chemical reactions inside the battery slow down. EV batteries are either surrounded by a liquid, which can be used both to cool the battery and to warm it up, or are air-cooled.
What sort of drop in range are we talking about?
Glance at many of the car magazines’ reports on daily life with EVs they’re living with and it’s usual to see that the official range is often not met, and drastically reduces further when it’s cold.
In Winter 2023, the driver of a Ford Mustang Mach-E found the peak range of 226 miles (officially 273) dropped to 180 miles in February, partly due to having to often keep warm waiting to collect his kids. In the same period the driver of a Skoda Enyaq experienced a power consumption equivalent to 100 miles of range during a cold snap making lots of short journeys (it was averaging 220 miles to a claimed 323 miles).
Carmakers are upfront about this loss in range – you can’t get away from it. For example, the Renault website section on the Megane E-Tech has a range simulator where you can change parameters. At 30mph with an outside temperature of 20°C and no heating or air conditioning on and in ‘eco mode’, it has a range of 299 miles. At 30mph at 10°C and heating on, this shows 228 miles.
Short trips that allow the cabin to cool in between are the least efficient because you’ll want to use the heater and the battery management system needs to maintain the battery itself at optimal temperature.
If you do a series of short trips with parked periods of sufficient length for the car to cool to an ambient temperature, you’ll see a relatively significant reduction in your miles per kWh, up to 30%. The good news is that these short journeys fit well with quick top-up charges such as supermarket runs.
What kind of heaters do EVs have?
Internal combustion-engined cars generate heat as soon as they are running, and the water in the coolant system absorbs some of that heat. After a few miles you can get some heat into the cabin and using the air conditioning (which will heat and de-mist as well as cool) will boost this. EVs have high-voltage electric heaters and an electrical air conditioner
In case you were wondering, EVs still have a traditional lead-acid 12-volt battery to run the accessories and lower-voltage control systems.
Cold weather EV tips
- If you have one, parking in the garage overnight is always a good start – you’ll avoid the need to defrost and keep the ambient air temperature up.
- Plug in at home as soon as you arrive. If an EV is plugged in and charging the car it is also pre-conditioning, or pre-heating the battery. On some cars you can also program the interior heating system from your smartphone or hands-free card before starting your journey. By the time you open the car door, the cabin will already be at a comfortable temperature and you won’t be decreasing your vehicle’s range. If pre-conditioning is initiated while the car is connected to a power supply, the energy necessary to heat the interior will come directly from the grid. It’s the cheapest way to charge and you have normal range to start off with.
- If you have them, activate the heated seats and steering wheel (some EVs have heated seats front and rear) before the heater. They use a lot less power than an electrical heater and you can turn the overall system down a few degrees. If you have two-zone or three-zone climate control and you are alone in the car, only heat the driver area if possible.
- Opt for the ‘Eco’ driving mode, which automatically optimizes your energy consumption by regulating heating, acceleration, cruising speed, and braking. This feature will allow you to gain up to 10% more range. It’s especially useful on longer trips.
- If there is snow ice (or more likely) heavy rain about, it’s a good idea to adopt a gentler style of driving in any car and slow down. Regenerative braking is useful at all times of year; it allowing electricity generated by letting the car slow itself to be fed back into the battery. When you take your foot off the throttle, the car regenerates power – it uses the electric motor in the rear to brake, converting the kinetic energy into electrical energy, which is then stored in the battery.
- As with a petrol or diesel car, shedding any unnecessary weight or drag will make it go further. So, take off the roof rack after the holiday and clear out the boot (except for the charging cable of course).
- Likewise, keep your tyres inflated to the correct pressures. If you have fitted winter tyres switch back to summer tyres as soon as possible to increase range.
In addition, the speed at which the battery can take a charge slows down if it’s cold. Charging company Mer suggests that if you’re not able to preheat your EV’s batteries in advance of a trip, you wait as long as your vehicle will allow before a charge. This way, the battery at least has time to get lukewarm – making charging both better for the battery and faster.
Do I need a heat pump?
A heat pump boosts the electric heater in an EV and can help preserve range. It uses the heat generated by the cars electrical components to vaporize refrigerant from liquid to gas form. High-pressure gas is discharged from the compressor and forced into a condenser to be converted back into a liquid. This process generates additional heat energy that is recovered by the heat pump and used to warm the cabin. Some EVs recycle additional waste heat from the power electrics (PE) modules (such as drive motors, on-board chargers, and inverters), and also from the battery pack and slow charger.
It takes a bit of digging to find out, but some EVs have heat pumps fitted as standard, such as all Vauxhall Corsa Electric models (from £35,125) and sister car the Peugeot e-208, as do the Hyundai Kona Electric (from £32,450) and Kia Soul EV (different brands, same hardware). Some Chinese brands are including heat pumps as standard, for example BYD, due to launch in the UK later this year with the starting price of its Dolphin model £25,490.
Some more expensive cars – which have larger batteries – leave it on the options list on for the top trim levels. A heat pump for a Volkswagen ID.3 (from £37,115) is £970 and a pump for a Hyundai Ioniq 5 in its two lowest trim levels (from £43,445) is £995. However, a quick look at internet discussions from UK EV owners shows some wouldn’t spend the extra again on a heat pump, even though they were effective.