Your Plug-in Hybrid Gives You Less in Winter, and Not in the Way You Expect

In winter a plug-in hybrid can start its petrol engine to heat the cabin. In two of three comparable cars in a four-car Canadian government test, the engine ran for about a third of the battery’s distance, against 5 per cent or less in summer, and that running accounts for most of the lost engine-off driving. A Volvo UK support page calls such starts sometimes needed and completely normal.

Key takeaways:

• Volvo’s UK support page says the petrol engine can sometimes start in the cold and calls that completely normal.
• In Canadian winter road tests, two of three comparable cars ran the engine for about a third of the battery’s distance.
• The heat pump car ran its engine for far less of it, and the paper names more than one reason.

The Engine Can Start When the Cabin Needs Heat

Driving on electricity is one job. In winter the cabin adds a second, and the petrol engine is standing by to help.

What a Volvo Support Page Says About Cold

Volvo’s UK support page for its XC40 plug-in hybrid says: “During electric operation, the car may sometimes need to start the internal combustion engine automatically due to external circumstances, e.g. in low outside temperatures, which is completely normal.”

The page, marked updated in March 2020, gives the reason: “In low outside temperatures, the internal combustion engine sometimes starts automatically in order to achieve the desired passenger compartment temperature and air quality.” It adds that low or high outside temperature can reduce electric range and output, changing how often the engine starts.

Under emission control, the page says the engine must run for several minutes once started, for a time that depends on the temperature of the catalytic converter, the part that cleans the exhaust. Volvo gives no temperature for low, and one maker’s XC40 does not speak for every plug-in hybrid.

How Four Cars Made Their Winter Heat

Environment and Climate Change Canada, the federal government department, road tested four 2018 model-year plug-in hybrids in 2019 and 2020 and recorded how each made winter cabin heat. Two used an electric coolant heater, one a heat pump and one had no electric heater at all.

The car with no electric heater needed its engine for every minute of cabin heat, and the engine started on all of its winter test days. The two coolant-heater cars started the engine at once too, then also drew on the battery to heat the cabin and to drive. The paper adds that the engine stayed blended into their driving, giving extra heat and propulsion.

The heat pump car moves heat from the outside air rather than making it. The paper credits the heat pump, the lower heating demand of a smaller hatchback and a strategy that put all-electric running first. The paper says the pump can operate effectively down to minus 10 degrees; below that the engine takes over. Full electric cars use the same part, and what a heat pump is worth in winter is a question of range for them.

What the Canadian Government Measured

The results table splits each test day into distance on the battery and distance with the engine off. The two columns tell different stories.

The Test, and Where It Stops Applying

Each car started from a full battery after a night outdoors, with the cabin set to 22 degrees and no pre-warming, a choice the paper says was made to simulate a worst-case cold start. Cars were driven on the road around Ottawa in summer 2019 and in winter 2019 and 2020.

The comparison uses one route, about 53 miles in two loops, which three cars drove in both seasons. The fourth, with no electric heater, was tested only in winter on another route, so it is left out. Distance on the battery is where the car stops relying on stored electricity. Distance with the engine off is the part of it driven without the engine running.

Three cars were compared, with two to five winter days each, and none is named. Winter days ran from about minus 15 to plus 6 degrees. The distance on the battery is an estimate fitted to road data, and none of this is a figure for a car on sale now.

The Battery Lasts, the Quiet Does Not

The two coolant-heater cars kept most of their battery distance. The people carrier covered 26 miles on its battery in summer and 24 in winter, the SUV 24 and 20. With the engine off, the people carrier fell from 25 miles to 16 and the SUV from 24 to 13.

Subtracting one column from the other gives the part of the battery’s distance with the engine running. In winter that was about a third, 34 per cent in both cars, against 5 per cent in the people carrier and under 1 per cent in the SUV in summer.

The heat pump hatchback lost more battery distance, 25 miles to 17, a fall of 31 per cent, but its engine ran for only 11 per cent of that. With the engine off it went from 25 miles to 16. The paper says it ran electrically from the start on mild and moderately cold days, yet its table shows the engine starting almost at once on a 2 degree day and a minus 4 degree day, and waiting 12 to 20 miles on three others.

Across the three cars the distance with the engine off fell by 35, 45 and 38 per cent. Day by day against each car’s summer average, the people carrier lost 29 to 42 per cent, the SUV 43 to 46 and the heat pump car 22 to 53. The days follow no single pattern: the people carrier’s mildest day was its worst, while the heat pump car’s mildest was its best. With two to five days per car, the table cannot say why. The loss is real in all three cars, and it is not the same loss.

What an Owner Can Do About It

The levers are few, and the sources read for this piece publish no saving for any of them.

Heat the Car on the Charger

SEAT published its winter advice for the Leon e-HYBRID on 21 January 2021. Francesc Sabaté, head of Energy Systems Development, says “the best solution is to turn on the car’s heating or activate the heated seat and steering wheel functions remotely using the SEAT Connect app a few minutes before getting into the car, with the vehicle still connected to the charger”.

Sabaté gives the reason: “This way the interior of the vehicle will be warm when you get in, without the need to use battery power to achieve this once you start your journey”. Volkswagen UK and Nissan say the same of full electric cars: warming up on the cable leaves the battery alone.

The Canadian paper said electric pre-heating could cut the cold-start fuel penalty in the two coolant-heater cars, and did not quantify it. The car with no electric heater could not use it. SEAT’s page adds a catch for very cold weather: with the car left plugged in to pre-heat its battery, the vehicle starts off in combustion mode.

The Settings That Change Engine Time

Volvo’s start and stop page lists three things that can affect how long the engine runs in low temperatures: a lower temperature setting, a lower fan speed and its Pure drive mode.

Pure also trims the climate system. On Volvo’s XC40 Recharge Plug-in Hybrid drive modes page, marked updated in March 2023, it switches on eco climate control and reduces several electricity consumer functions. Full climate function returns on leaving Pure or adapting Individual drive mode with full climate functionality, and the maximum defroster button keeps normal function. Low outside temperature can make Pure unavailable.

Heated seats and a heated steering wheel warm the person rather than the cabin air. What heated seats and wheels draw is small beside the main heater.

In two of the three comparable test cars the battery went within four miles of its summer distance, and what winter took was the engine-off share, with the engine running for heat and blended driving. The heat pump car lost more battery distance but kept its engine quiet for longer. Heat on the charger works as it does in a full electric car, and the Canadian paper did not measure what it saves.

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Reviewed by Preetam Gadekar