Electric vehicles will increase winter electricity peaks, study finds

New University of Otago—Ōtākou Whakaihu Waka research shows electric vehicle owners will need to charge their cars more in winter than in summer, leading to an increase in the winter electricity peak by 2050.

Led by Associate Professor Michael Jack, director of the Sustainable Energy Program in the Department of Physics, researchers investigated the impact both different seasons and regions have on charging electric vehicles (EV) and Aotearoa New Zealand’s electricity grid.

They found electricity consumption for vehicle charging can vary seasonally by up to 16%, and in some regions could increase winter monthly consumption by up to 30% by 2050.

“While internal combustion engines use waste heat, electric vehicles require energy from their batteries to heat their passenger cabin and regulate their battery temperature, so it is expected they will need more energy per kilometer in colder weather,” Associate Professor Jack says.

“This seasonal variation in energy for charging electric vehicles, like that caused by space heating, is challenging to address in a future renewable-dominated electricity grid.”

While a rise in electric vehicles (EVs) will help reduce future emissions, the additional demand for charging may place pressure on Aotearoa’s electricity grid by creating peak loads.

Previous studies have focused on daily variation in charging and ways it can be shifted into off-peak periods, but less on seasonal variation.

Using data from the citizen science organization Flip the Fleet, Associate Professor Jack and fellow researchers built a statistical model of the energy efficiency of EVs across the four seasons. Results were published in the journal Energy.

“We combined this with future projections of electric vehicle uptake, to quantify the seasonal variability in electric vehicle charging and its impact on future winter electricity peaks,” he says.

The researchers tested their model on a range of EV models available in the Aotearoa market.

“Interestingly, in addition to having very different baseline efficiencies, different vehicle models were also impacted by cold weather in varying ways,” Associate Professor Jack says.

Due to temperature variation throughout Aotearoa, there can be up to 18% variation in energy efficiency between regions for the same vehicle, while vehicles in colder climates can use up to 16% more electricity in winter.

“Buyers of electric vehicles should be aware of this sensitivity to climate. The results indicate that EVs will place significant pressure on regional lines capacity, particularly in colder areas, with important implications for future electricity infrastructure planning.”