Nighttime EV charging creating future strain on grid capacity

The vast majority of US electric vehicle (EV) drivers with domestic chargepoints power batteries up in the evening, but this is unsustainable and may even increase air pollution. 

A new study conducted by Stanford University has pointed to an urgent need for a change in habits among those who have made the switch to low emission cars in order to avert a rapidly growing problem relating to overall grid capacity. Put simply, if everyone connects their motors to recharge at the same time, peak-time demand will exceed capacity. 

Results published in the journal Nature Energy show that in the western United States, by 2035 power demand could increase by 25% at peak times if residential, nighttime EV charging continues to be the dominant method. This would put significant strain on infrastructure, and require expansions to existing power sources, and the development of new ones. Not only would that greatly increase the cost of provision, the environmental impact would also be notable. 

Further to the green issues with building new power plants and other facilities, spikes in demand of any kind always lead to an increase in emissions associated with power generation – the more power generated at one time, the more emissions. As such, despite having chosen EV models in a bid to help with overall efforts to reduce pollutants being released into the atmosphere, by charging at the same time drivers are creating more emissions than necessary. 

‘We encourage policymakers to consider utility rates that encourage day charging and incentivize investment in charging infrastructure to shift drivers from home to work for charging,’ said the study’s co-senior author, Ram Rajagopal, Associate Professor of Civil and Environmental Engineering at Stanford.

‘We considered the entire western US region, because California depends heavily on electricity imports from the other western states. EV charging plus all other electricity uses have consequences for the whole western region given the interconnected nature of our electric grid,’ added Siobhan Powell, lead author of the study. ‘We were able to show that with less home charging and more daytime charging, the Western US would need less generating capacity and storage, and it would not waste as much solar and wind power.’ 

In California, widely recognised among the most climate-aware US states, around 1m cars and light trucks are currently electric – roughly six percent of all vehicles on the region’s roads. By 2030, policymakers want to hit 5m EVs. Once penetration hits 30 to 40% of all cars the grid will experience major stress without large scale investment, and new charging habits. You can read a detailed report on the research here. 

In the UK, local authorities have been criticised for falling behind on the rollout of charger installations, while the government has promised to increase the number of charge points tenfold by 2030.

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