Too many electric cars charging at night may overload electrical grid

The growth in electric car ownership could strain power grids if most drivers continue charging primarily at home overnight. Investment in daytime charging options will be crucial to help the western US power grid handle the demand with an estimated 50 per cent of drivers using electric vehicles by 2035.

That finding comes from computer models looking at how driver charging behaviours and available charging station infrastructure at home and in public places could impact peak net electricity demand – the highest electrical power demand minus power provided by solar and wind power.

If drivers primarily charge vehicles at home during the night, that could lead to a 25 per cent surge in peak net electricity demand when states reach 50 per cent electric vehicle ownership, and possibly surpass grid capacity at even higher levels of ownership. But expanding daytime charging opportunities could reduce that increase in peak net electricity demand to just 7.5 per cent and help reduce the costs of expanding grid capacity.

“One of the big results from our study is that just making the shift of which charging infrastructure you build and where you encourage people to charge is a huge difference in the result for the grid,” says Siobhan Powell at the Swiss Federal Institute of Technology in Zurich, Switzerland, who led the research while at Stanford University in California.

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