Electric cars to create new peak hour when they all need a charge

At today's adoption levels, electric vehicles' impact on overall household energy consumption is negligible, but grid planners probably need to look to the future sooner rather than later.

Research conducted by Matteo Muratori of the US Department of Energy's National Renewable Energy Laboratory (NREL) finds in the medium term, electric vehicle (EV) charging has more impact on demand peaks than overall household energy consumption.

Opponents of EVs often mention the vehicles' electricity consumption, but the NREL study found at any penetration below three per cent – that's 7.5 million vehicles into the US market – there's no significant impact on overall residential electricity consumption.

At the end of 2016, the US EV fleet comprised only 600,000 vehicles, so there's years to go before there are enough EVs to show up in the statistics.

What's more likely, the researchers found, is that EV adoption will melt the odd transformer if electricity distributors don't prepare for their arrival.

As the NREL release stated: “a problem arises when motorists gathered in a geographic area began buying these vehicles and plugging them in to recharge upon returning home”.

A relatively small amount of clustering will “significantly increase the peak demand seen by distribution transformers and might require upgrades to the electricity distribution infrastructure,” the paper said.

The impact on local grids will be even more marked if significant numbers of users adopt Level 2 chargers (recommended by most manufacturers for home chargers, if the customer doesn't have access to a manufacturer's charging station), the paper said. In that case, “the distribution infrastructure might no longer reliably support the local electricity demand” and demand could shorten transformer life.

Muratori says grid planners should try to adopt a coordinated approach to supporting EVs, and notes that his study didn't include any potential “return to grid” from vehicles' batteries.

The research landed in Nature Energy this week, and Muratori has published the data used in the study here. ®