Is it safe to charge your EV overnight?

Most EV owners charge their vehicles overnight, according to the U.S. Department of Energy and the U.K. Department for Transport. This routine is supported by battery management systems that disconnect the power when the battery reaches 100%, preventing overcharging. Some EV models also reduce the charging speed near full capacity to minimize battery stress, according to Chinese charging solutions provider Wise Energy.

Many EVs include scheduled charging features, allowing users to set charging times during off-peak hours and stop charging at a chosen percentage. This function not only helps maintain battery health but can also reduce electricity costs.

Overnight charging is favored for both convenience and lower energy costs. Electricity rates tend to drop at night when demand on the grid decreases, particularly for consumers on specialist EV tariffs, as reported by U.K.-based home energy provider BOXT. For around 80% of new car buyers who can charge at home, the cost per mile is generally lower than that of gasoline-powered vehicles, Car and Driver noted.

An electric car is charging. Photo from Pexels

While overnight charging is considered safe, experts advise against fully charging an EV battery every day. Lithium-ion batteries, commonly used in EVs, can degrade more quickly when regularly charged to 100% or allowed to drop below 20%.

BOXT reported that battery wear is primarily affected by two factors: the number of charging cycles and the amount of time the battery remains above 80% or below 20%. Leaving a vehicle plugged in every night to reach full charge can reduce the battery’s long-term capacity and driving range.

To extend battery life, experts recommend maintaining a charge between 20% and 80% for regular use. A full charge should be reserved for long-distance travel or unusually high daily mileage.

Drivers covering fewer than 50 kilometers per day typically need to charge only every two to three days. Some smart EVs and mobile applications support scheduled charging that completes just before departure, reducing the time the battery spends at 100% and preserving its condition.