BackupBatteryDepota sizing guide, not a store

Charging an electric car at an off-grid cabin

A power station can charge a car, but slowly and not far. One full station adds roughly 7 to 8 miles at normal household-outlet charging speed.

How fast cars charge

Type of chargingEPA saysDepartment of Energy says (2016)
Household outlet (120 V), called Level 1About 5 miles of range per hour, assuming 1.9 kW2 to 5 miles per hour
240 V circuit, called Level 2Not shown. The two sources give different miles per hour.

The two sources line up on the household-outlet speed. They give different figures for 240 V charging, so that number stays off this page. The Department of Energy page dates from 2016, and both say speeds vary by car and charger. Level 1 only

Sources: EPA, Plug-in Electric Vehicle Charging: The Basics; Department of Energy, Fact #919 (Apr 4, 2016). Read Nov 5, 2026.

What a station adds

EPA's numbers work out to about 380 Wh per mile (1,900 W for 5 miles). That's our arithmetic from EPA's figures, not an EPA number. We also assume 15% of the energy is lost on the way from battery to car. Change that in the sizing tool.

StationStored energyMiles it adds at household-outlet speed
BLUETTI Elite 3003,014 WhAbout 7 miles
EcoFlow DELTA Pro3,600 WhAbout 8 miles

Why the faster kind is out

EPA's faster example draws 6.6 kW. The most either station can put out is 2.4 kW (BLUETTI) or 3.6 kW (EcoFlow). So these stations can only do the slow kind.

What we haven't found