For most EVs, Level 2 charging adds 20-30 miles of range per hour of charge and will fully charge your vehicle in 7-10 hours.
Three hardware factors determine how long it takes to fully charge your EV:
- Vehicle battery capacity: This is the amount of energy that the battery can store and is measured in kilowatt-hours (kWh). Most manufacturers provides both a gross battery capacity, the total amount of energy that can be stored by the battery, and usable battery capacity, the energy that can be safely discharged by the battery. Most EVs have a usable capacity that is 90-95% of gross capacity.
- EV wall charger (EVSE) power output: Your EV wall charger sends AC power from your home to your vehicle. Its power output is measured in kilowatts (kW). Power output is calculated by voltage x amperage. The voltage for all Level 2 chargers is 240V. Amperage varies by model and is typically 32A, 40A or 48A, yielding a power output of 7.7kW, 9.6kW, and 11.5kW, respectively.
- Vehicle onboard charger (OBC) power output: Your vehicle’s OBC converts the AC power from your EV wall charger into DC power stored by your vehicle’s battery. It’s power output is measured in kilowatts (kW). Most EVs today have an OBC power output between 6.6kW and 11.5kW.
You can estimate the time to fully charge your vehicle by dividing the usable battery capacity (kWh) by the maximum power the battery can receive. This is limited by both your EV wall charger and your vehicle’s OCB - whichever has a lower power output. For example, a Tesla Model 3 Rear-Wheel Drive has an OBC power output of 7.7kW. This means that even if you use a Tesla Wall Connector that has a maximum output of 11.5kW, the vehicle will still only charge at 7.7kW because maximum power is limited by the OBC.
There are two environmental factors that also effect charging speed:
- Vehicle state of charge (SoC): State of charge is how “full” your battery currently is i.e. the amount of energy currently stored as a percent of total. Batteries charge fastest when they are at a low SoC or nearly empty.
- Temperature: EV battery charge fastest in moderate ambient temperatures - neither too hot nor too cold. An Idaho National Laboratory study found that at 32°F, EV batteries took in 36% less energy vs. at 77°F, taking longer to charge.
If you're still deciding what charger to get, check out the Treehouse EV charger guide.
Treehouse can help you calculate charging speed for your specific vehicle, charger, and home setup.