Free Online Calculators
Battery capacity + charge power โ charge time & energy
Find out how long it takes to charge your EV and how much energy goes into the battery. Enter your battery capacity, current and target charge level, and charging power. Up to 80% the calculator uses charge time = kWh to add รท charging power (kW); above 80% it doubles the time. It does not calculate electricity cost or charging losses.
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Divide the energy you need to add (battery capacity times the state-of-charge gap you want to close) by the actual charging power, then add a margin for losses and for the slower taper near the top of the battery. The limiting factor is always the lower of the charger's output and the car's maximum onboard AC or DC charging rate.
It's the habit of keeping the battery roughly between the lower and upper fifths of its range instead of routinely charging full or running it near empty, which reduces stress on lithium-ion cells. On DC fast chargers it also saves time, because charging speed drops sharply once the pack is well filled.
On a home wallbox it typically takes a few hours to fill the remaining half, while a DC fast charger can do the same in well under an hour. The exact time depends on battery size, the car's maximum charging rate, the charger's power and the target state of charge.
No โ for daily use most manufacturers recommend a lower daily charge limit and full charges only before long trips. Leaving the pack sitting at full for long periods accelerates capacity loss, though LFP batteries are an exception and should be charged full regularly.
High-speed driving is the biggest drain, because aerodynamic drag rises steeply with speed; cabin heating in cold weather is the second-largest factor. Cold temperatures, hilly terrain, heavy loads, low tyre pressure and roof boxes all add to consumption as well.
Yes, plugging in overnight is sensible in winter โ the car can keep the battery warm and preconditioning runs on mains power instead of the pack. Set a charge limit below full rather than charging to the maximum every night.
Yes, but very little โ parked cars lose a small amount per week to standby systems, alarm, connectivity and battery management, often called vampire drain. Losses grow if sentry or preconditioning features stay active, so switch them off before longer parking.
Charging time depends on two main factors: how much energy your battery needs and how fast your charger can deliver it. The basic formula is simple โ divide the energy needed (in kWh) by the charger's power output (in kW) to get hours. For example, charging a 60 kWh battery from 20% to 80% means filling 36 kWh. On a standard 7.4 kW wallbox, that takes roughly 4.9 hours. On a 50 kW DC fast charger, the same session takes under an hour.
Real-world charging is a bit messier. Onboard charger limits, battery temperature, and the tapering effect near full charge all reduce actual speed. This calculator keeps it simple: it divides the energy by the charging power you enter up to 80%, and assumes half the speed from 80% to 100%. It does not add charging losses.
A regular household outlet (Level 1, around 1.4โ2.3 kW) is the slowest option. Adding 36 kWh at 1.4 kW takes over 25 hours โ fine for overnight top-ups on a short commute, but not practical for a larger EV or a quick turnaround. Most EV owners only rely on this as a backup.
A home wallbox or Level 2 charger (7โ22 kW) is the sweet spot for daily use. In the calculator, a 22 kW wallbox charges a 77 kWh battery from 0 to 100% in 4 h 12 min; at 7.4 kW it takes 12 h 29 min, because the last 20% count double. DC fast chargers (50โ350 kW) are built for highway stops, where a short session adds a lot of energy on a compatible vehicle.
Knowing your charger's actual output โ not just its label โ matters a lot. A 22 kW wallbox means nothing if your car's onboard AC charger maxes out at 11 kW. The calculator has a single charging power field, so enter the lower of the two values yourself.
The calculator does not show cost or range, but both follow from the charging energy it displays. Cost = energy ร price: at $0.25 per kWh, adding 36 kWh costs about $9 โ a little more in practice, because charging losses are not included.
Range added = energy รท consumption. A car consuming 18 kWh per 100 km gains about 200 km of range from 36 kWh. A less efficient SUV at 25 kWh/100 km gains closer to 144 km from the same charge.
Divide the energy you need to add (kWh) by your charger's output (kW). For a 7.4 kW wallbox adding 40 kWh, that's roughly 5.4 hours. Always use the lower of your charger's power and your car's maximum AC acceptance rate.
Yes. Most EVs slow down charging above 80% to protect the battery. The calculator models this simply with half the charging speed above 80%: a 60 kWh battery at 11 kW needs 3 h 16 min from 20% to 80%, and 5 h 27 min from 20% to 100%.
A 7.4 kW wallbox might take 8โ10 hours for a full charge, while a 100 kW DC fast charger can do the same in under an hour. Fast chargers are ideal for road trips; wallboxes suit overnight home charging.