Charging an electric vehicle is, at heart, filling a battery measured in kilowatt-hours at a rate measured in kilowatts. This calculator finds the energy needed to go from your current state of charge to your target — a fraction of the battery’s capacity — then divides by the charger’s power to estimate the time. It separately accounts for charging losses (energy drawn from the grid is a bit more than what reaches the battery, typically 85–92% efficient) to compute the electricity cost at your rate. The charger power makes the biggest difference: a Level 1 outlet (~1.4 kW) takes many hours, Level 2 home charging (7–11 kW) suits overnight top-ups, and DC fast charging (50–250 kW) adds range in minutes. Note that DC fast charging deliberately slows above about 80% to protect the battery, so real fast-charge times past 80% run longer than this linear estimate.

How it works — the formula

Energy to add = Battery × (Target% − Start%)
Time = Energy ÷ Charger power
Grid energy = Energy ÷ Efficiency
Cost = Grid energy × Rate

The needed energy is a slice of the battery; time depends on charger power, and cost on the slightly larger grid draw after charging losses.

Source: U.S. DOE — Electric Vehicles

Worked examples

Example 1

60 kWh, 7.2 kW, 20→80%, 90%, $0.15

Inputs:: battery=60, power=7.2, start=20, target=80, efficiency=90, rate=0.15
Output:: 5h 0m, 36 kWh, $6.00

Example 2

75 kWh, 11 kW, 10→100%, 90%, $0.20

Inputs:: battery=75, power=11, start=10, target=100, efficiency=90, rate=0.20
Output:: ~6h 8m, 67.5 kWh, $15

Example 3

60 kWh, 150 kW DC, 20→80%, 92%, $0.40

Inputs:: battery=60, power=150, start=20, target=80, efficiency=92, rate=0.40
Output:: ~14 min (linear), ~$15.65

Limitations

Linear model; DC fast charging tapers above ~80%.
Ignores cold-weather penalties and onboard-charger limits.
Charger power may be capped by the vehicle’s acceptance rate.

Planning estimate; real charging curves are nonlinear, especially on DC fast chargers.

Frequently asked

How long does it take to charge an EV?+

Divide the energy you need to add (battery size × percentage charge) by the charger’s power. Adding 36 kWh on a 7.2 kW Level 2 charger takes about 5 hours; on a 150 kW DC fast charger, well under an hour (until it tapers near 80%).

How much does it cost to charge an EV?+

Multiply the energy drawn from the grid by your electricity rate. Adding 36 kWh to the battery at 90% efficiency draws about 40 kWh; at $0.15/kWh that is roughly $6.00. Home charging is usually far cheaper than public DC fast charging.

What is the difference between Level 1, Level 2, and DC fast charging?+

Level 1 uses a standard outlet (~1.4 kW) and is slow. Level 2 (240 V, ~7–11 kW) is typical for home and workplace charging overnight. DC fast charging (50–250 kW) bypasses the onboard charger to add range in minutes, mainly for road trips.

Why does fast charging slow down near 80%?+

To protect battery health and avoid overheating, the battery management system tapers the charging power as the pack fills, especially above ~80%. That is why charging the last 20% on a DC fast charger can take as long as the first 80%.

What is charging efficiency?+

Not all the energy drawn from the grid ends up in the battery — some is lost as heat in the charger, cables, and battery. Efficiency is typically 85–92%, so you pay for slightly more energy than the battery actually gains. This tool accounts for it in the cost.

Why charge only to 80% routinely?+

Many manufacturers recommend keeping daily charging to about 80% to prolong battery life, reserving 100% charges for long trips. Frequent full charges and deep discharges can accelerate battery degradation over the years.