EV Charging Calculator
How long an EV takes to charge and what it costs, from battery size, start and target state of charge, charger power and charging efficiency.
EV Charging Calculator: with the default inputs, charging time is 6 hours, 29 minutes.
Use the usable capacity if the spec sheet gives both — that's what actually charges.
80% is the usual stopping point on a road trip — above it the charge rate collapses.
1.4 kW for a household outlet, 7.7 kW for a typical home Level 2, 150 kW+ for highway DC fast charging.
AC charging through the car's onboard charger loses 10–15% to heat; DC fast charging loses about 5%.
Home rates run 10–30¢. Public DC fast charging is often 40–60¢ per kWh.
At a constant rate — real DC fast charging tapers well before this.
- Hours
- 6.49
- Energy into the battery
- 45kWh added to the pack.
- Energy off the meter
- 50kWh you actually pay for, including charging losses.
- Cost of the session
- $8.50
- Cost per kWh in the battery
- $0.189
- Range added
- 158Miles, at the efficiency set under More options.
- Cost per mile
- $0.054
Assumptions
- Charging power is constant. This is close to true for Level 1 and Level 2 AC charging and clearly false for DC fast charging, which tapers as the pack fills.
- Efficiency covers onboard-charger and thermal losses; 90% is typical for AC and about 95% for DC.
- Cost is billed on energy drawn from the meter. Some public networks bill by the minute or add idle fees instead.
- Range added uses a flat miles-per-kWh figure; real consumption varies hugely with speed, temperature and terrain.
| Charger | kW | Time (straight-line) | Notes |
|---|---|---|---|
| Level 1 — 120 V household outlet | 1.4 | 1 day, 11 hours | 12 A on a 15 A circuit |
| Level 2 — 240 V, 30 A circuit | 5.8 | 8 hours, 37 minutes | 24 A continuous |
| Level 2 — 240 V, 40 A circuit | 7.7 | 6 hours, 29 minutes | 32 A continuous, the common home unit |
| Level 2 — 240 V, 60 A circuit | 11.5 | 4 hours, 20 minutes | 48 A continuous, needs a big feed |
| DC fast — 50 kW | 50 | 1 hour, 0 seconds | Older CCS/CHAdeMO units |
| DC fast — 150 kW | 150 | 20 minutes, 0 seconds | Typical modern highway charger |
| DC fast — 350 kW | 350 | 8 minutes, 34 seconds | Peak only, and only on 800 V cars |
DC fast times are optimistic for the reason above — the car tapers, and no car holds its peak rate for a whole session.
How this is worked out
The formula
Energy added (kWh) = battery capacity × (target% − start%) Energy drawn from the meter = energy added ÷ charging efficiency Time (hours) = energy drawn ÷ charger power (kW) Cost = energy drawn × price per kWh + session fee
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Battery capacity
- Use the usable capacity if the spec sheet gives both — that's what actually charges.from 1 to 300 · defaults to 75
- Current charge
- A number.a percentage · from 0 to 100 · defaults to 20
- Target charge
- 80% is the usual stopping point on a road trip — above it the charge rate collapses.a percentage · from 1 to 100 · defaults to 80
- Charger power
- 1.4 kW for a household outlet, 7.7 kW for a typical home Level 2, 150 kW+ for highway DC fast charging.from 0.5 to 400 · defaults to 7.7
- Charging efficiency
- AC charging through the car's onboard charger loses 10–15% to heat; DC fast charging loses about 5%.a percentage · from 50 to 100 · defaults to 90
- Electricity price
- Home rates run 10–30¢. Public DC fast charging is often 40–60¢ per kWh.in dollars · 0 or more · defaults to 0.17
- Efficiency(under More options)
- 3.5 mi/kWh is typical for a sedan; 2.2–2.8 for a large truck or SUV.from 0.5 to 10 · defaults to 3.5
- Session fee(under More options)
- Flat connection fee some public networks add per session.in dollars · 0 or more · defaults to 0
What you get back
- Charging timemain answer
- At a constant rate — real DC fast charging tapers well before this.
- Hours
- Energy into the battery
- kWh added to the pack.
- Energy off the meter
- kWh you actually pay for, including charging losses.
- Cost of the session
- Cost per kWh in the battery
- Range added
- Miles, at the efficiency set under More options.
- Cost per mile
What this assumes
- Charging power is constant. This is close to true for Level 1 and Level 2 AC charging and clearly false for DC fast charging, which tapers as the pack fills.
- Efficiency covers onboard-charger and thermal losses; 90% is typical for AC and about 95% for DC.
- Cost is billed on energy drawn from the meter. Some public networks bill by the minute or add idle fees instead.
- Range added uses a flat miles-per-kWh figure; real consumption varies hugely with speed, temperature and terrain.
About this calculator
Charging time is one division — energy divided by power — and the only complications are which energy you mean and whether the power stays constant. This calculator is explicit about both.
How to use it
Enter the usable battery capacity if your car's spec sheet distinguishes it from the gross figure; the buffer at the top and bottom of the pack never charges. Set the current and target state of charge as percentages, and the charger power in kilowatts:
- 1.4 kW — a 120 V household outlet, adding roughly 3–5 miles of range per hour.
- 5.8 to 11.5 kW — Level 2 on a 30, 40 or 60 amp circuit. The 40 A / 7.7 kW unit is the standard home installation, and adds about 25–30 miles per hour.
- 50 to 350 kW — DC fast charging. The number on the sign is the station's ceiling, not what your car will draw.
Efficiency matters because you pay for what comes off the meter, not what reaches the battery. AC charging runs through the car's onboard charger and loses 10–15% as heat; DC fast charging bypasses it and loses about 5%.
Why the DC number is optimistic
This is a linear estimate and DC fast charging is not linear. A modern EV holds near its peak rate only in a window roughly between 10% and 50% state of charge, then steps down repeatedly as the pack fills and warms, protecting the cells. By 80% most cars are pulling a third of their peak. The practical consequences:
- A session this calculator puts at 20 minutes typically takes 25–35 minutes in the real world.
- Charging 20→80% takes about as long as 80→100% on many cars, which is why road-trip advice is to stop more often and charge less each time.
- A cold pack charges far slower. Preconditioning on the way to the charger is worth several minutes.
Level 1 and Level 2 charging is essentially linear, because the car's onboard charger, not the pack, is the bottleneck. For home charging this calculator is accurate to a few minutes.
Reading the results
Energy off the meter is the billable figure. Cost per kWh in the battery is the honest price of the energy once losses are counted — at 90% efficiency, 17¢ electricity costs 18.9¢ per kWh actually stored. Range added uses the miles-per-kWh figure under More options; drop it to 2.5 or lower for a truck, in winter, or at highway speed.
Frequently asked questions
▸How long does it take to charge an EV from 20% to 80%?
On a 75 kWh battery that's 45 kWh into the pack, or 50 kWh off the meter at 90% efficiency. On a 7.7 kW home charger that's about 6 hours 30 minutes; on a 150 kW DC charger the straight-line figure is 20 minutes but expect 25–35 with the taper.
▸Why does the last 20% take so long?
Lithium-ion cells accept current fast when they're empty and slowly when they're nearly full. The battery management system steps the rate down repeatedly above about 50–60% to keep cell voltage and temperature safe. It is a chemistry limit, not a charger limit.
▸How much does it cost to charge an electric car at home?
Energy added divided by efficiency, times your rate. A 45 kWh charge at 90% efficiency draws 50 kWh; at 17¢ that's $8.50, or about 5¢ a mile at 3.5 mi/kWh — roughly a third of what the same miles cost in gasoline.
▸Should I charge to 100%?
Not routinely. Most manufacturers recommend 80–90% for daily use and 100% only before a long trip. Time spent at a high state of charge is one of the main things that ages a lithium-ion pack.
▸Why doesn't my car pull the charger's full rated power?
The station's rating is a ceiling. Your car's peak draw depends on its architecture (400 V vs 800 V), the pack temperature, the current state of charge and how many other cars share the cabinet. A 350 kW post routinely delivers 70 kW to a warm 400 V car at 60%.
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