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EV Charging Cost Calculator

What charging actually costs — per charge, per mile and per year — with charging losses counted.

Enter your battery size and electricity rate to see what a charge really costs.

Your car

Usable capacity, from the spec sheet.

Efficiency measured in

Real-world, from your car's trip computer. 3 to 4 mi/kWh is typical.

Electricity

From your utility bill. Off-peak overnight rates are often far lower.

Not all the electricity reaches the battery. 85–90% for Level 2 at home; lower in cold weather or on a slow Level 1 outlet.

Estimate. A real-world figure based on the assumptions listed below, which you can change.

How this calculator works

The energy that goes into your battery is the capacity times the percentage you add. But that is not what you pay for. Some of the electricity your meter records never reaches the battery: it is lost in the on-board charger, in the cables, and in keeping the pack thermally conditioned while it charges.

**Charging losses are the part almost every EV calculator omits.** Level 2 home charging typically lands around 85% to 90% efficient, and it is worse in cold weather and worse still on a slow Level 1 outlet, where the overhead runs for far longer. Dividing by efficiency is what makes the number match your electricity bill.

Cost per mile then uses your car’s real-world efficiency — the figure from its trip computer, not the EPA sticker. That is where the comparison against petrol becomes meaningful, and it is why the equivalent-MPG figure is shown: it is the fuel economy a petrol car would need to cost the same per mile.

The formula

Exactly what happens to your numbers, step by step.

  1. Energy

    into the battery = capacity × (end % − start %)
from the grid    = into the battery ÷ charging efficiency

  2. Cost

    cost per charge = grid energy × price per kWh
range added     = battery energy × miles per kWh
cost per mile   = cost per charge ÷ range added

  3. Petrol comparison

    petrol cost per mile = price per gallon ÷ MPG

A worked example

A 75 kWh battery charged from 20% to 80% at home, 15¢ per kWh, 90% charging efficiency, 3.5 mi/kWh.

What you enter

Battery
75 kWh
Charge
20% → 80%
Electricity
$0.15 per kWh
Charging efficiency
90%
Efficiency
3.5 mi/kWh

The working

Into the battery
75 × 60% = 45 kWh
Off the meter
45 ÷ 0.90 = 50 kWh
Lost to inefficiency
5 kWh
Cost
50 × $0.15 = $7.50
Range added
45 × 3.5 = 157.5 miles

$7.50 per charge — about 4.8¢ per mile

Ignoring the 5 kWh of losses would put the cost at $6.75 and understate your annual bill by 10%. At 12,000 miles a year this is about $570 of electricity, against roughly $1,440 for a 30 MPG petrol car at $3.60 a gallon.

Assumptions

Every result here rests on these. Change your inputs and the result changes with them.

  • Charging efficiency defaults to 88%, a reasonable Level 2 home figure. Level 1 and cold weather are worse; DC fast charging is often better at the vehicle but far more expensive per kWh.
  • Your electricity price is a flat rate. Time-of-use tariffs can make overnight charging much cheaper.
  • The efficiency figure is real-world, from your car rather than the sticker.
  • Battery capacity is usable capacity, which is slightly less than the headline number on some cars.

What this cannot tell you

  • Public DC fast charging usually costs two to four times the home rate and is sometimes billed by the minute; enter that rate separately to model it.
  • Battery degradation over years is not modelled.
  • It does not include the cost of installing a home charger, or any tariff standing charges.

Questions people ask

How much does it cost to charge an electric car at home?

Take your battery size, multiply by the percentage you are adding, divide by charging efficiency, and multiply by your rate per kWh. A typical 60% top-up on a 75 kWh battery at 15¢ costs about $7.50.

Why does charging use more electricity than the battery holds?

Because conversion is not free. The on-board charger, the cables and the thermal management system all consume power. You are billed at the meter, so the losses are yours to pay for — typically 10% to 15% at home.

Is charging an EV cheaper than petrol?

At home, almost always — often by a factor of two or three. Public fast charging narrows the gap considerably and can occasionally exceed petrol cost. The equivalent-MPG figure above makes the comparison directly.

Should I charge to 100%?

For daily use, most manufacturers suggest stopping around 80% for battery longevity. The last 10% to 20% is also much slower, and on a fast charger billed by the minute it is disproportionately expensive.

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Sources and review

Sources

Methodology version 1.0.0 · Last reviewed