EV tools

EV charging cost calculator

Charging cost depends on the energy that leaves the wall, not the energy that reaches the pack. This calculator keeps those two figures separate and shows both.

What does it cost to charge an EV from 20% to 80% at home?

Charging a 75 kWh pack from 20% to 80% adds 45.0 kWh to the battery, but with 10% AC charging losses the meter records 50.0 kWh. At $0.180/kWh that is $9.00, and on a 7.4 kW home charger it takes about 6.8 hours. The difference between pack energy and wall energy is what your utility bills you for.

Your inputs

Usable battery capacity

Starting charge

Target charge

Charger power

Scenario: charger

Electricity rate

AC charging loss

Site default: 10%. Energy lost between the socket and the battery pack; measured AC efficiency is typically 85–93%.

Vehicle efficiency

Driving per month

$9.00

to charge from 20% to 80%

45.0 kWh into the pack, 50.0 kWh drawn from the wall

Calculated from your inputs

Energy to pack: 45.0 kWh
Energy from wall: 50.0 kWh
Charge cost: $9.00
Charging time: 6 h 45 min

Cost per mile

$0.057

Wall energy per mile × rate, so it reflects what the meter records.

Monthly charging cost

$57.14

Based on 1,000 miles per month at 3.5 mi/kWh.

Annual charging cost

$685.71

Distance × wall energy per mile × rate, scaled to 12 average months.

Pack energy and wall energy are different numbers

Your utility bills the wall figure. The extra 10% covers the onboard charger, cable losses and battery thermal management, which is why a 75 kWh pack costs more than 75 kWh to fill.

Method

75 kWh × 60% = 45 kWh added to the pack
45 kWh ÷ 0.9 = 50 kWh drawn from the wall
50 kWh × 0.18 = 9 USD
50 kWh ÷ 7.4 kW = 6.757 hours
Wall energy per mile: 1 ÷ 3.5 mi/kWh ÷ 0.9 = 0.317 kWh/mile
0.317 kWh/mile × 0.18 = 0.057 USD/mile
1000 miles ÷ 3.5 mi/kWh ÷ 0.9 = 317.46 kWh from the wall per average month
317.46 kWh × 0.18 = 57.143 USD per average month
57.143 × 12 average months = 685.714 USD per year

Assumptions

SnapEnergyLab default: 10% AC charging loss between the wall socket and the battery pack (editable). Measured AC charging efficiency typically falls between 85% and 93%.
Charging time is an idealized estimate based on constant charger power.
Real charging may be slower because of vehicle onboard-charger limits, thermal management, battery temperature and charging taper near high state of charge.
Electricity rate of 0.18 USD/kWh (editable).
Vehicle efficiency of 3.5 mi/kWh is measured at the battery pack, so the 10% charging loss is added on top of it to get energy drawn from the wall.

What can change the result?

AC charging losses, which rise in cold weather because of battery preconditioning
Your tariff — many utilities offer much cheaper overnight EV rates
Real vehicle efficiency, which varies with speed, temperature and terrain
Whether you charge to 80% routinely or 100% occasionally
Public charging, which is usually priced well above home electricity

Home charging cost by battery size

$0.180/kWh, SnapEnergyLab default 10% AC charging loss (editable in the calculator). Wall energy is what the meter records. Generated by evEngine-1.2.0.
Battery	20→80% wall energy	20→80% cost	0→100% wall energy	0→100% cost
40 kWh pack	26.7 kWh	$4.80	44.4 kWh	$8.00
60 kWh pack	40.0 kWh	$7.20	66.7 kWh	$12.00
75 kWh pack	50.0 kWh	$9.00	83.3 kWh	$15.00
100 kWh pack	66.7 kWh	$12.00	111.1 kWh	$20.00

Where the lost energy goes

Between the socket and the cells sit the onboard charger, which converts AC to DC and gives off heat, the cable, and the vehicle’s thermal management system, which may run pumps and fans throughout the session. Together these typically consume 7–15% of the energy drawn. In freezing weather, battery heating can push that figure considerably higher, which is why winter charging appears more expensive per mile even at the same tariff.

Slow charging is not automatically more efficient. Very low-power charging from a domestic plug runs the vehicle’s auxiliary systems for many more hours, which can make its overall efficiency worse than a 7 kW wall unit despite the gentler current.

The 10% figure used above is a SnapEnergyLab default, not a universal constant. It sits in the middle of published AC charging efficiency measurements (85–93%). See Assumptions and Data sources for how site defaults are chosen, and change the value in the calculator if you have metered your own.