Monthly EV Charging Cost Calculator

Home vs public charging

The gap between charging at home and charging on a DC fast charger is bigger than most new owners expect. US home electricity averages around $0.13 per kWh; public fast chargers usually land between $0.30 and $0.50. At 3.5 miles per kWh that works out to roughly 4 cents a mile at home and 9 to 14 cents on the road. Same car, same miles, triple the cost.

Calculating monthly cost

Total energy = monthly miles ÷ efficiency (miles per kWh)

Home cost = total kWh × home share × home rate

Public cost = total kWh × public share × public rate

Most EVs manage 3 to 4 miles per kWh in mixed driving. Sustained highway speed drops that to 2.5 to 3, since aerodynamic drag rises with the square of speed and there is no regenerative braking to recover anything. Stop-start city driving is where EVs shine, often 4 to 5 miles per kWh.

A note on charging losses

Roughly 10 to 15% of the energy that leaves your meter never reaches the battery. It is lost as heat in the on-board charger and cables during AC charging, and it is real money: your utility bills the wall, not the pack.

This matters for which efficiency number you type in. The miles-per-kWh figure on the car’s trip screen is measured at the battery, so it does not include that loss. If you use it, expect the real bill to run about 10% above the answer here. To capture the loss, either divide your trip-meter figure by 1.1 before entering it, or work out your own number by dividing miles driven by the kWh your charger reports having delivered.

Comparing to petrol

A 30 MPG car at $3.50 a gallon costs $11.67 per 100 miles. At $0.13/kWh and 3.5 miles/kWh the EV costs $3.71 for the same distance, about a third. Charge that same car exclusively at $0.40/kWh public rates and it costs $11.43 per 100 miles, which is a rounding error away from the petrol car. Home charging is not a nice-to-have in the EV cost argument. It is the entire argument.