How to use this calculator
An EV's dashboard efficiency describes energy reaching the battery, while the utility meter also sees charging losses. This calculator separates the two so the bill estimate reflects energy drawn from the wall.
- Enter monthly home-charged miles.
- Use observed kWh per 100 miles.
- Include charging loss and your home rate.
FORMULA
The math behind the estimate
miles × kWh per 100 miles ÷ 100 = battery energy. Divide by charging efficiency for grid energy, then multiply by rate.
Worked example
Driving 1,000 miles at 30 kWh/100 miles with 10% losses requires about 333 grid kWh and costs about $60 at $0.18/kWh.
Change the defaults to model your home. The result is an estimate, not a guaranteed bill or savings promise.
How to read the result
Use the estimate to compare scenarios and find the inputs worth measuring more carefully. Utility bills can include fixed charges, taxes, delivery fees, minimums, tiers, and demand charges that are not fully represented by a simple energy rate.
Assumptions and limitations
- All entered miles are charged at home.
- Losses include charger and battery conditioning.
- Public charging and subscription fees are excluded.
Climate, equipment condition, installation, controls, and household behavior can materially change results. Verify consequential installation and purchasing decisions with qualified providers.
Practical savings context
Schedule charging in the lowest-rate window when supported. Compare the full tariff, not just the cheapest advertised rate.
SOURCE
Data and methodology
U.S. Department of Energy — Electric Vehicles
Guidance accessed August 2026. Geographic scope: United States. Last reviewed: August 6, 2026.
WattMeasure uses the source to frame the method and assumptions; your editable inputs determine the displayed result.
QUESTIONS
EV charging FAQ
How accurate is this EV charging estimate?
It is a planning estimate based on the values you enter. Actual power draw, cycling, utility charges, climate, and equipment condition can change the result.
Should I use the default electricity rate?
Your own marginal or all-in supply rate is better. Check a recent bill or your utility's published rate schedule.
Does this include taxes and utility fees?
Only when they are reflected in the rate you enter. Fixed monthly charges are not included because they usually do not change with one appliance's usage.
Last reviewed August 6, 2026 · Data update policy