Home charging · your rates

Find a lower-cost time to charge.

Add your EV’s charge need, wall power, plug-in window, and time-of-use prices. Compare an immediate start with the lowest-cost feasible start before you leave.

Plan a charging session

One charging session

Set the session and rate plan

Runs in your browser

1How much energy does the car need?

Use the vehicle’s usable battery size and current/target state of charge (SOC). Enter wall power as the maximum AC power drawn during the session—the lower of the EVSE output and vehicle’s onboard AC limit.

Usable battery capacity (kWh)Example value; check your vehicle’s documentation.

AC power drawn at the wall (kW)Use the effective session power, not just the circuit’s theoretical maximum.

Current charge (%)

Target charge (%)

Grid-to-battery efficiency (%)Planning assumption; measured efficiency varies with charger, vehicle, temperature, and SOC. Edit it if you have a better value.

2When can the car charge?

Enter the time it will be plugged in and the latest time it must be ready. If the ready-by time is earlier than the plug-in time, the window crosses midnight.

Plug-in window starts

Ready to leave by

3Enter your daily electricity rates

Example time bands are shown below—replace the sample prices with your utility’s current cents per kWh. Periods must cover all 24 hours exactly once, with no gaps or overlaps. The same schedule repeats each day.

Period	From	Until	Rate (¢/kWh)
Overnight
Day
Peak
Late night

Sample prices only: 7¢, 15¢, and 32¢ are illustrative inputs, not current utility rates. Enter your plan’s prices, including applicable per-kWh delivery charges if you want them represented.

Searches in 15-minute increments.

How it works

A custom daily-rate schedule, not a utility lookup

First, the planner estimates battery energy needed from usable capacity and the SOC change. It divides that by your efficiency assumption to estimate grid energy, then divides by wall power for a flat-power duration. For each possible 15-minute start within your plug-in window, it applies the matching rate to each minute of the session and compares total cost. If costs tie, it shows the earliest start in the window.

The rate table is user-entered and repeats every day. It does not fetch your account, identify a utility, or check whether a tariff is available in your area. Enter the applicable prices and periods from your current utility plan; the example prices are not a quote.

References

Sources and limitations

U.S. Department of Energy Alternative Fuels Data Center: Charging EVs at Home notes that residential electricity cost depends on equipment and time of day, and some utilities offer time-of-use rates.
Green Cars Compare charging calculator shows the existing session-time and per-kWh cost workflow; its page says actual results vary by weather, SOC, vehicle, and station.
Blink charging-time calculator estimates duration from battery size, charging power, and initial/target SOC.
PG&E EV Savings Calculator compares utility rate plans; rates and schedules are provider-specific.
Recurrent: EV charging losses summarizes studies showing efficiency varies by charging level, current, SOC, and temperature. The planner’s 90% value is only a user-editable example assumption.
DOE AFDC home-charging guidance recommends checking vehicle and electrical requirements and following local code; this planner does not size electrical circuits.

Good to know

Frequently asked questions

Are the sample electricity prices current rates?

No. They are example values only. Replace them with your current utility schedule and include per-kWh delivery charges if you want to estimate those components. The planner does not retrieve live tariff data.

What does “efficiency” mean here?

It is the share of electricity drawn from the grid that is estimated to reach the battery. The default is an editable illustration; real results vary by vehicle, charger, power level, state of charge, and temperature. Use a measured value when available.

Will the car always be done by the displayed time?

No. The estimate assumes steady power and does not model vehicle-specific charging curves, thermal management, preconditioning, utility interruptions, or a charging session that stops early. Check the vehicle or charger schedule before relying on it.

Does this advise how to install a charger?

No. It is not an electrical design or code-compliance tool. Have a qualified electrician assess home capacity, circuits, permits, and installation requirements.