Battery Charge Cost Calculator

Work out battery charge cost instantly with clear inputs, formula shown and shareable results.

About Battery Charge Cost Calculator

Stored energy is capacity in amp-hours times voltage, and the charger draws more than that because of conversion losses. A 5,000 mAh phone battery holds 19.3 Wh, draws about 24 Wh from the wall, and costs well under a penny to charge.

Formula

Charge cost

stored Wh = Ah x V; drawn Wh = stored / efficiency; cost = drawn kWh x tariff

Worked example

With the default values below, Battery Charge Cost Calculator returns Cost per full charge of $0.00674. Change any input above and every figure here is recalculated in your browser.

Inputs used

Battery capacity: 5,000 mAh
Battery voltage: 3.85 V
Charging efficiency: 80 %
Electricity rate: 0.28

Results

Cost per full charge: $0.00674
Energy drawn per charge: 24.06 Wh
Annual cost charging daily: $2.46
Energy stored in the battery: 19.25 Wh

Step by step

1Values used
2Charge cost
3Cost per full charge= 0.00674
4Energy drawn per charge= 24.06 Wh
5Annual cost charging daily= 2.46
6Energy stored in the battery= 19.25 Wh

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or compounding frequency into account.
Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is phone charging so cheap?

Because 24 Wh is 0.024 kWh. Charging a phone every day for a year costs around two pounds — less than a single takeaway coffee.

Where does the lost 20% go?

Heat, in the charger and in the battery itself. That is why both get warm during fast charging.