Charging efficiency

Charging efficiency is stored battery energy divided by electricity drawn from the socket, multiplied by 100. The measurement boundary matters: charger-only efficiency describes a different conversion from the complete socket-to-stored-energy process. A charging estimate should say which boundary it uses.

What does the calculator assume?

The Battery Charging Cost Calculator uses a fixed 87% allowance for the complete charging estimate. This is a Riding Nexus modeling assumption, not a measured value for your scooter or a published industry average.

With that assumption, adding 470 Wh takes 470 ÷ 0.87 = about 540 Wh at the socket. About 70 Wh is outside the stored-energy total in this simplified model. That is 13% of wall input, but about 15% of stored energy. Dividing by 0.87 gives the right allowance; simply adding 13% to battery energy gives a different result.

How does this affect the price?

At an assumed $0.20/kWh, the example wall energy costs about $0.108. Charging only part of the battery reduces the estimated energy in proportion to the charge added. Actual losses depend on the equipment and session, so the fixed percentage is an approximation.

Measured socket energy already includes charging losses. If a suitable electricity monitor records 0.54 kWh, multiply that reading by your tariff directly. Dividing it by 0.87 again counts the loss allowance twice. Round-trip efficiency includes energy lost when discharging too, so it shouldn’t be substituted without checking the measurement boundary.

The energy-unit definitions come from EIA’s guide to measuring electricity. The 87% input comes from Riding Nexus’s calculator; calculations and wording were checked November 1, 2026. See the electric scooter cost per mile guide for a comparison of different efficiency assumptions.