Energy from the wall versus energy in the battery
Battery energy added is capacity multiplied by the percentage added. Grid energy is higher because charging losses occur, so divide battery energy by efficiency before multiplying by the electricity price. The model treats efficiency and the price per kWh as constant for the session.
Charging the default battery share
Seventy percent of a 60 kWh pack is 42 kWh stored. At 90 percent efficiency, the meter supplies 42 ÷ 0.90 = 46.67 kWh. At 0.25 per kWh, the session costs about 11.67. The difference, 4.67 kWh, represents the assumed charging loss.
State of charge is not a range forecast
A battery percentage says how much nominal capacity is added, not how far the car will travel. Temperature, cabin heating, speed, hills, tyres, and driving style affect energy per mile. Use the vehicle's recent consumption for a range estimate rather than treating this charge cost as a distance result.
The tariff can matter more than rounding
A home rate may change by time of use, and a public charger can add session, parking, idle, membership, or minimum charges. Those fees are not represented by a per-kWh price. Enter an all-in effective rate only when it genuinely includes the charges you expect.
Charging to a percentage is not always linear in time
The cost formula can still price the energy added, but charging power often tapers near a high state of charge. A time estimate needs charger power, the vehicle's charge curve, and any shared-stall limits; none of those are used here.
A check before comparing locations
For the same 42 kWh added, a price change from 0.25 to 0.40 per kWh changes the estimated cost from 11.67 to 18.67 at 90 percent efficiency. Compare session receipts with the battery percentage and tariff period recorded, not with a remembered headline price.
Battery capacity needs context
Usable capacity can be smaller than a brochure's gross battery figure, and a vehicle may reserve a buffer at either end of the gauge. Use the usable capacity or measured energy added for a receipt check. This calculation cannot infer that value from the vehicle name alone.
Check a receipt against the assumed loss
For the default session, 42 kWh is expected to enter the battery and 46.67 kWh to leave the meter at 90 percent efficiency. A receipt for 49.00 kWh would imply about 85.7 percent efficiency if the state-of-charge estimate and usable capacity are correct. That difference may reflect temperature, battery conditioning, vehicle auxiliaries, meter boundaries, or an inaccurate capacity assumption; it is not proof that a charger is defective. Keep the receipt, starting and ending charge, and conditions together before changing the efficiency input.
Treat time-based fees as a separate line
A per-kWh calculation gives energy cost, not necessarily the amount charged by a station. Suppose the 46.67 kWh session is priced at 0.35 per kWh: energy is 16.33. A 2.00 connection fee and a 0.10-per-minute idle charge for 15 minutes make the receipt 19.83. Adding those charges after the energy calculation keeps their basis visible. Entering 0.425 as a fictional energy tariff may reproduce one receipt but will fail when the session length or fixed fee changes.
Battery percentage is not an energy bill by itself
The same displayed 70 percent can mean different kWh on different usable capacities. A 50 kWh usable pack gains 35 kWh; a 75 kWh usable pack gains 52.5 kWh. At 90 percent efficiency, those require 38.89 and 58.33 kWh from the grid. Confirm whether the manufacturer publishes usable rather than gross capacity, and update the input if a measured session gives a better practical basis. The calculation prices declared energy; it cannot diagnose degradation, forecast range, or certify equipment safety.
Keep the charging boundary visible
For each comparison, note whether energy came from a home meter, a public-station receipt, or the vehicle's battery display. Those instruments sit on different sides of charging losses, so their kWh values need not match. Record the tariff period, fixed fees, start and end state of charge, and whether cabin preconditioning occurred. A result becomes more reliable when it is revised from several comparable sessions rather than one unusually cold or fast charge. Do not use the cost output as a statement about electrical installation suitability, battery health, charging time, or available driving range; those questions require additional measurements and manufacturer guidance.
Auto tools
All auto calculators · Tire Size Calculator · Tire Size Comparison
It is informational only and is not medical or professional advice.