EV charging cost calculator

Both, and they differ by exactly the charging losses. The dashboard figure counts energy leaving the battery, so 3.5 miles per kilowatt-hour; the sticker counts energy leaving the wall, so at 90% charging efficiency the same car returns 3.15 miles per metered kilowatt-hour, which is 31.7 kWh per 100 miles and prints on a label that rounds to whole units as 32. The sticker figure is the one that matches your electricity bill, and the dashboard figure is the one that matches your range.

Not in the same place, but you still pay for them. DC fast charging bypasses the on-board charger entirely and feeds the pack directly, so the conversion loss moves to the station's own equipment — and the network meters at the dispenser, on the far side of that equipment, so the price you are quoted is for energy that has already been converted. What rises instead is thermal management: fast charging heats the pack, the cooling system runs hard throughout, and that energy is billed to you and stored nowhere.

Because charging is constant-current only until the cells reach their voltage limit, after which the current has to taper to hold that voltage without damaging them. On a DC charger the practical effect is severe: the climb from 80 to 100 can take as long as the run from 20 to 80 did, which is why route planning stops at 80 and why per-minute billing punishes exactly the part of the session that delivers least. On a home circuit the taper is largely irrelevant, because the car was already limited by the on-board charger and the whole session happens overnight.

By money, if the question is what driving costs, which it almost always is. The energy comparison exists — the EPA's window-sticker methodology treats 33.7 kWh as one gallon of gasoline, from a gallon's lower heating value of about 115,000 BTU — and it produces the MPGe figure on the label. But it compares the fuels, not the machines: an internal combustion engine discards most of that gallon as heat while a motor uses most of the kilowatt-hour, so the energy equivalence flatters gasoline enormously and answers a question nobody asked at a pump.

It moves both of them, in the same direction, which is why winter surprises people twice. Consumption rises because cabin heat comes out of the same battery that moves the car and because cold air and cold tires both cost more to push through, and charging efficiency falls because the pack has to be warmed before it will accept current at any useful rate. The way to see it here is to run the page twice, once with a summer consumption figure and 90%, once with your winter figure and something lower, and take the difference as the seasonal spread rather than looking for one number that covers the year.

The buffer the manufacturer keeps back at the top and the bottom of the pack to protect its life, typically between five and ten percent of the total. It is real capacity that physically exists and that you can never charge into or draw out of, so entering the gross figure overstates every session by exactly that fraction and overstates the cost per mile by nothing at all — the miles rise with the energy, and the error hides. Use the usable figure, which is the one the range estimate was calculated from.

A few watts, continuously, and over a year that is not nothing: a unit idling at 3 W draws 26 kWh between one anniversary and the next, and a networked one with a permanent radio link draws more. It is far too small to affect any figure on this page, which prices sessions, but it is exactly the shape of load the electricity cost calculator exists to catch — a tiny draw multiplied by all 8,760 hours of the year.