EV Charging Cost Calculator
What the wall meter reads, not just what the battery gains.
Work out EV Charging Cost. What the wall meter reads, not just what the battery gains. Built to be checked against a rating plate and a bill.
From your own bill, including per-kWh delivery charges.
Leave at zero to skip the charging time.
AC home charging is typically 0.85–0.92, worse in the cold.
Leave at zero to skip cost per mile.
Charging cost
$7.50
20% → 80% · 50.0 kWh from the wall
The battery gains 45.0 kWh but the meter reads 50.0 — 5.00 kWh goes to the onboard charger, the cables and thermal management. That gap is why a home charging bill runs above the naive battery-times-rate estimate, and it widens in cold weather when the pack has to be warmed first.
How the EV Charging Cost Calculator works
Charging is lossy. Energy drawn from the wall exceeds energy stored in the battery by roughly ten to fifteen percent on AC charging, and the meter counts the former while the dashboard reports the latter. That gap is why a home charging bill runs above the naive battery-size-times-rate estimate, and it is a parameter here rather than an omission.
Also known as: electric car charging cost · cost to charge electric car · EV cost per mile calculator · home charging cost calculator
The calculation itself
Battery capacity times the change in state of charge gives the energy the battery gains. Divide by charging efficiency for the energy drawn from the wall, then multiply by your rate.
The efficiency step is the one usually missed, and it is the reason the bill exceeds the naive estimate.
In practice
A 75 kWh battery from 20% to 80% gains 45 kWh. At 90% charging efficiency the meter reads 50 kWh — 5 kWh lost to the onboard charger, the cabling and thermal management.
At 15 cents that is $7.50. On a car doing 3.5 miles per kWh, those 45 kWh give 157 miles, so about 4.8 cents a mile.
On a 7.2 kW home charger it takes just under seven hours, which is why overnight charging on an off-peak rate is the standard pattern.
Where the losses go
The onboard charger converts AC to DC and is not perfect. Cabling has resistance. And the battery management system heats or cools the pack to keep it in its safe window, which costs energy before any charge is stored.
AC home charging typically runs 85 to 92% efficient. Cold weather is materially worse, because the pack has to be warmed before it will accept a decent rate — winter charging can lose a quarter or more.
DC rapid charging is more efficient at the vehicle but the losses move into the charger itself, and you pay a large premium for the speed regardless.
Where the figure deceives
Usable capacity is less than nominal capacity. Manufacturers reserve a buffer at both ends to protect the pack, so a 75 kWh nominal battery may have around 70 usable — which makes a percentage-based calculation slightly optimistic.
Charging also slows markedly above about 80%, so the last fifth takes disproportionately long. That is why 20 to 80 is the conventional comparison window rather than 0 to 100.
And time-of-use tariffs change the answer entirely. The same charge on a peak rate against an overnight rate can differ by a factor of three, which is the single biggest lever on running cost.
Acting on it
Compare against petrol on cost per mile rather than cost per fill — the units are what make the comparison meaningful.
Charge overnight on an off-peak tariff if one is available. It usually dominates every other efficiency consideration.
Use usable rather than nominal capacity if your manufacturer publishes it.
Frequently asked questions
How much does it cost to charge an electric car?
Battery capacity times the state-of-charge change gives the energy needed; divide by charging efficiency for what the meter reads; multiply by your rate. A 75 kWh battery from 20% to 80% needs 45 kWh, about 50 from the wall at 90% efficiency.
Why does the meter read more than the battery gains?
Losses in the onboard charger, the cables and battery thermal management. AC home charging typically runs 85 to 92% efficient, and cold weather makes it worse because the pack must be warmed.
How long does charging take?
Energy from the wall divided by the charger's power. A 7.2 kW home charger delivering 50 kWh takes about seven hours, which is why overnight charging on an off-peak tariff is the usual pattern.
Is charging at home cheaper than public charging?
Almost always, often by a factor of two or three, and more again on an off-peak overnight rate. Public rapid charging carries a large premium for the speed.
How do I work out cost per mile?
Divide the charging cost by the miles that energy provides, which comes from your car's efficiency in miles per kWh. That is the number to set against a petrol car's cost per mile.
Put this calculator on your own site
Free to use, on any site, commercial or not. Paste this where you want it to appear. It is a plain iframe, so it works in WordPress, Squarespace, Wix, Webflow, Ghost and anything else that accepts HTML.
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