EV Charging Cost Calculator
Enter the distance, what the car uses and what you pay per kWh. This includes charging losses, which most calculators quietly leave out.
Charging cost
$9.96
- Into the battery
- 56 kWh
- Off the meter
- 62.22 kWh
- Cost per mile
- $0.05
- Lost to charging
- $1.00
- At 90% efficiency you are billed for 62.22 kWh to put 56 kWh in the battery. The difference is heat, and you pay for it.
- Where you charge decides the answer far more than the car does. Home overnight and a motorway rapid charger can differ by four or five times per kWh.
- Cold weather costs twice: the battery is less willing to take charge, and heating the cabin comes out of the same battery.
About charging costs
Charging an electric car is priced per kilowatt hour, and the number of kilowatt hours you are billed for is not the number that ends up in the battery. Some is lost as heat in the charger, the cable and the battery itself.
The gap is around ten per cent on a typical home AC charge and can be considerably worse — a slow trickle from a domestic socket, or charging in the cold, can lose a fifth or more. Rapid DC charging is generally more efficient at the car end but the electricity costs several times as much, so it rarely comes out ahead.
That is the second and larger point: where you charge decides the cost far more than which car you drive. The same 60 kWh goes into the same battery whether it comes from a cheap overnight home rate or a motorway rapid charger, and the bill can differ by four or five times.
Consumption is entered here per hundred miles or kilometres rather than as miles per kWh, because that keeps it in the same shape as litres per 100km — linear, and safe to average.
What it works out
- Cost to cover a given distance
- Energy into the battery against energy off the meter
- What the charging losses cost
- Cost per mile or per kilometre
The formula
Energy = Distance ÷ 100 × Consumption Billed = Energy ÷ Efficiency Cost = Billed × Price
Three steps, and the middle one is the one usually skipped.
200 miles at 28 kWh per 100 miles needs 56 kWh in the battery. At 90% charging efficiency the meter has to deliver 62.22 kWh to put those 56 in, and the meter is what you are billed for. At $0.16 a kWh the charge costs $9.96, of which about $1.00 is energy that turned into heat rather than movement.
That works out at roughly 5 cents a mile. The same journey in a 30 mpg petrol car at $3.40 a gallon costs about 11 cents a mile, which is the comparison most people are actually looking for.
Efficiency is worth taking seriously as a variable rather than a constant. Home AC charging sits around 90%. A three-pin domestic socket can drop into the low eighties because the losses are fixed and the charge is slow. Cold weather is worse again, since the car spends energy warming the battery before it will accept much.
- Consumption
- kWh per 100 miles or kilometres. The trip computer will give this, usually as a running average.
- Efficiency
- How much of the metered energy reaches the battery. Around 90% at home; less on a slow charge or in the cold.
- Price
- Per kWh. Home overnight and a motorway rapid charger differ by several times.
A worked example
200 miles in a car using 28 kWh per 100 miles, charged at home for $0.16 a kWh.
That works out to $9.96 .
- Into the battery
- 56 kWh
- Off the meter
- 62.22 kWh
- Cost per mile
- $0.05
- Lost to charging
- $1.00
Questions
How much does it cost to charge an electric car?
It depends almost entirely on the tariff. Covering 200 miles at 28 kWh per 100 miles needs 56 kWh in the battery — about 62 kWh off the meter after losses — which is $9.96 at $0.16 a kWh and several times that at a rapid charger.
What are charging losses?
Energy that leaves the meter and never reaches the battery, lost as heat in the charger, cable and cells. Around ten per cent at home, more on a slow trickle or in cold weather. You are billed for it either way.
Is charging at home cheaper than a public charger?
Almost always, and usually by a wide margin. Home rates — particularly overnight tariffs — can be a quarter or less of what a motorway rapid charger costs per kWh. The car and the energy are identical; only the price changed.
How many kWh does an electric car use?
Commonly 25 to 35 kWh per 100 miles, or roughly 15 to 22 per 100 kilometres. Small cars sit at the bottom of that and large SUVs at the top, and cold weather pushes everything up.
Why does winter cost so much more?
Two things at once. The battery is less willing to accept and deliver charge when cold, and cabin heating comes from the same battery rather than from waste engine heat. A thirty per cent increase in consumption over a cold month is normal.
Is rapid charging more expensive?
Per kWh, considerably — often three to five times a home rate. It is bought for the time saved rather than the energy, which is why most owners charge at home and use rapid chargers only on long journeys.
Does rapid charging damage the battery?
Frequent rapid charging does accelerate degradation, though modern packs manage it far better than early ones. Occasional use on trips is not a concern; using it as a daily habit instead of charging at home is the case worth avoiding.
Should I charge to 100%?
Most manufacturers suggest a daily limit of 80 to 90% for lithium-ion packs and a full charge only before a long trip. Charging also slows sharply above 80%, so the last stretch takes disproportionately long on a rapid charger.