How the charging cost is worked out
The battery size and the charge window give the energy that goes into the battery. Charging losses decide how much more your home meter counts. Your car’s efficiency turns kWh into range, and from there into a cost per mile or kilometer.
Example: a 60 kWh battery charged from 20% to 80% takes in 36 kWh. With 10% losses that is 36 ÷ 0.9 = 40 kWh from the outlet, or $6.80 at $0.17 per kWh. At 3.5 miles per kWh, those 36 kWh add 126 miles of range. In kilometers, efficiency is usually given in kWh per 100 km, so the range is kWh ÷ consumption × 100.
Why charging at home is usually cheaper
At home you pay the same rate per kWh as for your fridge or your lights. A fast charger sells you the same energy plus the cost of expensive hardware, a high-power grid connection, the site and a profit margin. That is why the price per kWh at a public fast charger is often two or three times a typical home rate.
- Off-peak plans: many utilities offer cheaper night rates. Charging on a timer can lower the home cost a lot, so enter that rate.
- Subscriptions: some charging networks offer a monthly plan that lowers the price per kWh. Worth it if you fast charge often.
- Idle fees and per-minute pricing: some chargers bill by time or add a fee if you stay plugged in after charging. Check the app before you plug in.
Charging losses
No charger moves energy into a battery without losing some of it as heat. Your home meter counts everything that leaves the outlet, losses included, which is why the calculator divides by 1 minus the loss for home charging. A public fast charger bills the energy its own meter counts, so the fast charger cost here uses the energy added without the loss figure. Treat both as estimates: the real loss depends on the charger, the charging speed, the temperature of the battery and how full it is.
If your car reports efficiency from the battery, your cost per mile at home is a little higher than the trip computer suggests. Comparing a month of your electricity bill or your home charger’s app with the miles you drove gives the most honest number.
How to use the EV charging cost calculator
- 1Choose miles or kilometers, then enter your battery size or pick a rough size, and the charge level you start and stop at.
- 2Enter your home electricity rate, the fast charger price from the app and your car’s efficiency.
- 3Add how far you drive per month and, if you like, a gas car’s fuel economy and the gas price for a comparison.
Frequently asked questions
How much does it cost to charge an electric car at home?
Multiply the energy you add by your rate per kWh, and allow for charging losses. Taking a 60 kWh battery from 20% to 80% adds 36 kWh. With 10% losses the car draws about 40 kWh from the outlet, which costs $6.80 at $0.17 per kWh. The same 36 kWh at a fast charger for $0.45 per kWh costs $16.20.
Why does the calculator charge to 80% by default?
Fast charging usually slows down a lot once the battery is about 80% full, so road trip stops often end there. Many carmakers also suggest a daily charge limit below 100% for battery care. Your car’s manual says what it recommends, and you can enter any range you like.
What are charging losses?
Some energy turns into heat in the charger, the cables and the battery, so the car stores less than the meter counts. The calculator adds the loss to home charging, because your home meter counts everything. 10% is a rough starting point; slow charging from a regular outlet can lose more.
Where do I find my car’s efficiency?
Most electric cars show it in the trip computer or the app, in miles per kWh, km per kWh or kWh per 100 km. A long-term average is better than a single trip. Cold weather, high speeds and heating usually make it worse, so winter and summer figures can differ quite a bit.
Is driving electric cheaper than driving a gas car?
Often, but it depends on your prices. Charging mostly at home at a normal rate tends to beat gas by a wide margin, while charging only at fast chargers can come close to the cost of gas. Enter your own rates and your gas car’s mpg or L/100 km to see the comparison for your case.