What the Zero-Emission Vehicle Savings Calculator does
This calculator compares the running cost of an electric car with a petrol or diesel one at your own prices: energy cost per kilometre or mile for each, the yearly saving, how many years the saving takes to pay back a higher purchase price, and the tailpipe CO2 you avoid. It handles kilometres or miles, kWh per 100 km or miles per kWh, and km per litre, L/100 km or UK and US MPG.
The answer depends far more on your prices and habits than on the cars. Charging at home overnight can cost a fraction of public rapid charging, so the share of charging done at home is an input, and so are the energy losses between the socket and the battery. Nothing is assumed about electricity or fuel prices - enter what you pay.
How to use it
- Choose your currency and enter how far you drive in a year, in kilometres or miles.
- Enter the electric car's efficiency in whichever unit you have - the trip computer, a review or an official rating - and choose the unit from the list.
- Enter your home electricity price per kWh, the public charging price, and the share of charging you expect to do at home. Set charging losses to about 10% for trip-computer figures, or 0 for EPA label figures, which include losses already.
- Enter the petrol or diesel car's fuel economy and the fuel price, per litre or per gallon.
- Under "Purchase price, other costs and CO2", enter how much more the EV costs to buy, any other yearly saving such as servicing or road tax, how long you will keep it, and optionally your grid's carbon intensity.
- Read the yearly saving, the cost per kilometre or mile for each car, the payback period and the CO2 figures.
Reading the results
Cost per kilometre or mile is the fairest single comparison because it does not depend on how far you drive. Multiply by your distance to get the yearly figure.
Payback is the extra purchase price divided by the yearly saving. If it is longer than you will keep the car, the EV does not pay for itself on running costs alone at these prices.
The break-even electricity price is the blended price per kWh at which both cars cost the same to run. If most of your charging would be at rapid chargers priced near it, the running-cost advantage largely disappears.
Tailpipe CO2 is what the petrol or diesel car burns. An EV has no tailpipe, but its electricity has emissions that depend on your grid; enter a grid intensity to compare like with like.
Worked example: 12,000 km a year in India: an EV at 15 kWh/100 km against a 15 km/L petrol car
The EV needs 12,000 x 0.15 = 1,800 kWh at the battery. With 10% charging losses that is 1,800 / 0.9 = 2,000 kWh from the grid.
Charging 80% at home at Rs 8 per kWh and 20% at public chargers at Rs 20 per kWh gives a blended price of 0.8 x 8 + 0.2 x 20 = Rs 10.40, so electricity costs 2,000 x 10.40 = Rs 20,800 a year, or Rs 1.73 per km.
The petrol car uses 12,000 / 15 = 800 litres; at Rs 103 a litre that is Rs 82,400 a year, Rs 6.87 per km. The EV saves Rs 61,600 a year.
If the EV costs Rs 3,00,000 more to buy, payback takes 300,000 / 61,600 = 4.9 years, and over 8 years the net saving is Rs 1,92,800. The petrol car emits 800 x 2.348 kg = 1,878 kg of tailpipe CO2 a year.
Formulas and scoring rules
- EV energy from the grid
kWh = distance (km) x kWh per km / (1 - charging loss)- Blended electricity price
price = home share x home price + (1 - home share) x public price- Fuel used
litres = distance (km) x litres per kmkm/L: 1 / value; L/100 km: value / 100; US MPG: 3.785411784 / (value x 1.609344); UK MPG: 4.54609 / (value x 1.609344).- Payback
years = EV price premium / (fuel cost - electricity cost + other yearly saving)- Tailpipe CO2
kg = litres x 8,887 / 3.785411784 / 1,000 for petrol (2.348 kg per litre); 10,180 g per US gallon for diesel (2.689 kg per litre)US EPA combustion figures. Results are shown to the nearest unit of currency and kilogram.- EV CO2 (optional)
kg = grid kWh x grid intensity (g per kWh) / 1,000
Getting the efficiency figures right
Official EV ratings differ in what they include. US EPA ratings on fueleconomy.gov are measured from the wall socket, so charging losses are already inside them and the loss setting should be 0. The figure on the car's own trip computer is measured at the battery and excludes charging losses, which are typically around 10% on a home charger and vary with temperature and charger type. European WLTP and Indian ARAI test figures are lab cycles and usually more optimistic than real driving.
The same applies to the petrol car: a real-world figure from your own fill-ups is better than a brochure value. Winter driving, motorway speeds and air conditioning raise consumption for both kinds of car, and EVs lose proportionally more range in cold weather.
Limitations: what the result does not prove
- Prices are whatever you enter; nothing is fetched and tariffs change. Time-of-use tariffs are only approximated by the home/public split.
- It compares running and purchase costs only. Financing, insurance, resale value, battery degradation, tyre wear and home charger installation are outside the calculation unless you include them in "other yearly saving" or the purchase difference.
- CO2 covers combustion and, if entered, grid electricity. It does not include fuel production, battery and vehicle manufacture or end-of-life recycling.
- Subsidies, tax credits and road tax rules vary by country and change over time; enter the net figures that apply to you.
Privacy: where your data goes
Everything you paste, type or drop is processed in this browser tab. It is not uploaded, logged, stored or sent to analytics. Session recording and tag-manager scripts are switched off on this page.
Standards and sources
- US DOE / EPA - fueleconomy.gov vehicle efficiency figures - checked 19 Sep 2026
- US EPA - Greenhouse gas emissions from a typical passenger vehicle
- US DOE Alternative Fuels Data Center - charging electric vehicles at home
Frequently asked questions
Is an electric car cheaper to run than petrol?
Usually, if you can charge at home at a typical household price. At Rs 8 per kWh against Rs 103 per litre, an EV can cost about a quarter as much per km as a 15 km/L petrol car. If you rely on rapid public chargers the gap narrows, which is why home and public prices are separate inputs.
How do I calculate EV charging cost per km?
Multiply the car's consumption per km by your electricity price, then allow for charging losses. At 15 kWh per 100 km, 10% losses and Rs 10.40 per kWh: 0.15 / 0.9 x 10.40 = Rs 1.73 per km.
How long does it take for an EV to pay for itself?
Divide the extra purchase price by the yearly saving in running costs. A Rs 3 lakh premium recovered at Rs 61,600 a year takes about 4.9 years; a smaller premium, longer distances or higher fuel prices shorten it.
How much CO2 does a litre of petrol produce?
About 2.35 kg. The US EPA gives 8,887 g of CO2 per US gallon of gasoline, which is 2,348 g per litre, and 10,180 g per gallon of diesel, about 2,689 g per litre. These are combustion figures only.
Should I include charging losses in an EV cost calculation?
Yes, unless your efficiency figure already includes them. Energy is lost in the charger and battery, typically around 10% on home charging. EPA ratings are measured at the socket and include losses, so use 0% with those.
How do I convert miles per kWh to kWh per 100 km?
Divide 100 by the miles per kWh multiplied by 1.609344. 3.5 miles per kWh is 100 / (3.5 x 1.609344) = 17.8 kWh per 100 km. The calculator accepts either unit, so you do not need to convert by hand.
Does an electric car really have lower emissions?
It has no tailpipe emissions, and its electricity emissions depend on your grid. Enter your grid's carbon intensity to compare the two in use. Building the battery adds emissions up front, which this calculator does not include.
Last reviewed by the A2Z.Tools team against the sources listed above.
