Which fuel is cheapest to run in India?
Petrol, CNG and electric cars are all sold on the same forecourts now, and the newest petrol you buy is almost certainly E20 — a 20% ethanol blend. But the sticker price of a litre, a kilogram or a kilowatt-hour tells you nothing on its own: what matters is the running cost per kilometre, which depends on how far each fuel actually carries your car. This comparator puts petrol, E20, CNG and EV on the same ₹/km scale so you can see which one is cheapest to drive at today’s prices — and how much that adds up to over a month and a year.
It is a running-cost comparison only. It answers “which fuel is cheapest to drive per km”, not the full total cost of owning the car — see the assumptions below.
How the cost per km is calculated
Every fuel uses the same simple idea: take the price of one unit of energy and divide by the distance that unit carries you. The energy unit cancels, leaving pure rupees per kilometre — which is exactly what makes the four fuels directly comparable:
costPerKmPetrol = petrolPrice (₹/L) ÷ mileagePetrol (km/L) costPerKmE20 = petrolPrice (₹/L) ÷ [ mileagePetrol × (1 − drop%/100) ] costPerKmCng = cngPrice (₹/kg) ÷ mileageCng (km/kg) costPerKmEv = evTariff (₹/kWh) ÷ efficiencyEv (km/kWh) monthlyCost = costPerKm × monthlyKm annualCost = monthlyCost × 12
The unit that trips everyone up is CNG. Petrol and E20 are dispensed and priced per litre, and electricity per kilowatt-hour — but CNG is a compressed gas, so it is metered by mass and priced per kilogram (₹/kg), not per litre. Your CNG mileage is therefore in km/kg, and ₹/kg ÷ km/kg still cancels cleanly to ₹/km. Entering a CNG price as if it were per litre is the single most common way to get this comparison wrong.
E20 is the other subtlety: it is pumped at the same per-litre price as petrol, but because ethanol carries only about 65% of petrol’s volumetric energy (IEA-AMF), a litre of E20 takes you slightly less far. The calculator applies a mileage penalty (default 3.5%, per MoPNG) to petrol economy, so E20 always costs a touch more per km than pure petrol at the same pump price. To model that efficiency penalty on its own — extra litres and extra rupees per month for your specific car — use the dedicated E20 mileage impact calculator, which turns the efficiency drop into your monthly extra fuel cost.
Worked example
These figures are generated by the same engine that powers the calculator above.
With petrol at ₹100.00/L (18 km/L), CNG at ₹80.00/kg (22 km/kg), electricity at ₹8.00/kWh (7 km/kWh) and a 3.5% E20 penalty, driving 1,000 km a month works out as follows:
| Fuel | Cost / km | Per month | Per year |
|---|---|---|---|
| Petrol | ₹5.56/km | ₹5,555.56 | ₹66,666.67 |
| E20 | ₹5.76/km | ₹5,757.05 | ₹69,084.63 |
| CNG | ₹3.64/km | ₹3,636.36 | ₹43,636.36 |
| EV | ₹1.14/km | ₹1,142.86 | ₹13,714.29 |
The cheapest to run is EV at ₹1.14/km — about ₹52,952.38 a year less than petrol at this driving distance.
Typical Indian assumptions
The defaults below reflect a mid-size hatchback at broadly representative 2025 Indian prices. Every one is editable — prices in particular vary sharply by city and state, so replace them with your local figures.
| Fuel | Priced | Typical price | Default economy | Source |
|---|---|---|---|---|
| Petrol | per litre (₹/L) | ~₹100/L | 18 km/L | PPAC (MoPNG) |
| E20 (20% ethanol) | per litre (₹/L) | same as petrol | 3–3.5% lower km/L | MoPNG / ARAI |
| CNG | per kilogram (₹/kg) | ~₹80/kg | 22 km/kg | PNGRB |
| EV | per kilowatt-hour (₹/kWh) | ~₹8/kWh | 7 km/kWh | DISCOM slabs / LBNL |
Assumptions and limitations
- Running cost only. This excludes the vehicle purchase price, a CNG retrofit kit, EV or home-charger installation, insurance, servicing, tyres, battery replacement, road tax and depreciation. A fuel that is cheaper per km can still have a higher total cost of ownership.
- Flat prices. Each fuel is charged at the single rate you enter — no tiered electricity slabs, time-of-use tariffs, fixed monthly charges or fast-charger premiums unless you bake them into the tariff yourself.
- The E20 penalty is a modelled average. Actual mileage loss depends on whether your car is E10-only, E10-compatible or E20-calibrated, plus driving style, load and traffic. ARAI reports a 2–6% fleet range. The penalty stems from ethanol's lower energy density — you can see the exact ethanol-to-petrol ratio and energy content of any blend behind that figure.
- Prices are illustrative, not a live feed. Fuel, CNG and electricity prices are volatile and differ widely by location. Verify current local prices before making a purchase decision.
- Not purchase or investment advice. Treat the output as an estimate of running cost to inform, not replace, your own judgement.
Frequently asked questions
Which fuel is cheapest in India in 2025 — petrol, CNG or EV?+
At typical Indian prices (petrol ~₹100/L, CNG ~₹80/kg, electricity ~₹8/kWh) and average hatchback economy, EV works out to roughly ₹1.14/km, CNG around ₹3.64/km, E20 petrol about ₹5.76/km and pure petrol approximately ₹5.56/km. EV is the cheapest to run per km by a wide margin at most cities' domestic electricity tariffs, though fuel prices vary significantly by state. Enter your local prices for a personalised comparison.
Is EV cheaper than petrol per km in India?+
Yes, in virtually all scenarios at current prices. An EV running on domestic electricity at ₹8/kWh and achieving 7 km/kWh costs about ₹1.14/km — roughly one-fifth the per-km running cost of a petrol car doing 18 km/L at ₹100/L (≈₹5.56/km). Even at premium public fast-charger tariffs of ₹15–20/kWh the EV still undercuts petrol. The gap narrows if electricity tariffs are high or the car is inefficient.
What is the running cost of a CNG car per km?+
CNG cost per km depends on your city's CNG price (in Rs/kg — CNG is priced by the kilogram, not the litre) and your car's mileage in km/kg. At ₹80/kg and 22 km/kg a typical hatchback costs about ₹3.64/km. CNG is 30–35% cheaper per km than petrol at prevailing Indian prices, though CNG availability and prices vary widely: Delhi is around ₹83/kg while some southern cities charge ₹97–109/kg.
How much more does E20 cost per km than petrol?+
E20 (20% ethanol blend) costs slightly more per km than pure petrol at the same pump price because ethanol has a lower volumetric energy content — around 65% that of petrol (IEA-AMF). A 3.5% mileage drop (per MoPNG) on a car doing 18 km/L raises the effective cost from ₹5.56/km on petrol to ₹5.76/km on E20. ARAI testing has found the drop can range from 2% to 6% depending on the vehicle model and age.
How do I calculate fuel cost per km?+
Fuel cost per km is price per unit of fuel divided by the distance covered per unit: Cost/km = Fuel price ÷ Mileage. For petrol: ₹100/L ÷ 18 km/L = ₹5.56/km. For CNG: ₹80/kg ÷ 22 km/kg = ₹3.64/km. For EV: ₹8/kWh ÷ 7 km/kWh = ₹1.14/km. The energy unit (litre, kilogram, kilowatt-hour) cancels, leaving rupees per kilometre — the fuels are then directly comparable.
Is CNG cheaper than EV per km?+
At typical Indian prices, no — EV is cheaper. EV running cost is roughly ₹1.14/km versus CNG at ₹3.64/km at the defaults used here. However, in cities with very high electricity tariffs (above ₹15–18/kWh at public fast-chargers) or for EV models with poor efficiency, the gap narrows. Use this calculator with your actual electricity tariff and EV km/kWh figure to compare directly.
What is the difference between petrol and CNG cost per km?+
At typical Indian prices, CNG is roughly 35% cheaper per km than petrol. A petrol hatchback doing 18 km/L at ₹100/L costs about ₹5.56/km; a CNG car doing 22 km/kg at ₹80/kg costs about ₹3.64/km — a saving of about ₹1.92/km. At 1,000 km/month that adds up to roughly ₹23,000 per year. CNG prices in some southern cities are significantly higher than Delhi, so the saving varies by location.
Does E20 fuel increase my monthly running cost?+
Yes, slightly. Because E20 contains 20% ethanol, which has lower volumetric energy content than petrol, your fuel economy drops by around 3–3.5% (MoPNG) or up to 6% (ARAI) compared with E10/petrol at the same pump price. At a 3.5% drop, the cost per km rises from ₹5.56 to ₹5.76 — an increase of about ₹200 per month at 1,000 km driving. For E20-calibrated vehicles (newer models designed for the blend) the impact is at the lower end, 1–2%.
Why is CNG priced per kg and not per litre?+
Natural gas is a gas at ambient conditions and is compressed for storage (hence Compressed Natural Gas). Because its volume changes dramatically with pressure and temperature, dispensers measure CNG by mass — kilograms — rather than volume. This is why PNGRB (the Indian gas regulator) publishes and regulates CNG prices in rupees per kilogram, and why vehicle economy for CNG is expressed in km/kg, not km/litre.
Does this calculator include vehicle purchase cost or maintenance?+
No — it is a running-cost (fuel and energy) comparator only. It does not include vehicle purchase price, the cost of a CNG retrofit kit (~₹50,000–80,000), EV home-charger installation, insurance premiums, servicing, tyre replacement or resale value. Those factors matter for total cost of ownership, but this calculator answers the focused question: which fuel is cheapest to drive per km at today's prices.
What EV efficiency (km/kWh) should I use?+
For Indian 4-wheeler EVs, Lawrence Berkeley National Laboratory data shows city driving at roughly 84–123 Wh/km (about 8–12 km/kWh) and highway at 133–165 Wh/km (about 6–8 km/kWh). The default of 7 km/kWh is a conservative blended real-world figure. Popular models vary: a compact electric hatchback might achieve 8–10 km/kWh in city driving, while a larger SUV-EV might return 5–6 km/kWh on the highway. Use your car's real-world figure if you know it.
How does the cheapest fuel change if CNG prices rise?+
The break-even point between CNG and petrol shifts as prices change. If CNG rises from ₹80/kg to ₹95/kg while petrol stays at ₹100/L, CNG cost per km goes from ₹3.64 to ₹4.32 — still cheaper than petrol at ₹5.56/km but the gap narrows by about one-third. EV at ₹1.14/km remains comfortably cheapest. Enter the current prices in your city to see where the break-even sits for your driving profile.
Disclaimer
Sources
- PPAC (MoPNG) — Retail Selling Price of Petrol and Diesel (per litre)
- PNGRB — CNG retail prices (per kilogram)
- IEA-AMF — Ethanol fuel properties (energy content, volumetric heating value)
- LBNL — Electrical consumption of light-duty EVs in India (km/kWh benchmarks)
- Business Standard — E20 mileage impact limited to 3–3.5% (MoPNG/Maruti Suzuki)
Formula and data last reviewed by the TheCalculatorVault team on 5 July 2026. Figures are for general information, not professional advice.
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