If you are planning to buy a fuel-efficient car without range anxiety, CNG can be a cost-effective option for high-mileage city drivers with easy access to refuelling. Before making a decision, a simple monthly running cost calculation helps you understand how much you save with a Compressed Natural Gas car compared to other options.
This guide helps you to calculate your monthly running costs using a practical mileage scenario and explains how to compare them with petrol and electric running costs.
What is a Fuel Cost Calculator?
It provides you with quick estimates of how much money you will spend on fuel every month based on:
- Your per month running (km/month)
- Real-world mileage (km/kg)
- Price per kg (₹/kg)
It is useful for:
- Daily office commuters
- Taxi operators
- City users driving 1000+ km/month.
- Buyers are comparing running costs for other ICE vehicles.
CNG Monthly Fuel Expense Formula
Monthly fuel Cost(₹) = (Per Month Running in Km ÷ Mileage in km/kg) x Price (₹/kg)
Example: 1500 ÷ 22 km/kg x 78 ₹/kg = ₹5,318/month
If you drive 1500 km/month, your vehicle returns 22 km/kg, and the price is ₹78/kg:
- Fuel required = 1500 ÷ 78/kg = 68.18 kg
- Total = 68.18 x 78 = ₹5,318/month
But, a petrol variant (averaging 14 kmpl at ₹100/litre) would cost you approximately ₹10,714 to cover the same distance.
Monthly Fuel Expenses Calculator (Examples)
Here is how the common Indian usage pattern to calculate ₹/month running expenses:
Assumption used : Mileage = 22 km/kg, Gas Price = ₹78/kg
Monthly Running (KM) | CNG Needed (kg) | Expense (₹/month) |
500 | 22.73 | ₹1,773 |
750 | 34.09 | ₹2,659 |
1,000 | 45.45 | ₹3,545 |
1,250 | 56.82 | ₹4,432 |
1,500 | 68.18 | ₹5,318 |
Hatchacks often return higher km/kg, so your ₹/month may be lower.
Real-World Mileage to Use (Not ARAI)
It is the actual mileage that you get while driving in real life; owners often mistakenly calculate it based on ARAI mileage. It may also vary by vehicle type:
- Hatchbacks: 20-26 km/kg
- Compact Sedans: 22-26 km/kg
- Compact SUVs: 18-22 km/kg
Always calculate using user-tested mileage, not brochure figures.
CNG vs Petrol vs Diesel: Monthly Cost Comparison (2026)
Here is an example of how much you can save per month on fuel:
Factors | Petrol Expenses | Diesel Expenses | CNG Expenses |
Monthly Running | 1,500 km | 1,500 km | 1,500 km |
Mileage (Mixed Use) | 14 km/l | 18 km/l | 22 km/kg |
Fuel Price (Jan 2026) | ₹95 / litre | ₹88 / litre | ₹78 / kg |
Fuel Needed / Month | 107.14 litres | 83.33 litres | 68.18 kg |
Cost per km | ₹6.79/km | ₹4.89/km | ₹3.55/km |
Monthly Fuel Cost | ₹10,174 | ₹7,333 | ₹5,318 |
Monthly Savings | - | ₹2,845 | ₹4,860 |
Yearly Savings | - | ₹34,140 | ₹58,320 |
When a CNG Car Saves the Most Money?
The Compressed Natural Gas price is not the only factor for maximising your savings with a bi-fuel model in 2026. Factory-fitted variants price ₹80,000 to ₹1,20,000 more than the petrol variants. To recover it, the ideal running is 40-60 km per day and gives you the highest benefits when:
- Your running is 1,000+ km/month.
- Drives mostly in the city
- Your nearest station has a low waiting queue.
- You keep a small petrol reserve only for emergencies and to avoid anxiety about Gas running out.
Payback Period: When Does a CNG Car Become Profitable?
Monthly Usage | Yearly Savings (vs Petrol) | Time to re Recover Extra Cost |
500 km | ₹22,000 | 4.5+ Years |
1,000 km | ₹45,000 | 2 - 2.5 Years |
1,500 km | ₹68,000 | 1.2 - 1.5 Years |
2,000+ km | ₹90,000+ | Under 12 Months |
What affects the monthly fuel expense the most?
It depends on three things:
- Monthly running (km)
- Mileage in real driving (km/kg)
- Local price per kg
A small drop in mileage due to heavy traffic or AC usage can increase/decrease your spend.
How Much Petrol Should You Keep in a CNG Car?
A factory-fitted option offers two fuel options: Most bi-fuel vehicles start on petrol and switch automatically to Gas after 500 meters to 1 km when the engine reaches an ideal temperature to burn it. It can also be used as a secondary in emergencies if the gas runs out.
Who Should Buy this Option?
- If your monthly running is 1200+ km
- You drive primarily in cities.
- You Want a Middle Ground vs. EVs
- You are an Environment-conscious Commuter
Who Should Not Buy This Option?
- Not ideal for 500-700 km per month of driving; it can take 5+ years to recover the variant’s cost.
- Hilly Travel produces 10-15% less power and torque.
- Need for Boot Space- Despite the Twin Cylinder, it offers less luggage space in the boot.
- No nearby Gas Station
Top CNG Cars & Their Real-World Mileage in 2026
In 2026, Maruti Suzuki led in producing fuel-efficient vehicles, while Hyundai and Tata dominated in features. Here are the Top mileage cars and their real-world mileage.
Car Model | ARAI Mileage (km/kg) | Expected Real-World Mileage (Typical City Use) |
Maruti Suzuki Celerio | 34.43 | 28 - 30 km/kg |
Maruti Suzuki WagonR | 34.05 | 26 - 28 km/kg |
Maruti Suzuki Dzire | 33.73 | 25 - 27 km/kg |
Maruti Suzuki Swift | 32.85 | 24 - 26 km/kg |
Hyundai Exter / Aura | 27.10 | 20 - 22 km/kg |
Tata Punch | 26.99 | 19 - 21 km/kg |
Tata Nexon | 24.00 | 17 - 19 km/kg |
Every day mileage varies by load, passengers, driving style, traffic and AC usage.
FAQs
What happens if CNG runs out while driving?
Your vehicle is bi-fuel, and it automatically (or you can switch manually depending on the model) switches to petrol. That’s why keeping a 5-10 litre petrol reserve is important.
Why does my mileage change even on the same route?
Mileage can vary daily due to:
Traffic Conditions, Passenger and luggage load, Tyre Pressure, Driving style (Smooth or Aggressive), AC usage. A small change may affect your mileage daily/monthly.
Is a Factory-fitted setup better than an aftermarket kit for long-term ownership?
Yes, a factory-fitted setup is better engineered, as it meets the manufacturer's safety standards and delivers smoother performance. Aftermarket kits depend heavily on installation quality and maintenance.
What are the hidden monthly costs apart from fuel?
Apart from fuel, you may spend on periodic servicing, spark plug replacement, valve inspections and time lost in refuelling queues.
