Fuel Savings Calculator
Compare the yearly fuel use and fuel cost of two vehicles, or two ways of driving, from their fuel consumption.
Results
Annual fuel cost difference
680.00
Vehicle B uses 400 L less fuel a year than vehicle A.
- Vehicle A cost
- 2,720.00
- Vehicle B cost
- 2,040.00
- Vehicle A fuel
- 1,600 L/yr
- Vehicle B fuel
- 1,200 L/yr
- Fuel difference
- 400 L/yr
Annual fuel cost difference 680.00. Vehicle B uses 400 L less fuel a year than vehicle A. Vehicle A costs 2,720.00 a year and vehicle B 2,040.00.
Formula
- Fuel per year (L), for each vehicle
- = annual distance (km) ÷ 100 × fuel consumption (L/100 km)
- Annual cost, for each vehicle
- = fuel per year (L) × fuel price per litre
- Fuel difference (L)
- = vehicle A fuel − vehicle B fuel
- Cost difference
- = vehicle A cost − vehicle B cost
The calculator shows the size of each difference and says which vehicle uses less fuel, so it works whichever of the two is more efficient.
Worked example
You drive 20,000 km a year. Your current car (vehicle A) uses 8 L/100 km, a car you are considering (vehicle B) uses 6 L/100 km, and fuel costs 1.70 per litre.
Step 1: Vehicle A fuel per year
20,000 ÷ 100 × 8 = 1,600 L
Step 2: Vehicle B fuel per year
20,000 ÷ 100 × 6 = 1,200 L
Step 3: Vehicle A annual cost
1,600 × 1.70 = 2,720.00
Step 4: Vehicle B annual cost
1,200 × 1.70 = 2,040.00
Step 5: Fuel difference
1,600 − 1,200 = 400 L
Step 6: Cost difference
2,720.00 − 2,040.00 = 680.00
Vehicle B would use 400 litres less fuel a year, saving 680.00 a year on fuel in whichever currency the price was given.
Compare like with like
The comparison is only fair if both consumption figures come from the same kind of source. Compare an official rating with another official rating, or your own measured consumption with a real-world figure for the other car. Comparing an official figure for one car with a measured figure for another can make either look better than it is.
Is a more efficient car worth it?
A lower fuel bill is only part of the picture. To see how long a more efficient car would take to pay for itself through fuel alone, divide the extra amount you would pay for it by the annual saving. For example, a car that costs 3,000 more but saves 600 a year on fuel takes 3,000 ÷ 600 = 5 years to make up the difference.
Purchase price, depreciation, insurance, maintenance and tax can differ between cars too, and are not included here.
Other ways to use the comparison
Vehicle A and vehicle B do not have to be different cars. You can compare your consumption before and after a change, such as driving more slowly on the motorway, removing a roof box or keeping tyres at the right pressure, as long as you measure both figures the same way.
Frequently asked questions
How do I calculate fuel savings between two cars?
Work out each car's fuel per year (annual km ÷ 100 × L/100 km) and multiply by the fuel price. The difference between the two annual costs is the saving. For example, at 20,000 km a year and 1.70 per litre, a car using 6 L/100 km costs 680 less to fuel than one using 8 L/100 km.
What if vehicle B uses more fuel than vehicle A?
The calculator still works. It shows the size of the difference and says that vehicle B uses more fuel, rather than showing a negative saving.
Which currency does the calculator use?
Any currency. Enter the fuel price in your local currency per litre, and all costs are in that same currency.
Can I compare cars with MPG figures?
This calculator uses L/100 km. Convert each US MPG figure first with the MPG to L/100 km converter, and make sure both figures use the same kind of gallon.
Does this include the cost of buying the car?
No. It compares fuel costs only. To judge whether a more efficient car is worth it, divide any extra purchase cost by the annual fuel saving to see how many years of driving it takes to recover.
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