Electric vs Petrol Running Cost Calculator
Put in what each one uses and what you pay for fuel and electricity. This gives a year of energy costs both ways, and the gap between them.
Electric saves
$762.67
- Petrol or diesel, per year
- $1,360.00
- Electric, per year
- $597.33
- Petrol per mile
- $0.11
- Electric per mile
- $0.05
- Electric is cheaper to run here, by $762.67 a year.
- This is energy only. Insurance, servicing, tax and depreciation all differ between the two and none of them are in this figure — an electric car saves on servicing and usually loses more to depreciation.
- The comparison swings hard on the electricity price. Charging at home on a night rate and charging on a motorway are different arguments entirely.
About comparing electric and petrol
This compares energy and nothing else. Over a year of ordinary mileage the electricity usually costs a fraction of the fuel, and that is the part of the argument this page can settle from four numbers.
It is not the whole argument, and the parts left out are large. Depreciation is typically the biggest single cost of running any car and differs sharply between the two. Insurance is often higher on an electric car. Servicing is generally lower, because there is no oil, no exhaust and far less brake wear. None of those can be estimated from a form without inventing figures, so none are here.
The comparison also swings hard on the electricity price, more than on anything about the cars. Charging overnight at home on a cheap rate and charging on a motorway are different arguments with different answers, and someone without off-street parking is having the second conversation whether they want to or not.
Charging losses are included on the electric side, because you pay for what the meter records rather than what reaches the battery. Leaving them out flatters the electric figure by around ten per cent.
What it works out
- Yearly energy cost, electric against petrol or diesel
- Cost per mile or kilometre for both
- Charging losses included
- Any tariff and any pump price
The formula
Petrol = Distance ÷ MPG × Price Electric = Distance ÷ 100 × kWh ÷ Efficiency × Price
Two independent sums, then a subtraction.
Over 12,000 miles the petrol car at 30 mpg burns 400 gallons, which at $3.40 is $1,360 a year — about 11 cents a mile.
The electric car uses 28 kWh per 100 miles, so 3,360 kWh reach the battery over the year. At 90% charging efficiency the meter delivers 3,733 kWh, and at $0.16 that is $597.33 — about 5 cents a mile.
The gap is $762.67 a year on these figures, which is the number worth carrying. Note how much of it rests on the two prices rather than on the cars: doubling the electricity rate to $0.32 cuts the yearly saving to $165.33, about a fifth of what it was, and that is roughly what happens to someone charging in public rather than at home.
- Distance
- Miles or kilometres a year. Two consecutive service readings will give it.
- MPG
- What the petrol or diesel car actually returns.
- kWh
- Electric consumption per 100 miles or kilometres, from the trip computer.
- Efficiency
- The share of metered energy that reaches the battery — about 90% at home.
A worked example
12,000 miles a year: a 30 mpg petrol car at $3.40 a gallon against an electric car using 28 kWh per 100 miles at $0.16.
That works out to $762.67 .
- Petrol or diesel, per year
- $1,360.00
- Electric, per year
- $597.33
- Petrol per mile
- $0.11
- Electric per mile
- $0.05
Questions
Is an electric car cheaper to run?
On energy, usually yes and often by a lot. Over 12,000 miles a 30 mpg car at $3.40 a gallon costs $1,360 in fuel, against $597.33 in electricity at $0.16 a kWh — a difference of $762.67 a year.
Does that include everything?
No. This is energy only. Depreciation, insurance, tax and servicing all differ between the two and are usually larger than the energy gap — an electric car typically saves on servicing and loses more on depreciation.
What if I cannot charge at home?
The answer changes substantially. Public charging often costs three to five times a home rate, which can erase most of the saving. Put the rate you would actually pay into the electricity field rather than a home rate you cannot use.
Why are charging losses included?
Because you are billed for what the meter records, not for what reaches the battery. Around ten per cent is lost as heat on a home charge, so leaving it out would understate the electric cost by about that much.
How does winter change the comparison?
It narrows it. An electric car loses more proportionally, because cabin heat comes from the battery rather than from waste engine heat, and cold cells are less efficient. Expect twenty to thirty per cent higher consumption in a cold month.
What about a hybrid?
Enter the economy the hybrid actually returns as the petrol figure. A hybrid sits between the two and does best in town driving, where the engine can shut down and braking energy is recovered.
Does electricity price volatility matter?
As much as fuel price volatility does, and in the same way. Both are fields here rather than published figures for exactly that reason — run the comparison again with the prices you are paying now.
How many miles before an electric car pays back?
That depends on the price difference between the two vehicles, which this page does not ask for. Divide the extra purchase cost by the yearly saving here to get a rough number of years, then set the result against how long you plan to keep it.