Fuel Cost Per Kilometre: How to Compare Petrol, Hybrid, and Electric
When people compare cars, they usually start with the purchase price. Fair enough. That number is large and rude and hard to ignore.
But if you actually drive the thing a lot, the running cost matters just as much. A car that is cheap to buy but thirsty every week can quietly turn into a wallet pickpocket. A pricier hybrid or EV can look fancy until you realise the real question is simpler: what does it cost per kilometre?
That is the number that lets you compare petrol, hybrid and electric cars without getting lost in marketing fluff, dealership optimism, or your mate insisting his ute is somehow "not that bad on fuel".
The basic formula
For petrol or diesel cars, the formula is:
Fuel cost per kilometre = (L/100km × fuel price per litre) ÷ 100
For EVs, it becomes:
Electricity cost per kilometre = (kWh/100km × electricity price per kWh) ÷ 100
That is it. No wizardry. No spreadsheet with 14 tabs. Just consumption multiplied by unit price.
A simple Australia-friendly example
Let us compare three cars using scenario numbers for illustration, not national averages:
- Petrol car: 8.5L/100km at $2.00/L
- Hybrid: 4.5L/100km at $2.00/L
- EV: 16kWh/100km at $0.30/kWh home charging
Petrol: 8.5 × 2.00 ÷ 100 = $0.17/km
Hybrid: 4.5 × 2.00 ÷ 100 = $0.09/km
EV: 16 × 0.30 ÷ 100 = $0.048/km
In plain English, that is about:
- 17 cents/km for the petrol car
- 9 cents/km for the hybrid
- 4.8 cents/km for the EV on home charging
That gap gets interesting fast once you drive real distances.
What that means over a year
Say you drive 15,000 km a year. That is a useful illustration for someone with a regular commute, even though your actual number could be much lower or higher.
- Petrol: 15,000 × $0.17 = $2,550 a year
- Hybrid: 15,000 × $0.09 = $1,350 a year
- EV: 15,000 × $0.048 = $720 a year
Compared with the petrol car in this example, the hybrid saves about $1,200 a year in energy cost and the EV saves about $1,830 a year.
That does not automatically mean the EV is the best financial choice. It just means the energy cost is lower. The purchase price still gets a vote, unfortunately.
If you want the real answer for your own driving, plug your distance, fuel use and price into the Fuel Cost Calculator. Guessing usually makes efficient cars look less efficient and inefficient cars look weirdly "not too bad".
Where hybrids usually shine
Hybrids often look strongest in city driving because stop-start traffic is where regular petrol cars waste fuel like it is a hobby. That is also why somebody's official combined figure can look decent on paper, while their real-world suburban school-run number is quietly horrific.
If your driving is mostly suburban, traffic-heavy, or full of short trips, a hybrid can be a very sensible middle ground. You avoid the higher fuel burn of a normal petrol car, but you also avoid having to think about home charging, public charger pricing, or whether the only fast charger on your route is currently occupied by someone treating 92 percent battery like an emergency.
Where EV maths can get messy
EVs are often cheapest per kilometre if you mostly charge at home. That bit matters.
If you rely heavily on public fast charging, the running cost can rise a lot. For example:
EV on fast charging: 16kWh/100km at $0.60/kWh = 9.6 cents/km
That is still competitive with many petrol cars, but suddenly it is much closer to hybrid territory.
So when somebody says EVs cost almost nothing to run, the honest answer is: sometimes yes, sometimes calm down. Charging setup matters. Tariff matters. Driving style matters. Even winter and highway speeds can shift the numbers.
What fuel cost per kilometre does not include
This is the bit people skip when they are halfway to convincing themselves a car is a bargain.
Per-kilometre energy cost only tells you what it costs to keep the car moving. It does not include:
- purchase price
- interest or finance costs
- registration and insurance
- servicing, tyres and repairs
- depreciation
That is why a car can be cheap per kilometre and still be expensive overall. An EV with low charging costs can still be a terrible deal if you overpay for the car or finance it badly. A cheap used petrol hatch can still win if the upfront price gap is massive and you barely drive.
How to compare properly before you buy
If you are choosing between petrol, hybrid and electric, compare them in this order:
- Cost per kilometre based on your real usage
- Annual distance because savings only matter if you drive enough to capture them
- Purchase price gap between the cars you are actually considering
- Finance structure if you are borrowing or salary packaging
- Practical stuff like charging access, boot space, family use, and reliability
That last point matters more than people admit. The cheapest car on paper is not always the best one if it does not fit how you live. Saving money is good. Resenting your car every day is less ideal.
Quick break-even thinking
Here is a simple way to think about it.
If a hybrid saves you $1,200 a year in fuel compared with a petrol car, but costs $4,000 more to buy, the rough fuel-only break-even is about 3.3 years.
If an EV saves you $1,830 a year in charging versus petrol, but costs $10,000 more upfront, the rough energy-only break-even is about 5.5 years.
That is not a full ownership analysis, but it is a useful first filter. If you know you will sell the car in two years, a long break-even period matters. If you keep cars forever and drive heaps, it matters less.
When finance changes the answer
Sometimes the running-cost winner loses once finance enters the chat.
If a more efficient car means a much bigger loan, the monthly repayment can swallow the fuel saving. That is why it is worth modelling the purchase with the Car Finance Calculator instead of just staring at cents per kilometre and declaring victory.
If you are an employee looking at salary packaging, the Novated Lease Calculator can also help. In some cases, especially for eligible battery EVs and hydrogen fuel-cell vehicles, the packaging structure can shift the maths quite a bit. In other cases, it mostly shifts the brochure enthusiasm.
Important: plug-in hybrid treatment changed after 1 April 2025, so do not assume every electrified vehicle gets the same Fringe Benefits Tax treatment. If that tax angle matters to your decision, check the latest ATO rules before signing anything.
The practical rule of thumb
- Low annual kilometres: upfront price matters more than tiny running-cost differences
- Medium annual kilometres: hybrids often look very sensible
- High annual kilometres with easy home charging: EVs can look extremely strong
- Heavy fast-charger reliance: do the maths carefully before assuming EV equals cheapest
The bottom line
Fuel cost per kilometre is one of the cleanest ways to compare petrol, hybrid and electric cars because it strips the conversation back to something measurable. No vibes, no fan clubs, just maths.
For a lot of Australians, the rough pattern is simple: petrol usually costs the most per kilometre, hybrids usually land in the middle, and EVs are often cheapest if home charging is part of the setup.
But do not stop at running cost alone. Compare the purchase price, the finance cost, and how the car fits your life. A cheaper kilometre is great. A smarter overall decision is better.
Frequently asked questions
How do I calculate fuel cost per kilometre?
Multiply litres per 100km by the fuel price per litre, then divide by 100. For EVs, use kWh per 100km multiplied by electricity price per kWh, divided by 100.
Are hybrids always cheaper to run than petrol cars?
Usually in everyday city driving, yes. But the real answer depends on the specific car, your driving pattern and current fuel prices.
Are EVs always the cheapest per kilometre?
Often when charged mostly at home. If you depend heavily on expensive public fast charging, the gap can narrow a lot.
Does cost per kilometre include servicing and depreciation?
No. It only covers the energy side of running the car. You still need to factor in purchase price, finance, servicing, tyres, insurance, registration and depreciation.
Start with the Fuel Cost Calculator, then model the buying side with Car Finance or Novated Lease if salary packaging is on the table.
Notes: Worked examples in this article use scenario assumptions for illustration. Real-world fuel economy, charging efficiency, tariffs, traffic, weather and driving style can all change your actual cost per kilometre.