EV vs Petrol Calculator by Mileage: Worked Example With Stated Assumptions

The question behind ev vs petrol calculator by mileage is really two smaller questions: what does each car use per mile, and what does that energy cost where you buy it. Answer those two and the comparison is arithmetic. This page answers them in order, states the assumptions openly, and then shows the result at several annual mileages so you can see how the answer scales. Where the page leaves something out — purchase price, depreciation, insurance, servicing and tax — it says so by name.

The short answer is that the comparison comes down to cost per mile: the petrol car burns US gallons, so its cost per mile is the price per gallon divided by its MPG, while the EV uses kilowatt-hours, so its cost per mile is the electricity price per kWh divided by its miles per kWh. With the example assumptions on this page — petrol at $3.45 per US gallon, 35 US MPG, electricity at 25 cents per kWh and 3.8 miles per kWh — the petrol car costs about $0.10 per mile and the EV about $0.07 per mile. Those are example figures, not prices you should quote, and the rest of this page shows how they were reached and what would change them.

ev vs petrol calculator by mileage: Assumptions used on this page

Taking ev vs petrol calculator by mileage as the case in point: Every figure in the tables below comes from this assumptions table. Each one is an assumption or an example, not a measured fact about any particular car or a current price. Substitute your own numbers and the method still works.

Input Value used Status
Petrol price $3.45 per US gallon Example price
Petrol efficiency 35 US MPG Assumption
Electricity price 25 cents per kWh Example price
EV efficiency 3.8 miles per kWh Assumption
Annual mileage 12,000 miles Example

ev vs petrol calculator by mileage: How the EV versus petrol comparison works

For ev vs petrol calculator by mileage, the point is this: Hold the mileage constant and price the energy each car actually uses. For the petrol car, cost per mile equals the price per gallon divided by its MPG. For the EV, cost per mile equals the price per kWh divided by its miles per kWh. Multiply each cost per mile by the annual mileage and you have the annual fuel and charging bill for each car; subtract one from the other and you have the saving, or the extra cost, under those assumptions. The method is deliberately simple, because a simple method with honest inputs beats a complicated model built on guessed ones. The two numbers that matter most are the electricity price and the petrol car's MPG: a driver who charges at home on a cheap overnight rate will see a very different answer from a driver who relies on public rapid chargers, and a thirsty petrol car widens the gap while an efficient one narrows it.

ev vs petrol calculator by mileage: Worked example: the same distance, two energy bills

Take a driver covering 12,000 miles a year. The petrol car does 35 MPG and petrol costs $3.45 per gallon as an example price, so its cost per mile is $3.45 ÷ 35 = $0.10, and 12,000 miles cost $1,182.86 a year. The EV does 3.8 miles per kWh and electricity costs 25 cents per kWh as an example price, so its cost per mile is $0.25 ÷ 3.8 = $0.07, and 12,000 miles cost $789.47 a year. The difference on fuel and charging alone is $393.38 a year in the EV’s favour under these assumptions. Now change one input and watch the answer move: if the EV is charged mostly at a public rapid charger at, say, double the home electricity price used here, its annual charging cost doubles and most of the saving disappears. If the petrol car is driven mainly in town at lower MPG, the petrol bill rises and the saving grows. That sensitivity is the real lesson — the answer is only as solid as the assumptions, so write yours down before you believe the result.

Cost at different annual mileages for ev vs petrol calculator by mileage

The table uses the worked-example assumptions above — petrol at $3.45 per gallon (example), 35 MPG, electricity at 25 cents per kWh (example), 3.8 miles per kWh. The gap grows with mileage, which is why high-mileage drivers see the biggest fuel-cost difference and low-mileage drivers see the smallest.

Annual miles Petrol cost per year EV charging cost per year Difference
6,000 $591.43 $394.74 $196.69
8,000 $788.57 $526.32 $262.26
10,000 $985.71 $657.89 $327.82
12,000 $1,182.86 $789.47 $393.38
15,000 $1,478.57 $986.84 $491.73
20,000 $1,971.43 $1,315.79 $655.64

ev vs petrol calculator by mileage: Cost per mile and per 100 miles

At the example assumptions, the petrol car costs $0.10 per mile ($9.86 per 100 miles) and the EV costs $0.07 per mile ($6.58 per 100 miles). Per 100 miles is often the easier figure to compare with a fuel receipt or a charging bill, because both are usually priced in round numbers per hundred miles of driving. If you know your own MPG and your own prices, the same two divisions give your own figures: fuel price per gallon divided by MPG, and electricity price per kWh divided by miles per kWh.

Comparing by car or by mileage for ev vs petrol calculator by mileage

For ev vs petrol calculator by mileage, the point is this: The only fair comparison holds the mileage constant and uses each car's own efficiency. Comparing two cars over different mileages, or comparing one car's best-case efficiency with another's worst case, tells you nothing. Pick a mileage you actually drive, use each car's realistic efficiency — not its brochure figure — and price the energy at the rate you actually pay. If you are comparing specific models, do the same sum for each one separately and compare the totals, rather than trusting a single headline saving that may have been calculated at a mileage you will never drive.

ev vs petrol calculator by mileage: What the comparison leaves out — and why it matters

Before treating any EV saving as a promise, check what was excluded. This page's maths covers fuel and charging only. It does not include the price difference between the cars, depreciation, insurance, servicing, tyres, or tax — all of which differ between an EV and a petrol car and all of which change the real answer. It also assumes a single electricity price, while real charging mixes cheap home charging with expensive public rapid charging, and the mix matters more than the headline rate. A driver who charges at home overnight will beat the figures here; a driver who relies on rapid chargers may not. Work out your own mix, price it honestly, and only then compare the totals. That is the point this page works through for ev vs petrol calculator by mileage.

Common mistakes for ev vs petrol calculator by mileage

  • On this page, ev vs petrol calculator by mileage is the case in point: Forgetting charging losses is another: slightly more electricity is drawn from the plug than the battery stores, so dividing the battery size by the miles driven understates the real cost per mile by a few percent.
  • For ev vs petrol calculator by mileage, the point is this: Using the same electricity price for every charge hides the real cost. A driver who mixes home and public charging has two different prices, and averaging them into one number without weighting by how much energy comes from each is a common error.
  • Taking ev vs petrol calculator by mileage as the case in point: Forgetting that winter changes EV efficiency is easy to miss. Cold weather reduces an EV's miles per kWh noticeably, so a saving calculated on summer figures will overstate the winter result.
  • On this page, ev vs petrol calculator by mileage is the case in point: Using one tank or one charge instead of an average is next — a single fill is noisy, and a pump that clicks off early can add a phantom gallon, while a single charge says nothing about your usual mix of home and public charging.

ev vs petrol calculator by mileage: Related calculations

These pages continue from here: the same method on a neighbouring question, or the calculator that runs the arithmetic for you. That is the point this page works through for ev vs petrol calculator by mileage.

Putting your figure to work for ev vs petrol calculator by mileage

Taking ev vs petrol calculator by mileage as the case in point: Putting the figure to work is where the method pays off. Once you know your own cost per mile for each car, measured with your own prices and efficiencies, you can price any journey before you set off and compare cars honestly, because you are comparing measured figures rather than brochure claims. Keep a simple log — date, miles, energy used, price paid — and review it monthly. Patterns show up quickly: a winter dip in EV efficiency, a motorway improvement, a slow rise in your charging cost that points to more public charging than you planned. The log turns a vague feeling about fuel use into a number you can act on, and that is the whole point of measuring in the first place.

Frequently asked questions

Does an EV cost more to insure?

For ev vs petrol calculator by mileage, the point is this: Insurance is not part of the fuel-and-charging maths on this page, and it can differ between an EV and a petrol car for reasons that have nothing to do with energy: repair costs, parts availability and the car's value all play a part. Get a quote for both cars before comparing total costs.

Is an EV always cheaper to run than a petrol car?

For ev vs petrol calculator by mileage, the point is this: Not always. On fuel and charging alone, an EV is usually cheaper per mile when it charges mostly at home at an example electricity price, but the answer flips if it relies on expensive public rapid charging or if the petrol car is very efficient. Purchase price, depreciation, insurance and servicing are not in the fuel-cost maths, so a full comparison has to include them before calling either car cheaper overall.

How many kWh does it take to charge an EV?

Taking ev vs petrol calculator by mileage as the case in point: It depends on the battery size and how empty it is. A charge from near-empty to full takes roughly the battery's capacity in kWh, plus a few percent for charging losses. Divide the kWh drawn by the miles driven afterwards and you have the car's real miles per kWh for that period.

Does charging at home really make that much difference?

Taking ev vs petrol calculator by mileage as the case in point: Yes, usually more than any other single factor. Home charging is typically far cheaper per kWh than public rapid charging, so a driver who charges at home overnight will see a much bigger saving than one who relies on rapid chargers. Work out your own mix of home and public charging and price each part separately for an honest figure.

What is excluded from the EV versus petrol comparison?

On this page, ev vs petrol calculator by mileage is the case in point: Purchase price, depreciation, insurance, servicing, tyre wear and tax. This page compares fuel and charging costs only, and says so, because a break-even figure that hides those costs is not a like-for-like comparison. Add them with stated assumptions if you want a total-cost answer.