Electric Car vs Petrol Cost Calculator: Running Costs Compared

Electric Car vs Petrol Cost Calculator is one of those questions that sounds simple until you try to answer it for your own car. The number depends on the car, the journey, the weather and how you drive, so there is no single figure that fits every driver. What this page does instead is give you the method, so you can work out your own figure and know exactly what it means.

Below you will find the formula, a worked example with every step shown, a conversion table, and the factors that push the result up or down. That is the point to carry into electric car vs petrol cost calculator: the answer follows from the assumptions, so write yours down before you trust the result. Fuel prices and efficiency figures used in examples are labelled as examples, because they change constantly and differ by place and by car.

How the EV versus petrol cost comparison works — electric car vs petrol cost calculator

The comparison is a cost-per-mile calculation done twice, once for each car, using the same annual mileage. For the petrol car, cost per mile = fuel price per gallon ÷ MPG. For the electric car, cost per mile = electricity price per kWh ÷ miles per kWh. Multiply each by your annual miles and you have the annual fuel or charging cost. The assumptions used as the worked example on this page are: petrol at $4.05 per gallon as an example price, a petrol car at 38 MPG, electricity at $0.25 per kWh as an example price, and an EV doing 3.5 miles per kWh. None of those are current prices or official figures — they are stated assumptions so you can see the working and substitute your own. What the comparison deliberately leaves out matters too: insurance, depreciation, servicing, tyre wear and purchase price are excluded from the fuel-cost comparison, and a break-even claim that hides them is not a like-for-like comparison.

Worked example: the same miles, two fuel bills — electric car vs petrol cost calculator

Take a driver covering 12,000 miles a year. The petrol car in this example does 38 MPG and petrol costs $4.05 per gallon as an example price, so its cost per mile is $4.05 ÷ 38 = $0.11 per mile, and 12,000 miles cost 12,000 × $0.11 = $1,278.95 a year. The EV does 3.5 miles per kWh and electricity costs $0.25 per kWh as an example price, so its cost per mile is $0.25 ÷ 3.5 = $0.07 per mile, and 12,000 miles cost $857.14 a year. The difference on fuel and charging alone is $421.80 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 — electric car vs petrol cost calculator

The table uses the worked-example assumptions above — petrol at $4.05 per gallon (example), 38 MPG, electricity at $0.25 per kWh (example), 3.5 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 $639.47 $428.57 $210.90
10,000 $1,065.79 $714.29 $351.50
12,000 $1,278.95 $857.14 $421.80
15,000 $1,598.68 $1,071.43 $527.26
20,000 $2,131.58 $1,428.57 $703.01

What the comparison leaves out — and why it matters — electric car vs petrol cost calculator

A fuel-cost saving is not a total-cost saving, and the two get confused constantly. That is the point to carry into electric car vs petrol cost calculator: the answer follows from the assumptions, so write yours down before you trust the result. Purchase price, depreciation, insurance, servicing, tyre wear and tax sit outside the fuel maths on this page, and they can outweigh several years of fuel savings in either direction. An EV typically has fewer moving parts to service but can cost more to insure and can depreciate differently; a petrol car is usually cheaper to buy but costs more to fuel. Break-even calculations that only count fuel are really answering a narrower question — how long until the fuel saving covers a stated price gap — and they should say so. If you want a true break-even, list every cost on both sides, state each assumption, and check how sensitive the answer is to the electricity price, because that single input moves the EV side more than any other.

Common mistakes — electric car vs petrol cost calculator

The most common mistake is mixing gallons: US and imperial gallons differ by about 20 percent, so a figure converted with the wrong gallon is wrong by the same margin. That is the point to carry into electric car vs petrol cost calculator: the answer follows from the assumptions, so write yours down before you trust the result. Next is trusting a single tank — one short fill or one unusual journey can tilt it badly — instead of averaging several. Third is reading the trip meter without resetting it at the fill, which mixes miles from before the fill into the calculation. Fourth is using the tank's capacity instead of the gallons actually pumped; the capacity is not the amount you used. And fifth is comparing a dashboard figure with a brim-to-brim figure as if they were the same measurement: the dashboard estimates from the engine's data, the brim-to-brim method measures what actually went in, and they disagree by a few percent in either direction.

Related calculations — electric car vs petrol cost calculator

If this page answered your question, these pages take the next step — the same method applied to a closely related question, or the calculator that does the arithmetic for you. Read the figures on this page about electric car vs petrol cost calculator as a worked illustration, not as prices or efficiencies you should quote elsewhere.

Putting your electric car vs petrol cost calculator figure to work

Putting the figure to work is where the method pays off. That is the point to carry into electric car vs petrol cost calculator: the answer follows from the assumptions, so write yours down before you trust the result. Once you know your own MPG, measured brim-to-brim over several tanks, you can price any journey before you set off: multiply the miles by the fuel price divided by your MPG, and the answer is the fuel cost of that trip at that example price. You can also compare cars honestly, because you are comparing measured figures rather than brochure claims. Keep a simple log — date, miles, gallons, price — and review it monthly. Patterns show up quickly: a winter dip, a motorway improvement, a slow decline that points to tyre pressures or a change in routes. 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

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

Not always. That is the point to carry into electric car vs petrol cost calculator: the answer follows from the assumptions, so write yours down before you trust the result. 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 do I work out my own EV versus petrol saving?

Use the same mileage for both cars. Read the figures on this page about electric car vs petrol cost calculator as a worked illustration, not as prices or efficiencies you should quote elsewhere. For the petrol car, divide the fuel price per gallon by its MPG to get cost per mile. For the EV, divide the electricity price per kWh by its miles per kWh. Multiply each by your annual miles and subtract. Use your own prices — especially your real charging mix of home and public charging — rather than the example prices on this page.

What is excluded from the EV versus petrol comparison?

Purchase price, depreciation, insurance, servicing, tyre wear and tax. For electric car vs petrol cost calculator, the same reasoning applies — substitute your own prices and efficiencies and the steps on this page still hold. 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.

Does charging at home really make that much difference?

Yes, usually more than any other single factor. For electric car vs petrol cost calculator, the same reasoning applies — substitute your own prices and efficiencies and the steps on this page still hold. 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.

How sensitive is the saving to the electricity price?

Very sensitive. For electric car vs petrol cost calculator, the same reasoning applies — substitute your own prices and efficiencies and the steps on this page still hold. Doubling the electricity price doubles the EV's charging cost per mile, while the petrol side is unchanged. That is why this page states its example prices openly: change the electricity price to the one you actually pay and the saving changes with it, sometimes by enough to change the conclusion.