EV Charging Cost vs Petrol Calculator: A Step-by-Step Worked Example

The question behind ev charging cost vs petrol calculator 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 $3.60 per US gallon, 38 US MPG, electricity at 31 cents per kWh and 4.2 miles per kWh — the petrol car costs about $0.09 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 charging cost vs petrol calculator: Assumptions used on this page

For ev charging cost vs petrol calculator, the point is this: 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 $3.60 per US gallon Example price
Petrol efficiency 38 US MPG Assumption
Electricity price 31 cents per kWh Example price
EV efficiency 4.2 miles per kWh Assumption
Annual mileage 12,000 miles Example

ev charging cost vs petrol calculator: How the EV versus petrol comparison works

For ev charging cost vs petrol calculator, 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.

Worked example: the same distance, two energy bills for ev charging cost vs petrol calculator

Take a driver covering 12,000 miles a year. The petrol car does 38 MPG and petrol costs $3.60 per gallon as an example price, so its cost per mile is $3.60 ÷ 38 = $0.09, and 12,000 miles cost $1,136.84 a year. The EV does 4.2 miles per kWh and electricity costs 31 cents per kWh as an example price, so its cost per mile is $0.31 ÷ 4.2 = $0.07, and 12,000 miles cost $885.71 a year. The difference on fuel and charging alone is $251.13 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.

ev charging cost vs petrol calculator: Cost at different annual mileages

The table uses the worked-example assumptions above — petrol at $3.60 per gallon (example), 38 MPG, electricity at 31 cents per kWh (example), 4.2 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 $568.42 $442.86 $125.56
8,000 $757.89 $590.48 $167.42
10,000 $947.37 $738.10 $209.27
12,000 $1,136.84 $885.71 $251.13
15,000 $1,421.05 $1,107.14 $313.91
20,000 $1,894.74 $1,476.19 $418.55

Cost per mile and per 100 miles for ev charging cost vs petrol calculator

At the example assumptions, the petrol car costs $0.09 per mile ($9.47 per 100 miles) and the EV costs $0.07 per mile ($7.38 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.

ev charging cost vs petrol calculator: Charging costs: home, public and rapid

Charging cost depends on where the electricity comes from, and the spread is wide. Home charging at the example rate of 31 cents per kWh is the cheapest common option; public rapid charging can cost two to three times as much per kWh, and that difference matters more than the car's efficiency. As an example, filling a 50 kWh battery from empty at the home rate used here costs 50 × $0.31 = $15.50; the same charge at double the rate costs $31.00. In practice a battery is rarely charged from empty, and charging losses mean slightly more electricity is drawn from the plug than the battery stores — typically a few percent — so treat the fill-up figure as approximate. Work out your own mix of home and public charging, price each part separately, and only then compare the totals. A driver who charges at home overnight will beat the figures on this page; a driver who relies on rapid chargers may not.

What the comparison leaves out — and why it matters for ev charging cost vs petrol calculator

Taking ev charging cost vs petrol calculator as the case in point: 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.

ev charging cost vs petrol calculator: Common mistakes

  • 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. That is the point this page works through for ev charging cost vs petrol calculator.
  • 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. That is the point this page works through for ev charging cost vs petrol calculator.
  • Treating the example prices on this page as current prices is the last mistake. Fuel and electricity prices move constantly, so always substitute the prices you actually pay before trusting any saving. That is the point this page works through for ev charging cost vs petrol calculator.
  • Taking ev charging cost vs petrol calculator as 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.

ev charging cost vs petrol calculator: Related calculations

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. That is the point this page works through for ev charging cost vs petrol calculator.

Putting your figure to work for ev charging cost vs petrol calculator

For ev charging cost vs petrol calculator, the point is this: Use the result as a tool, not a verdict. Re-run the two divisions with your own prices and efficiencies whenever they change, and the comparison stays honest. A monthly log — miles, energy used, price paid — is enough to spot the patterns that matter: colder months cost more per mile for an EV, a new charging habit shifts the average, and a petrol car driven more in town drifts the other way. Measured figures beat remembered ones, and the method on this page is built for measured figures.

Frequently asked questions

How many kWh does it take to charge an EV?

Taking ev charging cost vs petrol calculator 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 an EV cost more to insure?

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. That is the point this page works through for ev charging cost vs petrol calculator.

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

On this page, ev charging cost vs petrol calculator is the case in point: 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 do I work out my own EV versus petrol saving?

Taking ev charging cost vs petrol calculator as the case in point: Use the same mileage for both cars. 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?

Taking ev charging cost vs petrol calculator as 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.