EV Charging Calculator kWh: A Step-by-Step Worked Example
The question behind ev charging calculator kwh 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 $3.85 per US gallon, 30 US MPG, electricity at 22 cents per kWh and 4.0 miles per kWh — the petrol car costs about $0.13 per mile and the EV about $0.06 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 calculator kwh: Assumptions used on this page
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. That is the point this page works through for ev charging calculator kwh.
| Input | Value used | Status |
|---|---|---|
| Petrol price | $3.85 per US gallon | Example price |
| Petrol efficiency | 30 US MPG | Assumption |
| Electricity price | 22 cents per kWh | Example price |
| EV efficiency | 4.0 miles per kWh | Assumption |
| Annual mileage | 15,000 miles | Example |
ev charging calculator kwh: How the EV versus petrol comparison works
On this page, ev charging calculator kwh is the case in point: 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 calculator kwh
Take a driver covering 15,000 miles a year. The petrol car does 30 MPG and petrol costs $3.85 per gallon as an example price, so its cost per mile is $3.85 ÷ 30 = $0.13, and 15,000 miles cost $1,925.00 a year. The EV does 4.0 miles per kWh and electricity costs 22 cents per kWh as an example price, so its cost per mile is $0.22 ÷ 4.0 = $0.06, and 15,000 miles cost $825.00 a year. The difference on fuel and charging alone is $1,100.00 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 calculator kwh: Cost at different annual mileages
The table uses the worked-example assumptions above — petrol at $3.85 per gallon (example), 30 MPG, electricity at 22 cents per kWh (example), 4.0 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 | $770.00 | $330.00 | $440.00 |
| 8,000 | $1,026.67 | $440.00 | $586.67 |
| 10,000 | $1,283.33 | $550.00 | $733.33 |
| 12,000 | $1,540.00 | $660.00 | $880.00 |
| 15,000 | $1,925.00 | $825.00 | $1,100.00 |
| 20,000 | $2,566.67 | $1,100.00 | $1,466.67 |
Cost per mile and per 100 miles for ev charging calculator kwh
At the example assumptions, the petrol car costs $0.13 per mile ($12.83 per 100 miles) and the EV costs $0.06 per mile ($5.50 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.
Charging costs: home, public and rapid for ev charging calculator kwh
Charging cost depends on where the electricity comes from, and the spread is wide. Home charging at the example rate of 22 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 75 kWh battery from empty at the home rate used here costs 75 × $0.22 = $16.50; the same charge at double the rate costs $33.00. 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.
ev charging calculator kwh: What the comparison leaves out — and why it matters
Taking ev charging calculator kwh as the case in point: Treat the saving on this page as a fuel-and-charging figure, not a total-cost verdict. It leaves out the price difference between the cars, depreciation, insurance, servicing, tyres and tax, and it assumes one electricity price when real charging is a blend of cheap home charging and expensive public rapid charging. A driver who charges at home will do better than these figures; a driver who lives on rapid chargers may do worse. Add the excluded items with stated assumptions if you want the full comparison.
Common mistakes for ev charging calculator kwh
- On this page, ev charging calculator kwh 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.
- On this page, ev charging calculator kwh is the case in point: 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 charging calculator kwh as the case in point: 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.
- On this page, ev charging calculator kwh is the case in point: Mixing US and imperial gallons is the biggest, because it shifts the answer by about 20 percent with no warning. A UK imperial gallon is about 4.55 litres; a US gallon is about 3.79 litres, so the same car has a higher MPG figure in imperial gallons than in US gallons.
Related calculations for ev charging calculator kwh
On this page, ev charging calculator kwh is the case in point: These pages continue from here: the same method on a neighbouring question, or the calculator that runs the arithmetic for you.
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ev charging calculator kwh: Putting your figure to work
The method earns its keep when you run it on your own numbers. Measure your real cost per mile for each car — your prices, your efficiency, your charging mix — and you can price a journey before you leave and compare two cars on equal terms instead of brochure claims. Keep a small log of date, miles, energy and price, and look at it monthly: a winter efficiency dip, a change in your charging mix and a slow cost creep all show up fast, and each one is something you can act on. That is the point this page works through for ev charging calculator kwh.
Frequently asked questions
Can I use the same method for a diesel car?
Taking ev charging calculator kwh as the case in point: Yes. A diesel car uses the same petrol-side formula — fuel price per gallon divided by MPG — with diesel prices and diesel MPG. The EV side is unchanged. Compare the two cost-per-mile figures the same way, and remember the same exclusions apply.
Does charging at home really make that much difference?
Taking ev charging calculator kwh 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.
How do I work out my own EV versus petrol saving?
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. That is the point this page works through for ev charging calculator kwh.
Should I use US or imperial gallons?
Taking ev charging calculator kwh as the case in point: Use the gallon your country uses, and say which one. A UK imperial gallon is about 4.55 litres and a US gallon is about 3.79 litres, so the same car shows a higher MPG number in imperial gallons. Mixing the two shifts the answer by about 20 percent with no warning.
What is excluded from the EV versus petrol comparison?
On this page, ev charging calculator kwh 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.