EV Charger ROI Calculator
Compare home EV charging running cost with petrol and work out the charger payback period.
What does the undefined do?
It compares the yearly cost of charging an EV at home with petrol, and shows how quickly the home charger pays for itself.
- Inputs: charger and installation cost, annual miles, petrol price, petrol economy, EV efficiency and the electricity rate.
- Output: the payback period in years plus the annual petrol and electric cost comparison.
- Method: annual petrol cost versus annual electric cost, with payback from the installed cost divided by annual savings.
Quick answer
A charger costing 2,000 installed, saving about 986 a year against petrol, pays for itself in roughly two years, after which the saving is pure gain.
What This Calculator Really Does
A home charger is a small capital cost that produces a stream of savings every mile you drive. The comparison is simple: petrol costs miles divided by miles per gallon, times the price per gallon, while home charging costs miles divided by miles per kWh, times the price per kWh. Because electric motors are far more efficient, the per-mile cost is usually much lower, so the savings accumulate quickly. This tool divides the installed cost by the annual saving to give the payback period. The result is sensitive to the petrol price, the electricity rate and whether you can charge on a cheap overnight tariff, where off-peak rates can shorten payback substantially. Public fast charging is far more expensive than home charging and can erase much of the advantage.
The formula it uses
Annual petrol = miles / mpg x gas price. Annual electric = miles / miles per kWh x rate. Savings = petrol minus electric. Payback = installed cost / savings.
Worked example with real numbers
Charger and installation of 2,000, 12,000 miles a year, petrol at 3.5 a gallon and 28 mpg give about 1,500 a year in petrol. Using 3.5 miles per kWh at 0.15 a unit gives about 514 in electricity, so the saving is about 986 and payback is roughly two years.
Common mistakes to avoid
- Ignoring the cost of a home electrical upgrade, which some homes need before a charger can be fitted.
- Comparing home charging with petrol while actually relying on expensive public fast charging.
- Assuming the same efficiency in winter, when cold weather cuts EV range and raises cost per mile.
Assumptions and limitations
Efficiency and prices are held constant, and no off-peak tariff, solar or battery is modelled. Charger incentives, electrical upgrades and public charging are excluded.
Disclaimer
This is an educational estimate, not a quote or financial advice. Real running costs depend on your tariff, driving, weather and the vehicle, so verify with current prices before buying.
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Frequently Asked Questions
How is the undefined calculated?
Petrol cost per year is miles divided by mpg times the petrol price, electric cost is miles divided by miles per kWh times the rate, and payback is installed cost divided by the annual saving. The steps panel shows each part.
What do I need to use the undefined?
Charger and installation cost, annual miles, petrol price and economy, EV efficiency in miles per kWh, and your electricity rate.
What does the result from the undefined show?
The charger payback period in years plus a side-by-side of annual petrol and electric running costs.
Is a home charger worth it if I drive few miles?
Less so. Payback lengthens as annual miles fall, so low-mileage drivers may be better off with a standard plug and occasional public charging.
Do off-peak tariffs really help?
Often yes. Charging overnight on a cheap rate can cut the per-mile cost further and shorten payback, provided you can schedule charging to those hours.
Is the undefined really free?
Yes — 100 percent free, no sign-up, and everything runs in your browser.
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