How this calculator works
Gas cost is miles ÷ MPG × price per gallon. EV cost is miles ÷ miles-per-kWh, plus charging losses, × your electricity rate. Dividing the EV’s extra price by the yearly savings gives a simple payback period.
Gas cost = Miles ÷ MPG × Gas price
EV cost = Miles ÷ (mi/kWh) × (1 + Loss%/100) × Rate
Payback = Extra EV price ÷ (Gas cost − EV cost)
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Miles driven per year | 12,000 mi |
| Gas car fuel economy | 30 mpg |
| Gas price | 3.25 $/gal |
| EV efficiency | 3.5 mi/kWh |
| Electricity rate | 0.182 $/kWh |
| Charging losses | 10 % |
| Extra purchase price of the EV | $5,000 |
| Result | Value |
|---|---|
| Yearly fuel savings | $614 |
| Payback time | 8.1 years |
| Gas car fuel per year | $1300 |
| EV charging per year | $686 |
| Gas cost per mile | $0.108 |
| EV cost per mile | $0.057 |
Step by step:
- Gas = 12,000 ÷ 30 × $3.25 = $1,300
- EV = 12,000 ÷ 3.5 × 1.1 × $0.182 = $686.4
- Savings = $613.6 per year; payback = $5,000 ÷ $613.6 = 8.1 years
Yearly fuel savings by miles driven
30 mpg at $3.25 vs. 3.5 mi/kWh at 18.2¢.
| Miles per year | Yearly fuel savings | Payback time |
|---|---|---|
| 8,000 | $409 | 12.2 years |
| 12,000 | $614 | 8.1 years |
| 15,000 | $767 | 6.5 years |
| 20,000 | $1023 | 4.9 years |
Common mistakes to avoid
- Comparing to fast-charging prices when you will mostly charge at home (or the reverse).
Frequently asked questions
How much does it cost to charge an EV per mile?
At 3.5 mi/kWh, 10% charging loss and 18.2¢/kWh, about 5.7¢ per mile at home.
Does public fast charging change the math?
Yes — DC fast charging often costs much more per kWh than home charging. Use a blended rate if you fast-charge often.