What this models
Annual gasoline cost is computed as annual miles ÷ EPA combined MPG × $/gallon. Annual EV charging cost is annual miles ÷ 100 × kWh/100 mi × $/kWh. The EV column also adds the chosen initial price premium in year zero, so an EV needs the running-cost gap to add up to that premium before it pulls ahead.
What this does not model
- Depreciation. Resale value can outweigh fuel savings either direction; track it via the catalog.
- Maintenance. EVs typically save on brake wear, fluids and engine service.
- DCFC vs home charging mix. All charging is assumed at the entered $/kWh.
- Inflation. Prices are held constant in today's dollars.
- Battery degradation. Long-horizon EV efficiency is assumed flat at the entered rate.
Default values
The starting numbers reflect a US-average commuter case: 12,000 mi/yr, 32 MPG combined for the gas car, 28 kWh/100 mi for the EV, $3.20/gallon and $0.16/kWh — within the recent EIA range for retail residential electricity. Adjust to your own data.