How we calculate
Every calculator here is built on published formulas and transparent assumptions. Each tool has a “How we calculate” panel that spells out its exact math; this page covers the shared defaults and the sources behind them. When you enter your own numbers, these defaults don’t matter — but they’re honest starting points.
National-average defaults
| Figure | Default | Source · verified |
|---|---|---|
| Average annual cost to own (new) | $12,863 | AAA — Your Driving Costs 2026 · 2026-09-15 |
| Default annual mileage | 13,500 | U.S. DOT Federal Highway Administration · 2026-11-07 |
| Default gas price | 4.15 | AAA — Your Driving Costs 2026 (study-time national average, $4.152) · 2026-09-15 |
| Default electricity rate | 0.18 | AAA — Your Driving Costs 2026 (home charging, 18.0¢/kWh) · 2026-09-15 |
| Default full-coverage insurance | $2,098 | AAA — Your Driving Costs 2026 (national average) · 2026-09-15 |
| Default gas fuel economy | 28 | EPA fuel economy (typical mainstream new gas vehicle) · 2026-11-07 |
| Default EV efficiency | 3.3 | EPA fuel economy (typical new EV, combined) · 2026-11-07 |
| First-year depreciation | 20% | Industry depreciation studies (new-vehicle average) · 2026-11-07 |
| Five-year depreciation | 45% | Industry depreciation studies (new-vehicle average) · 2026-11-07 |
The federal EV tax credit
The federal clean-vehicle tax credit (up to $7,500 for a new EV and $4,000 for a used one) ended for vehicles acquired after 2025-09-30. Our EV vs. gas calculator defaults it to $0 and only lets you add state or utility incentives, which vary by location.
State-specific figures
Registration fees, sales tax, dealer doc fees and average insurance differ by state. Each state page carries its own figures with a dated primary source, and a state is only published once every figure is verified — we never fill a state in from memory.
All results are estimates for planning only and are not financial advice. Rates, taxes and fees change; confirm exact figures with a lender, insurer or your state DMV before you decide.