Our Methods
DriveCost Calculation Methodology & Formulas
DriveCost operates on complete mathematical transparency. All vehicle cost estimates are generated using published Environmental Protection Agency (EPA) specs, documented engineering formulas, empirical maintenance age-bands, and clearly labeled data confidence tiers. This page documents every formula used in our calculation engine.
1. Gasoline Fuel Expenditure Model
Standard window stickers list a single "Combined MPG" rating based on 55% city and 45% highway driving. DriveCost allows users to customize their city/highway split to compute a realistic weighted MPG:
Weighted Fuel Efficiency (MPG):
Estimated MPG = (City % × City MPG) + (Highway % × Highway MPG)
Annual Fuel Gallons:
Annual Gallons = Annual Miles ÷ Estimated Weighted MPG
Annual Fuel Expenditure ($):
Annual Fuel Cost = Annual Gallons × Gasoline Price per Gallon
2. Electric Vehicle (BEV) Charging Model
EV energy consumption is measured in kilowatt-hours per 100 miles (kWh/100mi). Our engine incorporates charging losses (wall-to-battery efficiency overhead) and blended home/public electricity tariffs:
Raw Energy Consumed (kWh):
Consumed kWh = Annual Miles × (kWh per 100 miles ÷ 100)
Total Purchased Electricity (kWh):
Purchased kWh = Consumed kWh × (1 + [Charging Loss % ÷ 100])
Blended Electricity Rate ($/kWh):
Blended Rate = (Home % × Home Rate) + (Public % × Public Rate)
Annual EV Charging Expenditure ($):
Annual Charging Cost = Purchased kWh × Blended Rate
3. Plug-In Hybrid Electric Vehicle (PHEV) Dual-Powertrain Model
Plug-in hybrids utilize both grid electricity and gasoline. DriveCost models daily driving distance against the vehicle's EPA electric-only range to estimate electric vs gas miles:
Daily Distance = Annual Miles ÷ 365
Electric Fraction = Min(1.0, EPA All-Electric Range ÷ Daily Distance)
Electric Miles = Annual Miles × Electric Fraction
Gasoline Miles = Annual Miles × (1.0 − Electric Fraction)
Total PHEV Cost = Electric Cost(Electric Miles) + Gasoline Cost(Gasoline Miles)
4. Age-Banded Maintenance & Tire Schedule
Maintenance costs scale with vehicle age, powertrain complexity, and accumulated mileage. DriveCost classifies vehicles by powertrain type (Gasoline, Diesel, Hybrid, PHEV, Electric) and evaluates cost across four distinct age bands:
| Powertrain Category | Years 0 – 2 (New) | Years 3 – 5 | Years 6 – 10 | Years 11+ (Older) |
|---|---|---|---|---|
| Gasoline (ICE) | $420 Maint / $130 Tires | $560 Maint / $160 Tires | $780 Maint / $200 Tires | $1,050 Maint / $240 Tires |
| Diesel | $520 Maint / $130 Tires | $680 Maint / $160 Tires | $900 Maint / $200 Tires | $1,200 Maint / $240 Tires |
| Gasoline Hybrid (HEV) | $420 Maint / $130 Tires | $540 Maint / $160 Tires | $720 Maint / $200 Tires | $950 Maint / $240 Tires |
| Electric Vehicle (BEV) | $380 Maint / $150 Tires | $480 Maint / $180 Tires | $640 Maint / $220 Tires | $850 Maint / $260 Tires |
* Note: Figures reflect baseline 15,000 miles per year and scale linearly with user-entered annual mileage.
5. Residual Value Depreciation Model
Depreciation measures the loss in vehicle asset value over time. DriveCost implements a standard logarithmic decay curve based on historical automotive resale data:
Year 1 Value Retained: Year 1 Residual = Purchase Price × (1.0 − 0.20)
Years 2+ Value Retained: Year N Residual = Year 1 Residual × (1.0 − 0.10)^(N − 1)
Total Depreciation Loss ($): Depreciation = Purchase Price − Year N Residual
6. 5-Year Total Cost of Ownership (TCO) & Break-Even
Annual Operating Cost = Annual Energy + Maintenance + Tires + Insurance + Fees
5-Year Total Cost = (Annual Operating Cost × 5) + 5-Year Depreciation
Break-Even (Years) = Upfront Price Difference ÷ Annual Operating Savings
Data Confidence Tier System
- EPA-Rated — Official laboratory testing data from fueleconomy.gov.
- Estimated — Empirical statistical models for maintenance, tires, and residual depreciation.
- National / State Average — Current fuel and electricity rates from the EIA.
- Your Input — Custom numbers entered by the user, evaluated directly.