Applicable scope: Global; verify your exact vehicle and local requirements.
A useful running-cost comparison answers a specific question: what will it cost this owner to acquire, run and eventually sell this vehicle over a defined period? Sticker price and energy cost alone do not capture a car’s ownership economics. Market-dependent taxes, financing, registration, insurance, parking, depreciation and repair exposure can exceed the difference in fuel spending between two powertrains.
Set consistent assumptions
Use the same ownership years, expected distance, currency and inflation treatment for each vehicle. Record purchase price less realistically estimated resale proceeds as depreciation; keep financing charges separate so cash and loan buyers are not blended. Add registration, insurance, energy, inspection, scheduled service, tires, parking and a clearly labelled reserve for unpredictable repairs. The DOE AFDC vehicle calculator illustrates why travel patterns and cost assumptions belong in the input data.
Show the equations, not false precision
Total cost is acquisition costs minus net resale proceeds plus all ongoing costs during the ownership period. Average cost per kilometre divides this total by planned distance. For cash-flow planning, list the timing of large expenditures rather than just averaging a set of costs over five years. Keep currencies local and state the date of prices. Never publish a made-up insurance quote, predicted battery replacement or specific repair bill as a verified average.
Test scenarios that could reverse the result
Run at least low/typical/high mileage, cheaper/more expensive energy and strong/weak resale scenarios. An EV may look economical on home electricity but less attractive with frequent costly public charging; a lower-priced older car may lose its advantage after age-related repair spending. Use official regional consumption figures only within their proper test framework and state that test values are comparative estimates, not promised real-world usage. The best recommendation is the one that remains intelligible when assumptions change.
A practical ownership decision
For transparency, publish a compact assumptions table beside any comparison: annual distance, years owned, electricity and fuel prices, charging mix, estimated resale value and how uncertain maintenance costs were treated. A reader should be able to replace those values without accepting hidden author preferences. Keep ‘budgeted repair reserve’ visibly different from a claim about actual historical repairs.
Safety and verification
This is ownership information, not a vehicle-specific diagnosis, repair authorization or parts compatibility determination. Confirm the exact model, market, service publication and current local rules. For brakes, steering, structural damage, airbags, high-voltage equipment or other safety-critical concerns, use qualified professionals and follow manufacturer emergency instructions.