Methodology & sources
Every number on EVCostIQ comes from one transparent engine. Below is exactly how we compute total cost of ownership, what each assumption is, where every input comes from, and how often it refreshes. We label estimates as estimates and never present a modeled figure as a licensed third-party value.
The one engine
All tools share a single calculation kernel, so every figure (a result card, the chart, a per-model page) is identical and consistent. Total cost of ownership over your chosen horizon is:
TCO = depreciation + charging/fuel + maintenance + insurance + financing interest + registration/fees − incentives, summed year by year, with a break-even point where one vehicle's cumulative cost crosses another's.
Assumptions (each editable, each dated)
- Charging loss — 12% (default, adjustable). AC home charging wastes roughly 10–15% of electricity between the wall and the battery, so you buy more kWh than you drive on. We add it explicitly (
kWh purchased = kWh used ÷ (1 − loss)). Most calculators omit it, understating EV cost. EPA / SAE J1634-aligned. - Depreciation — transparent estimated curves by powertrain. Cumulative share of MSRP retained each year, calibrated to public iSeeCars and Recurrent studies (EVs historically depreciate faster than gas, though the gap is narrowing). This is a clearly-labeled estimate, not a licensed KBB/Black Book valuation. iSeeCars + Recurrent (calibrated).
- Electricity — EIA residential rates by state (Electric Power Monthly, period ), with a manual override. EIA Electric Power Monthly v2 API.
- Gas — AAA state averages (override available). AAA.
- Maintenance — per-mile by powertrain (EVs lower: no oil, fewer parts). AAA Your Driving Costs (calibrated).
- Insurance — average annual premium by powertrain (EVs ~30% higher). Industry averages (calibrated).
- Financing — standard loan amortization from your APR, term, and down payment.
- Vehicle specs — EPA fueleconomy.gov (efficiency, MPG, range) plus manufacturer MSRP/battery. EPA.
- Plug-in hybrids — a real-world electric/petrol split, not the brochure figure. Official blended figures (often 0.5–2 L/100 km) assume a freshly-charged battery on every trip; real owners do worse. We split each PHEV's distance by a utility factor calibrated to real-world fleet studies —
UF = min(0.85, EV range ÷ (EV range + 55 km))— and cost the electric share at the local electricity rate (charging loss included) plus the remaining share at the car's charge-sustaining (battery-depleted) petrol consumption. That typically prices a PHEV's energy well above the brochure blend and below a pure petrol car — the honest middle. ICCT / Fraunhofer ISI real-world PHEV studies (calibrated); WLTP/EPA specs per model.
Incentives — dated, never baked into the headline
- The federal $7,500 new (30D) and $4,000 used (25E) clean-vehicle credits expired Sept 30, 2025 under the One Big Beautiful Bill Act. We show them as expired and never apply them to a headline cost. IRS.
- The 30C home-charger credit (30% up to $1,000) and the new-vehicle auto-loan interest deduction (up to $10k/yr, 2025–2028, income-limited) are shown as optional, dated items. IRS.
- State and utility incentives are layered per location with a source and an "as of" date.
Freshness & independence
Every page carries a "last refreshed" date tied to the underlying data, not the build time. We take no manufacturer commissions, no utility-territory deals, and no referral fees that change the math. Any affiliate links are disclosed and never affect a calculation. Estimates are for planning, not financial advice — confirm with the official sources.
The data behind every calculator is free to access as machine-readable JSON — the US fleet and per-state rates, plus one file per market. The per-market JSON files are publicly accessible for personal and research use with attribution; bulk redistribution of the compilation is not permitted — see Terms. Every record is sourced and dated; each file's _license and _attribution block states the terms of reuse. A curated index for AI/answer engines lives at /llms.txt.