Where Our Data Comes From
Updated July 21, 2026
Every number on this site derives from official U.S. Energy Information Administration (EIA) data. This page names the exact series, the formula, the units, the publication lag, and the refresh schedule for each. Nothing is projected, modeled, or borrowed from third-party estimates.
Electricity rates and bills
| Number | Formula | Source series | Lag |
|---|---|---|---|
| Average rate (¢/kWh) | residential revenue ÷ residential sales | EIA API v2, electricity/retail-sales, monthly, residential sector (the series behind Electric Power Monthly Table 5.6.a) | ~2 months |
| Average bill ($/month) | residential revenue ÷ residential customer count | ||
| Average usage (kWh/month) | residential sales ÷ residential customer count |
Utility-level rates and the ZIP lookup
| Number | Formula / source | Lag / vintage |
|---|---|---|
| Utility average rate and bill | Same formulas as above, per utility and state, from EIA Form 861-M (monthly sales to ultimate customers, residential). Months failing sanity screens (implied rate under 2¢ or over 75¢/kWh, bill under $10 or over $1,200, sales without customers) are excluded from display. | ~2 months |
| ZIP → utility mapping | NREL/OpenEI, "U.S. Electric Utility Companies and Rates: Look-up by Zip Code (2024)", CC BY 4.0. We use only the ZIP-utility assignment, never its rate columns. | 2024 vintage, updated when NREL publishes |
EIA's monthly survey covers utilities above a size cutoff (roughly 700 utility-state records per month); smaller utilities report only in the annual EIA-861 census and appear in the ZIP lookup by name without monthly numbers.
Gasoline prices by state
| Number | Source | Cadence |
|---|---|---|
| State pump prices (regular, diesel) | AAA state averages. No government source publishes daily pump prices for all 50 states (EIA's weekly survey covers ~10); AAA is the industry-standard series that EIA itself cites. | Weekly refresh of AAA's daily figure |
| State fuel taxes and fees | Tax Foundation total state gasoline taxes/fees, plus the 18.4¢ federal excise | Annual |
| Crude-oil component | EIA WTI Cushing spot, monthly average ÷ 42 gal/bbl | Monthly |
| Refining, distribution & margins | Computed residual: pump price − crude − taxes. Includes fuel-specification and carbon-program costs embedded in prices rather than levied as taxes. | — |
Home heating costs
| Number | Source / formula | Cadence |
|---|---|---|
| Delivered heat cost ($/MMBtu) | fuel price ÷ (heat content per unit × equipment efficiency), so every fuel is on one scale. Heat-content factors from EIA (gas 1.037 MMBtu/Mcf, oil 0.1385/gal, propane 0.0915/gal, electricity 0.003412/kWh); efficiencies from DOE (gas furnace 92%, oil 86%, resistance 100%, heat pump COP 2.8). | — |
| Natural gas price by state | EIA residential price ($/Mcf; 1 Mcf ≈ 10.37 therms) | Monthly |
| Heating oil & propane by state | EIA weekly residential survey (~21 states for oil, ~38 for propane), published October–March | Weekly, in season |
| Electricity by state | our EIA residential rate series (see above) | Monthly |
Prices shown are the most recent complete heating-season (October–March) average for each fuel, so summer and winter builds report the same season until a new one finishes. The calculator's heating load and heat-pump COP are user-adjustable; we do not model home climate, insulation, or time-of-use rates.
EV vs. gas comparison
| Number | Source / formula | Cadence |
|---|---|---|
| EV cost per mile | state residential electricity rate ($/kWh, EIA) ÷ EV efficiency. Default 3.3 mi/kWh (~30 kWh/100 mi, fueleconomy.gov). | Electricity monthly |
| Gas cost per mile | state pump price ($/gal, AAA) ÷ fuel economy. Default 27 MPG (MY2024 new-vehicle real-world average 27.2 MPG, EPA). | Gasoline weekly |
| Annual saving | per-mile gap × miles driven. Default 13,500 mi/yr (FHWA average per driver). | — |
All three defaults are user-adjustable on the page. The comparison is fuel cost only (no purchase price, depreciation, insurance, or maintenance), and home charging is priced at the average residential rate rather than a time-of-use EV tariff.
World prices
| Number | Source | Cadence |
|---|---|---|
| European household electricity / gas prices | Eurostat nrg_pc_204 (electricity, band DC: 2,500–4,999 kWh/yr) and nrg_pc_202 (gas, band D2: 20–199 GJ/yr), all taxes and levies included, CC BY 4.0 | Half-yearly |
| European pump prices (gasoline, diesel) | European Commission Weekly Oil Bulletin, prices with taxes as reported by member states | Weekly (Mon) |
| U.S. comparators on world pages | EIA: our state electricity series averaged over the same semester; residential natural gas (consumption-weighted, 1 Mcf ≈ 303.9 kWh); weekly retail gasoline (regular) and on-highway diesel | Matches the European series |
| Currency conversion | ECB reference rate (USD/EUR): semester average for electricity/gas, same-week rate for fuels | Daily |
Comparability caveats are stated on each world page (consumption bands differ from U.S. usage; Euro-super 95 vs U.S. regular octane conventions; national averages throughout).
What these numbers are, and are not
- They are average effective prices. Revenue divided by sales includes every charge on the bill: energy, delivery, fixed charges, riders, taxes collected through rates. Research on consumer behavior (Ito 2014, American Economic Review) finds households respond to average price, which is why we lead with it.
- They are not tariff prices. Your marginal rate, your utility's fixed charge, and time-of-use differentials will differ from the state average.
- They are official reported data with some estimation. EIA's monthly figures come from Form EIA-861M, a survey of a sample of utilities with imputation for the rest; final census values arrive with the annual EIA-861. EIA revises recent months as final data lands. We re-fetch monthly and log every revision on the data updates page.
Publication lag, disclosed
EIA publishes monthly retail data roughly two months after the fact, typically in the Electric Power Monthly around the 25th. Every page on this site states the actual data month ("Data through April 2026"). We do not project or nowcast unpublished months; a disclosed lag beats undisclosed modeling.
Refresh schedule
The pipeline re-fetches the full EIA series and rebuilds this site monthly, after the Electric Power Monthly release. The "Updated" date on each page is a real data refresh, never a re-dating.
Revisions policy
When EIA revises a previously published value, we adopt the revision and record it (date observed, series, month, old value, new value) in a public log. History is never silently restated: see data updates.
Related resources
EIA's own Electricity Data Browser is the canonical source for this data. The Heatmap-MIT Electricity Price Hub is a complementary project that builds tariff-based estimates with component breakdowns; we link it as a resource, and none of our numbers derive from it.