Method and sources
Every formula, every number, where it came from
Gas or Plug is arithmetic you can check with a pencil. Sources were read on October 27, 2026.
The formulas
- Car
gallons = miles ÷ MPGkWh = miles ÷ 100 × kWh per 100 milesThe EPA's kWh per 100 miles is measured at the wall, so it already includes charging losses.- Home heat
heat delivered (Btu) = therms × 100,000 × AFUEheat pump kWh = heat ÷ (HSPF2 × 1,000)electric resistance kWh = heat ÷ 3,412.14HSPF2 is Btu of heat per watt-hour over a rated season in a mild test climate. In colder places a heat pump's real seasonal figure is lower, so type a lower HSPF2 if you live somewhere cold. Not counted separately: the electricity a gas furnace's blower uses, and a heat pump's backup heat on the coldest days.- Hot water
heat a year (Btu) = gallons a day × 8.34 lb × temperature rise × 365therms = heat ÷ (UEF × 100,000)kWh = heat ÷ (UEF × 3,412.14)The default day (55 gallons, 58°F water heated to 125°F) is the U.S. DOE test's medium-usage day.- Lawn mower
kWh = watt-hours × charges ÷ 1,000 ÷ charger efficiencyGasoline is the gallons you buy for it.- Money and CO2
cost = units × pricepayback = (electric price − rebates − gas price) ÷ yearly savingbreak-even electricity price = gas-side cost ÷ electric-side kWhCO2: 8.887 kg per gallon of gasoline, 5.3 kg per therm of natural gas, and 0.348 kg per kWh of electricity (U.S. average) unless you enter your own grid figure. Ten-year totals multiply one year by ten: no price changes, no discounting.
What is not counted
Upkeep, repairs, insurance, financing, resale value, installation, a utility's fixed monthly charges, and how fuel and power prices change. Those can matter as much as energy, and they vary too much from home to home for an honest average.
State average prices
Used whenever you leave a price blank. Your own bill is more accurate: divide what you paid (with delivery charges and taxes) by the units used. Natural gas is converted from dollars per thousand cubic feet at 10.37 therms per Mcf (EIA). Gasoline is the state's own figure where EIA publishes one, otherwise its region's. For Alaska, Arizona, Hawaii, Nevada and Oregon that is EIA's West Coast less California figure, because California's higher prices pull the whole West Coast average up.
| State | Electricity ¢/kWh | Natural gas $/therm | Gasoline $/gal | Gasoline figure |
|---|---|---|---|---|
| United States (national average) | 18.16 | 1.479 | 4.269 | U.S. average |
| Alabama | 16.33 | 1.693 | 3.702 | Gulf Coast (PADD 3) |
| Alaska | 29.41 | 1.250 | 4.868 | West Coast less California (PADD 5) |
| Arizona | 15.05 | 1.792 | 4.868 | West Coast less California (PADD 5) |
| Arkansas | 14.37 | 1.856 | 3.702 | Gulf Coast (PADD 3) |
| California | 29.75 | 2.122 | 5.888 | California |
| Colorado | 17.17 | 1.077 | 4.458 | Colorado |
| Connecticut | 24.51 | 1.623 (2024) | 4.199 | New England (PADD 1A) |
| Delaware | 18.70 | 1.540 | 4.251 | Central Atlantic (PADD 1B) |
| District of Columbia | 25.98 | 1.608 | 4.251 | Central Atlantic (PADD 1B) |
| Florida | 14.99 | 2.457 | 4.017 | Florida |
| Georgia | 15.90 | 1.969 | 3.832 | Lower Atlantic (PADD 1C) |
| Hawaii | 47.18 | 5.051 | 4.868 | West Coast less California (PADD 5) |
| Idaho | 13.37 | 0.742 | 4.458 | Rocky Mountain (PADD 4) |
| Illinois | 19.32 | 1.085 | 4.269 | Midwest (PADD 2) |
| Indiana | 17.02 | 1.108 | 4.269 | Midwest (PADD 2) |
| Iowa | 17.06 | 1.023 | 4.269 | Midwest (PADD 2) |
| Kansas | 15.47 | 1.428 | 4.269 | Midwest (PADD 2) |
| Kentucky | 13.80 | 1.372 | 4.269 | Midwest (PADD 2) |
| Louisiana | 12.87 | 1.677 | 3.702 | Gulf Coast (PADD 3) |
| Maine | 32.11 | 1.827 (2024) | 4.199 | New England (PADD 1A) |
| Maryland | 21.40 | 1.556 (2024) | 4.251 | Central Atlantic (PADD 1B) |
| Massachusetts | 30.48 | 2.417 | 4.145 | Massachusetts |
| Michigan | 22.99 | 1.053 | 4.269 | Midwest (PADD 2) |
| Minnesota | 17.20 | 1.059 | 4.146 | Minnesota |
| Mississippi | 14.43 | 1.606 | 3.702 | Gulf Coast (PADD 3) |
| Missouri | 16.02 | 1.441 | 4.269 | Midwest (PADD 2) |
| Montana | 15.57 | 0.867 | 4.458 | Rocky Mountain (PADD 4) |
| Nebraska | 13.54 | 1.099 | 4.269 | Midwest (PADD 2) |
| Nevada | 12.72 | 1.267 | 4.868 | West Coast less California (PADD 5) |
| New Hampshire | 27.64 | 1.795 | 4.199 | New England (PADD 1A) |
| New Jersey | 24.61 | 1.370 | 4.251 | Central Atlantic (PADD 1B) |
| New Mexico | 16.51 | 0.948 | 3.702 | Gulf Coast (PADD 3) |
| New York | 28.65 | 1.695 | 4.249 | New York |
| North Carolina | 14.95 | 1.583 (2024) | 3.832 | Lower Atlantic (PADD 1C) |
| North Dakota | 13.31 | 0.916 | 4.269 | Midwest (PADD 2) |
| Ohio | 19.38 | 1.336 | 4.380 | Ohio |
| Oklahoma | 14.82 | 1.387 | 4.269 | Midwest (PADD 2) |
| Oregon | 15.92 | 1.611 | 4.868 | West Coast less California (PADD 5) |
| Pennsylvania | 21.77 | 1.450 | 4.251 | Central Atlantic (PADD 1B) |
| Rhode Island | 28.18 | 2.089 (2024) | 4.199 | New England (PADD 1A) |
| South Carolina | 15.76 | 1.631 (2024) | 3.832 | Lower Atlantic (PADD 1C) |
| South Dakota | 15.15 | 0.951 | 4.269 | Midwest (PADD 2) |
| Tennessee | 13.42 | 1.142 | 4.269 | Midwest (PADD 2) |
| Texas | 15.91 | 1.873 | 3.632 | Texas |
| Utah | 13.31 | 0.983 | 4.458 | Rocky Mountain (PADD 4) |
| Vermont | 23.84 | 1.736 | 4.199 | New England (PADD 1A) |
| Virginia | 17.64 | 1.619 | 3.832 | Lower Atlantic (PADD 1C) |
| Washington | 14.63 | 1.699 | 5.203 | Washington |
| West Virginia | 16.31 | 1.331 | 3.832 | Lower Atlantic (PADD 1C) |
| Wisconsin | 19.41 | 1.036 | 4.269 | Midwest (PADD 2) |
| Wyoming | 14.43 | 1.132 | 4.458 | Rocky Mountain (PADD 4) |
Sources
- U.S. Energy Information Administration: Electric Power Monthly, Table 5.6.A (August 2026, preliminary)Average residential electricity price for each state.
- U.S. Energy Information Administration: Natural Gas Prices: residential, annualAverage residential natural gas price for each state (2025; 2024 where 2025 is not published).
- U.S. Energy Information Administration: Frequently asked questions: natural gas units1,000 cubic feet of natural gas = 1.037 MMBtu = 10.37 therms.
- U.S. Energy Information Administration: Gasoline and Diesel Fuel Update (week of October 26, 2026)Regular gasoline price: the state where EIA reports one, otherwise its region.
- U.S. Environmental Protection Agency: Greenhouse Gas Equivalencies Calculator: calculations and references8,887 grams of CO2 per gallon of gasoline; 0.0053 metric tons of CO2 per therm of natural gas.
- U.S. Environmental Protection Agency: eGRID summary data (2023 data, Revision 2, June 12, 2025)U.S. total output CO2 rate 767.209 lb/MWh (0.348 kg per kWh), the default grid figure.
- U.S. Code of Federal Regulations: 10 CFR Part 430, Subpart B, Appendix E: water heater test methodMedium-usage day of 55 gallons; supply water 58°F, delivered at 125°F.
- U.S. Department of Energy and EPA: fueleconomy.govWhere to look up MPG and kWh per 100 miles for a car.