What a delivered million BTU costs, in your state

The conversion chain, in full

Nothing here is hidden, so you can check it:

• Electricity. 3,412 BTU per kilowatthour. A million BTU is 293 kWh at the wall. Divide by the coefficient of performance for a heat pump; do not divide at all for resistance, whose coefficient is exactly 1.
• Natural gas. 1,036 BTU per cubic foot, so an Mcf carries 1,036,000 BTU, which is 10.36 therms. Divide by the heater's thermal efficiency.
• Propane. 91,452 BTU per gallon, then divide by thermal efficiency.

Conversion factors: U.S. Energy Information Administration, Energy conversion calculators, Electricity conversion calculator, as printed: 1 kilowatthour=3,412 Btu (standard conversion factor). Captured 2026-10-05; original retrieval recorded 2026-08-06, raw capture not retained. U.S. Energy Information Administration, Energy conversion calculators, Natural gas conversion calculator, as printed: 1 cubic foot=1,036 Btu (based on U.S. average for natural gas delivered to consumers in 2026; estimate), 2026 U.S. average, an EIA estimate. Captured 2026-10-05; original retrieval recorded 2026-08-06, raw capture not retained. U.S. Energy Information Administration, British thermal units (Btu), Sample Btu conversion factors table, Propane row, table cell: 1 gallon=91,452 Btu. Captured 2026-10-05; original retrieval recorded 2026-08-06, raw capture not retained.

Every modelled state, ranked by heat-pump running cost

The table lists the 26 states that have a modelled location on this site and both a published electricity and a published natural gas price. EIA's 2025 annual residential gas series covers 51 jurisdictions (the 50 states and the District of Columbia) and has a figure for 45 of them; it prints NA (not available) for 6: CT, MD, ME, NC, RI, SC. Locations in CT, MD, NC, SC are modelled on this site but not listed here; their calculators use the U.S. average of $15.34 per thousand cubic feet unless you enter your own gas price.

Gas is cheaper to run in 1 of 26 states listed: IL. Everywhere else the heat pump wins on running cost. Either way, this compares running cost only.

Where these prices come from, and what is wrong with them

Electricity. Historical figures from an archived release: U.S. Energy Information Administration, Electric Power Monthly, July 2026 issue (archived), Table 5.6.A — Average Price of Electricity to Ultimate Customers by End-Use Sector, by State, Residential column, May 2026 data (marked preliminary by the publisher). Archived issue retrieved 2026-10-05; these values were first retrieved 2026-08-06 (raw copy of that retrieval kept). EIA's live Table 5.6.A has since moved on to later months and no longer shows these May 2026 values; it is the place to look for a more recent state average.

A state average across every residential customer and every rate plan, for one past month. A pool on a tiered or time-of-use rate is very often paying a marginal rate well above it, because pool heating is added on top of an existing bill.

Natural gas. U.S. Energy Information Administration, Natural Gas Prices — Average Residential Price (Price of Natural Gas Delivered to Residential Consumers), by state, 2025 annual, EIA release of September 30, 2026. Retrieved 2026-10-05. EIA replaces that table with each new release, so after the next one the linked page will show different figures; the September 30, 2026 release used here is kept as a stored copy in this project's evidence archive.

An annual average that folds in the fixed monthly customer charge. Summer pool heating is close to pure commodity gas, so the true marginal price of a summer therm is usually lower than this figure.

Propane. U.S. Energy Information Administration, Weekly U.S. Propane Residential Price, week ending 2026-03-30, EIA release of April 1, 2026. Retrieved 2026-08-06; checked against a stored capture 2026-10-05.

A national figure, and the residential propane series is only collected October through March. Delivered propane prices vary by more between two neighbouring suppliers than this number varies across a year.

Use your marginal rate, not the average

The single most common error in pool energy arithmetic is using an average rate for an incremental load. Pool heating is added on top of everything else your house already uses, so the electricity it consumes is billed at whatever tier or time-of-use period it lands in — which on a tiered residential rate is usually the top one.

Find the rate that applies to the last kilowatthour on your bill, not the total divided by the usage. In some states those two numbers differ by half again, and every cost figure on this site scales linearly with the one you use.

There is a seasonal error stacked on top of the tier error, and it runs the same direction:

The same applies to gas. The annual state average folds in a fixed monthly customer charge you are already paying whether or not you heat the pool. Summer pool heating is close to pure commodity gas, so your marginal therm is usually cheaper than the published average.