How much does it cost to heat a pool per month?

A gas pool heater typically runs $200–$500 a month in natural gas or propane, a heat pump runs $50–$150 a month in electricity, and a solar heater costs about $10–$25 a month (mostly your existing pump's power). The gap is driven by fuel type, not heater quality — a heat pump moves heat instead of burning it, so it uses far less energy per degree of warmth.

Why is my gas pool heater so expensive to run?

Gas heaters burn fuel to generate heat directly, so every BTU costs you full price. A 400,000 BTU gas heater running several hours a day can burn through $15–$25 in propane or natural gas per session. Heat pumps avoid this by moving existing heat from the air instead of creating it, which is why they cost 60–80% less to run for the same temperature gain.

Does a pool cover really lower heating costs?

Yes — evaporation is the single biggest source of heat loss on any pool, day or night. According to the U.S. Department of Energy's Energy Saver program, a pool cover can cut heating costs by up to 50–70% by stopping that evaporation, which often pays for the cover itself within one season regardless of which heater type you run.

Pool Heating Cost 2026: What Gas, Heat Pump & Solar Really Cost to Run

Quick answer

Expect to pay $200–$500 a month for a gas pool heater, $50–$150 a month for a heat pump, and $10–$25 a month for solar, based on current U.S. residential electricity rates (18.83¢/kWh average as of July 2026, per the EIA) and typical propane/natural-gas pricing. The gap comes down to physics: a heat pump moves heat instead of burning fuel to create it, so it uses roughly a quarter of the energy per degree of warmth that a gas heater does. Whichever heater you run, a solar cover is the highest-ROI add-on — the DOE’s Energy Saver program credits covers with cutting heating costs up to 50–70% by stopping overnight evaporation.

Monthly running cost by heater type

Heater type	Typical monthly cost	What drives the cost	Best for
Gas (natural gas / propane)	$200–$500	Fuel burned per hour, ~84% efficiency	Fast heat, any weather, occasional use
Heat pump	$50–$150	Electricity rate × BTU output ÷ COP	All-season use above ~50°F
Solar	$10–$25	Just your existing pump's electricity	Sunny climates, patient heating

These are national averages; your actual bill depends on pool size, target temperature, climate, and local energy prices, which range from 12.35¢/kWh in North Dakota to over 40¢/kWh in Hawaii, per EIA state data.

Gas heaters: the fastest, most expensive heat

A gas heater burns natural gas or propane to heat water directly, which is why it can raise a cold pool’s temperature in hours rather than days — and why it’s the priciest heater to run. A 400,000 BTU unit like the Pentair MasterTemp 400 running several hours a session can burn $15–$25 in fuel each time, adding up to that $200–$500 monthly range for regular use. Propane runs roughly 2–3x the cost of natural gas per BTU, so a natural-gas line is worth trenching for if you’ll heat often. Gas makes the most sense for spas, short swim windows, or anyone who heats occasionally rather than running a heater all season.

Heat pumps: the cheapest heat that still needs power

A heat pump doesn’t create heat — it extracts it from the surrounding air and moves it into your pool water, the same principle as a refrigerator running in reverse. That’s measured by COP (coefficient of performance): a heat pump rated COP 5 returns about $5 of heat for every $1 of electricity. At the EIA’s July 2026 average residential rate of 18.83¢/kWh, a mid-size heat pump like the Hayward HeatPro running 8 hours a day typically lands in the $50–$150/month range — often 60–80% less than an equivalent gas heater. The catch: heat pumps lose efficiency as air temperature drops and mostly stop working well below ~50°F, so they’re an all-season tool in warm-to-temperate climates rather than a cold-snap fix.

Solar: nearly free, weather-dependent

Once installed, a solar heater like the SmartPool S601P SunHeater has no fuel cost and adds almost nothing to your electric bill beyond running the pump you already own — that’s the $10–$25/month figure, and it’s really just your pump’s existing draw. The tradeoff is that solar only works when the sun does; sized at 50–100% of your pool’s surface area in a sunny climate, it typically adds 6–12°F and stretches your season by weeks on both ends, but it won’t deliver bathwater on a cloudy week in April.

The single biggest lever: a pool cover

Solar pool cover (bubble or foam)

Highest ROI accessory · Works with any heater type

Cuts evaporation, which the DOE's Energy Saver program identifies as the largest source of pool heat loss.
Reduces heating costs by up to 50–70% according to the same DOE guidance, regardless of whether you run gas, heat pump, or solar.
Often pays for itself within a single swim season on fuel or electricity savings alone.

Check price on Amazon →

Whichever heater you’re running or about to buy, get the cover on order the same day — try Amazon Prime free for 30 days so it ships in two days and starts cutting your bill on the very first heated swim.

Beyond a cover, three more habits move the needle: lower your target temperature by 2°F (each degree adds meaningfully to running cost), run the heater during off-peak electricity hours if your utility offers time-of-use pricing, and keep your pump/filter clean so a heat pump isn’t fighting restricted flow.

Which type actually costs less over a season?

For a typical 20,000-gallon in-ground pool run daily through a 4-month swim season, gas usually totals $800–$2,000 in fuel, a heat pump $200–$600 in electricity, and solar under $100 beyond pump power. Heat pumps close most of that gap in higher upfront price within one to two seasons of savings versus gas — see our best pool heat pump picks for COP-ranked options, or start with the full breakdown of heater types on our best pool heater pillar guide. If you’re deciding between two specific gas brands, our Hayward vs. Pentair comparison covers running-cost differences between the two most common gas lines.

The bottom line

Solar is the cheapest heat you can buy, a heat pump is the best all-season value once you’ve got warm-enough air, and gas is the fast, expensive option for occasional or cold-weather heating. Whatever you choose, add a cover — it’s the one upgrade that cuts the bill on every heater type at once.