Pool heater running cost calculator
All five heating options priced side by side, on your rates rather than a national average.
Quick picks
The products behind the rows in the table, including the one the table argues against.
| # | Product | Best for | Price |
|---|---|---|---|
| 1 | No photo Usually the cheapest row Hayward HeatPro Pool Heat Pump About a fifth of electric resistance for the same delivered heat. | Lowest running cost per degree when you want real temperature control | |
| 2 | No photo The $0.00 row SmartPool SunHeater S601P Solar Heating System Nothing to run, on the sun's schedule. | Adding real heat with no running cost, on a sunny site | |
| 3 | No photo Shrinks every row at once Sun2Solar 1200 Series Crystal Clear Solar Cover The calculation scales with your heat loss. Cut the loss and every number falls. | Most pools, most budgets — the default recommendation | |
| — | No photo The row to avoid An electric resistance pool heater Cheap to buy, and the most expensive line in the table on a full-size pool. | Spas and very small above-ground pools only |
#ad We earn a commission if you buy through this link, at no extra cost to you. It never changes the ranking. How this site is funded. Prices last checked September 2, 2026.
What will it cost to heat your pool?
For a monthly figure, use your overnight drop x the nights you heat.
Seeded with US residential averages from the EIA. Replace them with the numbers on your own bill — residential electricity varies roughly threefold across US states, which moves this answer more than anything else on the page.
These are assumptions rather than published figures, which is exactly why they are editable. Your heater’s data plate has the real numbers.
Falls as the air gets colder. 5.0 is a mid-range warm-weather figure.
1,666,000 BTU — $17.91 to $89.55
Depending entirely on what you heat with. That spread is the whole argument.
| Method | Per million BTU | This heat-up |
|---|---|---|
| Solar (cover or panels)No fuel | $0.00 | $0.00 |
| Electric heat pumpCOP 5 | $10.75 | $17.91 |
| Natural gas82% efficient | $28.36 | $47.24 |
| Propane82% efficient | $35.66 | $59.41 |
| Electric resistanceCOP 1.0 | $53.75 | $89.55 |
| 20,000 gal x 8.33 x 10°F = 1,666,000 BTU | energy needed |
| Electricity: $0.1834 ÷ 3,412 x 1,000,000 = $53.75 | per million BTU purchased |
| Natural gas: $24.09 ÷ 1.036 = $23.25 | per million BTU purchased |
| Propane: $2.674 ÷ 91,452 x 1,000,000 = $29.24 | per million BTU purchased |
| Heat pump: $53.75 ÷ 5 = $10.75 | per million BTU delivered |
| Gas: $23.25 ÷ 0.82 = $28.36 | per million BTU delivered |
This is the cost of a one-time temperature rise. Your monthly bill is dominated by replacing heat that escapes — put your overnight temperature drop into the rise field, multiply by the nights you heat, and you have your running cost. Every constant here is listed with its source on our methodology page.
How it works
Two steps, and the second is the one that inverts the ranking.
| Electricity: $/kWh ÷ 3,412 x 1,000,000 | |
| Natural gas: $/Mcf ÷ 1.036 | |
| Propane: $/gal ÷ 91,452 x 1,000,000 |
Energy contents from the EIA's published conversion factors. At this stage electricity looks by far the most expensive, which is exactly the comparison that gets published and exactly why it misleads.
| Heat pump: ÷ coefficient of performance | |
| Gas or propane: ÷ thermal efficiency | |
| Electric resistance: ÷ 1.0 | |
| Solar: no fuel to divide |
The ranking flips completely
A heat pump moves heat rather than making it, delivering several units for every one it draws. That is why electricity is simultaneously the cheapest and the most expensive way to heat a pool, depending entirely on the machine on the end of it.
Put your own numbers in
The calculator is seeded with US residential averages from the EIA, and you should replace them. Residential electricity varies roughly threefold across US states, which moves the answer more than any other input on the page. Your rate is on your bill.
The equipment fields matter too, and they are assumptions rather than published figures — which is exactly why they are editable. A heat pump’s coefficient of performance falls as the air cools, so a shoulder-season figure is lower than the summer one manufacturers advertise. What that does to the cost.
Heat-up cost is not your monthly bill
The calculator prices a one-time temperature rise. Your monthly bill is mostly maintenance — replacing heat that escapes, about 70% of it by evaporation.
To get a running-cost figure, put your overnight temperature drop into the temperature-rise field, then multiply the result by the nights you heat. That is your actual bill, and it is usually the number people are looking for.
And before spending anything on the supply side, work out what a cover would do to the demand side. Every row in the table scales with your heat loss.
Every pick, in detail
What each one publishes, what is good and bad about it, and — the section this category usually omits — what we could not judge without owning one.
Hayward HeatPro Pool Heat Pump
If you are heating a pool with electricity, this is the shape of machine to do it with. A heat pump moves heat instead of making it, and at the assumptions we publish it delivers a million BTU into the water for about a fifth of what an electric resistance heater costs to deliver the same. It is slower than gas and it fades as the air gets colder, which is exactly when you want it — that trade is the whole decision.
Best for Lowest running cost per degree when you want real temperature control
| Type | Air-source heat pumpThe manufacturer publishes no retrievable specification sheet; figure is as listed at retail. | Retail listing |
|---|---|---|
| Rating convention | Rated by BTU/hr OUTPUTThis is the trap in the category. Gas heaters are rated by fuel INPUT, heat pumps by heat OUTPUT. A 140,000 BTU heat pump and a 140,000 BTU gas heater do not deliver the same heat. | Published standard |
| Cost per million BTU delivered | About $10.75 at our published assumptionsUS average residential electricity at 18.34 cents/kWh (EIA, June 2026) and an assumed COP of 5.0. Both are substitutable on our running-cost calculator. | Our arithmetic |
- Cheapest running cost per delivered BTU of any controllable heater
- No gas line, no combustion, no flue
- Holds a set temperature rather than depending on the weather
- Slow — expect most of a day to move a full-size pool ten degrees
- Efficiency falls with air temperature, so it is weakest in the shoulder season
- High purchase price against a gas heater of comparable output
- The COP this specific unit achieves at your conditions
- Compressor and control-board longevity
- Noise at the distance your deck actually sits from it
These need a unit in hand across a season. We do not have one, so we do not have an opinion worth printing on them.
#ad We earn a commission if you buy through this link, at no extra cost to you. It never changes the ranking. How this site is funded. Prices last checked September 2, 2026.
SmartPool SunHeater S601P Solar Heating System
Solar panels that plumb into the return line and heat the water with sunlight rather than fuel, which puts their running cost at zero — the only entry in the whole heating category where that is true. The trade is that you cannot dial in a temperature: the panels deliver what the sun gives them on the day, and on a cloudy week they deliver very little.
Best for Adding real heat with no running cost, on a sunny site
| Type | Roof or ground-mounted solar collector panels, plumbed inlineThe manufacturer publishes no retrievable specification sheet; figure is as listed at retail. | Retail listing |
|---|---|---|
| Running cost | $0 in fuelThe circulation pump is already running for filtration. There is no additional fuel or electricity cost attributable to the heat. | Our arithmetic |
As much as 15 degrees F
Claimed by Bob Vila, describing the S601P. Conditions: Stated as requiring ample sunlight; no time period given. Source
Note the phrasing: with ample sunlight it can boost temperature by as much as 15 degrees. That is a cumulative ceiling reached over days of good sun, not a figure you will see in an afternoon.
- Zero fuel cost, forever — nothing else in this category can say that
- No combustion, no gas line, no additional electrical service
- Panels can be added to as the budget allows
- You get the sun's schedule, not yours
- Needs real unshaded mounting area, and plumbing work to install
- Does nothing on a cold cloudy week, which is when you most want it
- Actual heat output at your latitude, roof pitch and shading
- How the panel material survives a decade of UV and freeze cycles
- Whether the included fittings suit your existing plumbing
These need a unit in hand across a season. We do not have one, so we do not have an opinion worth printing on them.
#ad We earn a commission if you buy through this link, at no extra cost to you. It never changes the ranking. How this site is funded. Prices last checked September 2, 2026.
Sun2Solar 1200 Series Crystal Clear Solar Cover
The value pick, and the one whose logic actually holds up. A clear cover transmits more sunlight into the body of the pool instead of absorbing it at the surface, and 12 mil is the point where lifespan stops being the limiting factor. Bob Vila measured this and the 16-mil blue at the same 4 to 5 degrees in an hour, so you are paying less for the same measured result and giving up some years of service life.
Best for Most pools, most budgets — the default recommendation
| Thickness | 12 milThe manufacturer publishes no retrievable specification sheet; figure is as listed at retail. | Retail listing |
|---|---|---|
| Color | Clear | Retail listing |
| Stated lifespan | 3 to 4 years for the 12-mil clear tierSwim University's published figure for 12-mil clear covers generally. | Retail listing |
| Bubble side | Bubbles face the water | Published standard |
4 to 5 degrees F in one hour
Claimed by Bob Vila, measured across all covers in their group. Conditions: One hour under 2pm sun on 89 to 92 degree F days. Source
- Clear transmits more light into the water instead of stopping it at the surface
- 12 mil is the sweet spot: real service life without 16-mil bulk
- Cheaper than the 16-mil tier with no measured heating penalty
- Shorter published lifespan tier than 16 mil
- A clear cover shows algae and debris more obviously, which some people dislike
- Whether clear genuinely outlasts or under-lasts blue in the same thickness
- Real-world tear resistance at a pool with rough edges
- How much the clear material clouds over a season of UV
These need a unit in hand across a season. We do not have one, so we do not have an opinion worth printing on them.
#ad We earn a commission if you buy through this link, at no extra cost to you. It never changes the ranking. How this site is funded. Prices last checked September 2, 2026.
An electric resistance pool heater
Skip it for a full-size pool, and the arithmetic is not close. At the same electricity price, a resistance heater costs about five times what a heat pump costs to deliver the same heat, because it makes heat instead of moving it. It has a legitimate niche on a small above-ground pool or a spa where the volume is tiny and the install is a plug. On 20,000 gallons it is the most expensive way to heat water that exists.
Best for Spas and very small above-ground pools only
| Cost per million BTU delivered | About $53.75 at our published assumptionsUS average residential electricity at 18.34 cents/kWh (EIA, June 2026) at a coefficient of performance of 1.0. Compare with about $10.75 for a heat pump on the same electricity. | Our arithmetic |
|---|---|---|
| Efficiency | About 1:1 — no efficiency to argue about | Published standard |
- Cheap to buy and often just plugs in
- Genuinely sensible on a spa or a very small pool
- About five times a heat pump's running cost for identical heat
- Draws serious current, which frequently means an electrical upgrade
- On a full-size pool the running cost is punishing
- Element life in your water chemistry
- Whether your existing circuit can carry it
These need a unit in hand across a season. We do not have one, so we do not have an opinion worth printing on them.
#ad We earn a commission if you buy through this link, at no extra cost to you. It never changes the ranking. How this site is funded. Prices last checked September 2, 2026.
Questions people actually ask
How much does it cost to heat a pool?
Why does the calculator ask for coefficient of performance?
Where do the default energy prices come from?
- Average retail price of electricity to US residential customers: 18.34 cents/kWh, June 2026U.S. Energy Information Administration · read 2026-09-02
- US residential natural gas price: $24.09 per thousand cubic feet, June 2026U.S. Energy Information Administration · read 2026-09-02
- US residential propane price: $2.674 per gallon, week ending 30 March 2026U.S. Energy Information Administration · read 2026-09-02
- Energy content conversion factors: 3,412 BTU per kWh, 1,036 BTU per cubic foot of natural gas, 91,452 BTU per gallon of propaneU.S. Energy Information Administration · read 2026-09-02
- U.S. Department of Energy pool-energy figures (evaporation share, BTU per pound evaporated, cover savings, recommended temperatures, wind effect)Recreonics, reproducing and attributing the U.S. Department of Energy · read 2026-09-02
- Pool heater roundup: the 8.33 BTU per gallon per °F figure, attributed on the page to Alicia Toedter of Leslie'sBob Vila · read 2026-09-02
Every URL above was fetched and returned content on the date shown. Where a figure is ours rather than somebody else’s, the arithmetic is on the page and on the methodology page. If you find an error in it, we would genuinely like to know.
Read next
How much does it cost to heat a pool?
The complete cost model: what a million BTU costs to deliver with each fuel, what that means per degree and per pool size, and why heat-up cost is not your monthly bill.
What a pool heat pump costs to run
The heat pump running-cost derivation, what happens to it in cold air, and the two inputs that change the answer more than anything else.
Solar cover savings calculator
Turns your pool's overnight temperature drop into a saving per night, per season, and a payback period — the calculation nobody in this category publishes.
Heat pump vs gas pool heater
The two options priced per delivered BTU and timed on the same pool, with the one question that decides which trade suits you.
Pool heating time calculator
Enter your gallons, the rise you want and your heater's rating. Handles the gas-versus-heat-pump rating trap and prints the whole calculation.