The most efficient pool heaters
Ranked on what efficiency actually means for a pool heater, including the trap that makes the least efficient machine on the market look like the best.
Quick picks
Ranked on heat delivered per unit of energy bought, using published figures where a maker states one and our stated assumption where it does not. The skip entry is the most important row on the page.
| # | Product | Best for | Price |
|---|---|---|---|
| 1 |  Most efficient with a published number FibroPool FH255 55,000 BTU Pool Heat Pump A manufacturer-stated COP of 5.92 — the highest efficiency figure any maker on this site actually prints. | A smaller pool where a full-size heat pump is more machine than the water needs | |
| 2 |  Most efficient full-size class Hayward HeatPro Pool Heat Pump A heat pump in the 140,000 BTU/hr class. Run at an assumed COP of 5.0 because no figure is published. | Lowest running cost per degree when you want real temperature control | |
| 3 | No photo Infinite, technically SmartPool SunHeater S601P Solar Heating System No fuel in, heat out. Efficiency is not a meaningful number for solar, which is the point. | Adding real heat with no running cost, on a sunny site | |
| 4 |  Most efficient gas, on a stated figure Raypak Digital Natural Gas Pool Heater 82% printed in the listings. The best gas can do is deliver most of what it burns. | Heating fast and occasionally, rather than holding a temperature | |
| — | No photo The 100% trap An electric resistance pool heater Nearly 100% efficient and five times a heat pump's running cost. The rating and the bill point opposite ways. | 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 October 17, 2026.
What efficiency means for a pool heater, and why it is two numbers
Every pool heater has an efficiency, and the category quotes it in two incompatible units, which is why searching for the most efficient heater returns confident nonsense.
- Thermal efficiency, a percentage, is what gas heaters quote. It is the share of the fuel’s energy that reaches the water. A figure of 82% means 18% goes up the flue. It cannot exceed 100%.
- Coefficient of performance, a ratio, is what heat pumps quote. It is the heat delivered divided by the electricity drawn. A COP of 5.0 means five units of heat for one unit of electricity, because the machine is moving heat from the air rather than making it. It routinely exceeds 100% — that is the entire point of a heat pump.
Put both on the same scale — heat delivered per unit of energy bought — and the ranking is not close:
| Heater type | Rated as | Heat out per unit in | Cost per million BTU |
|---|---|---|---|
| Solar panels | Not rated | No energy bought | $0.00 |
| Electric heat pump | COP 5.0 (assumed) | 5.0 | $10.75 |
| Natural gas | 82% thermal | 0.82 | $28.36 |
| Propane | 82% thermal | 0.82 | $35.66 |
| Electric resistance | About 100% | 1.0 | $53.75 |
The last two columns do not rank the same way, and that is the finding. Cost depends on the fuel price as well as the efficiency, which is why the cost column is the one that decides a purchase. The derivation.
The 100% trap
Heat pumps: efficient, and mostly unquantified
Heat pumps are the most efficient controllable heaters by a wide margin, and the frustrating thing about ranking them is that most makers do not publish the number. Of the heat pumps on this site, two do: the FibroPool FH255 at 5.92, and AquaCal’s HeatWave SuperQuiet at 5.7 — and only the AquaCal figure comes with the condition it was measured at, the AHRI standard 80°F air, 80°F water and 80% humidity. That condition is what makes a COP mean anything. The Hayward and Raypak full-size units describe their efficiency in words in the listings we read, and we run those at a conservative 5.0.
Two things to know about any COP figure. It is measured at warm air temperature, and it falls as the air cools, so the rated number is a best case rather than a season average. And figures of 15 or more, which appear on some import listings, are not credible for a residential pool heat pump under normal conditions and should be read as marketing. What happens to the COP in cold air works the fade through in dollars.
Gas: the ceiling is close, and the differences are small
A gas heater cannot beat 100% and the good ones sit in the low 80s. Raypak states 82% in its listings; neither Hayward’s current H-Series W3HS150FDN nor Pentair’s MasterTemp publishes a percentage, so we run both at the same 82%. A point or two either way on a full-size heat-up is a couple of dollars, inside the noise of your own gas rate.
So “most efficient gas heater” is a real question with a small answer. Buy the one whose maker states a figure, size it to your gas line rather than to the biggest number, and accept that no gas heater will approach a heat pump on running cost. The gas roundup ranks them on what is published.
The 2028 federal standard
The Department of Energy has amended its energy conservation standards for consumer pool heaters, with compliance required from 30 May 2028. The practical effect is a higher efficiency floor for what can be sold after that date. It does not change the physics above: a compliant gas heater is still a gas heater, and a compliant heat pump still moves heat rather than making it. If you are on the fence, two swimming seasons without heat costs more than the efficiency gain is likely to be worth — and a cover is the better use of the interval.
Two follow-ons. Which manufacturers publish an efficiency figure at all is itself a way to choose between them, and our brand comparison sorts them on exactly that. And efficiency is only half of running cost over a decade — the other half is how long the machine lasts, which turns on a component you pick at purchase.
The efficiency nobody rates: not losing the heat
Every heater on this page is rated on how well it adds heat. The pool is losing it continuously, and the Department of Energy puts about 70% of that loss on evaporation. A cover on the water at night is not a heater and has no efficiency rating, and it saves 50 to 70% of heating cost by DOE’s figure — more than the gap between the best and worst gas heater, and more than the gap between a rated and an unrated heat pump. The most efficient pool heating setup is a smaller heater and a cover, not a bigger heater. The cover picks, and the ranked picks across every heater type on the cost basis that this page argues for.
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.
FibroPool FH255 55,000 BTU Pool Heat Pump
The heat pump worth looking at when a full-size one is more machine than the pool needs. FibroPool publishes 55,000 BTU/hr of output and a rated COP of 5.92, which is above the 5.0 we assume for heat pumps generally — so on the pool sizes the manufacturer actually names, the running cost lands below the category figure. The catch is the other side of the same number: 55,000 BTU/hr is not much heat, and on a pool larger than FibroPool lists it will run all day and never catch up.
Best for A smaller pool where a full-size heat pump is more machine than the water needs
| Rated output | 55,000 BTU/hrPublished as OUTPUT, which is the heat-pump convention. It is not comparable with a gas heater's input rating. | Manufacturer |
|---|---|---|
| Pool sizes the manufacturer names | Above-ground up to 21 ft round or 15 x 30 ft oval; inground up to 10,000 gallons | Manufacturer |
| Supply | 240 V | Manufacturer |
| Rated COP | 5.92FibroPool words this as 5.92 times the heat for every dollar of electricity. The conditions it was rated under are not published, and a heat pump's COP falls as the air cools, so read it as a best case rather than a season average. | Manufacturer |
| Cost per million BTU delivered | About $9.08 at the published COPUS average residential electricity at 18.34 cents/kWh (EIA, June 2026) divided by the published COP of 5.92. At the more conservative COP of 5.0 we use across the site it comes out at about $10.75. | Our arithmetic |
- A published COP of 5.92, above the 5.0 we assume for the category
- All electric — no gas line, no flue, no combustion air to arrange
- Sized and priced for pools that a full-size heat pump is wasted on
- 55,000 BTU/hr is modest: about 30 hours to lift 20,000 gallons ten degrees
- Wants a dedicated 240 V circuit, which is an electrician's visit if you do not have one
- Like every heat pump, it fades as the air cools — the shoulder season you bought it for
- The COP this unit reaches at your air temperature and humidity
- Compressor and control-board life, which decides whether a cheaper heat pump is a bargain
- How loud it is 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 October 17, 2026.
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 October 17, 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, rack or ground-mounted solar collector panels, plumbed inline | Manufacturer |
|---|---|---|
| Collector area | Two 2 x 20 ft panels, 80 sq ft totalThis is the number to size from. The trade rule of thumb is collector area equal to 50-100% of the pool's surface, so a 16 x 32 pool needs several of these systems rather than one. | Manufacturer |
| Material | Polypropylene, stated not to corrode or scale | Manufacturer |
| Also required | One SK21 System Installation Kit per installation, sold separatelyThe manufacturer's own wording. One SK21 serves up to four of these two-panel systems. The panels on their own are not a complete installation, which is the commonest surprise in this product category. | Manufacturer |
| 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 |
Up to 6 to 10 degrees F
Claimed by SunHeater, on its own product page for the S601P. Conditions: Stated as under favorable conditions; no time period given. Source
Worth reading beside the figure below. The manufacturer's own claim for this product is 6 to 10 degrees. The retail listings for the same model say up to 15. The larger number is the one further from the manufacturer.
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 October 17, 2026.
Raypak Digital Natural Gas Pool Heater
The right answer when speed matters more than running cost — a weekend pool you want warm on Friday afternoon rather than one you hold at temperature all season. At the assumptions we publish, gas costs roughly two and a half times what a heat pump costs per delivered BTU, and it will get there in a fifth of the time. Buy the speed if you need the speed.
Best for Heating fast and occasionally, rather than holding a temperature
| Type | Natural gas or propane fired, digital controlThe manufacturer publishes no retrievable specification sheet; figure is as listed at retail. | Retail listing |
|---|---|---|
| Rating convention | Rated by BTU/hr INPUTA 400,000 BTU gas heater burns 400,000 BTU an hour and delivers roughly 82% of it. Do not compare that number directly against a heat pump's output rating. | Published standard |
| Cost per million BTU delivered | About $28.36 at our published assumptionsUS average residential natural gas at $24.09/Mcf (EIA, June 2026) and an assumed 82% thermal efficiency. | Our arithmetic |
- Fast — hours rather than most of a day on a full-size pool
- Works the same in cold air, unlike a heat pump
- Lower purchase price than a heat pump of equivalent real output
- Roughly two and a half times a heat pump's cost per delivered BTU
- Needs a gas line sized for it, which is often the real cost
- Propane instead of natural gas raises the running cost by about a quarter again
- The efficiency this specific unit achieves in service
- Heat exchanger life against your water chemistry
- Whether your existing gas supply can feed it without an upgrade
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 October 17, 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 October 17, 2026.
Questions people actually ask
What is the most efficient type of pool heater?
Is a 100% efficient pool heater the best?
What is a good COP for a pool heat pump?
Which is more efficient, a gas or electric pool heater?
- 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
- Federal energy conservation standards for consumer pool heaters (10 CFR 430.32(k); amended by 88 FR 34624, compliance required from 30 May 2028)U.S. Department of Energy, Building Technologies Office · 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
Pool heater brands, compared
Hayward, Pentair, Raypak, Jandy, AquaCal and FibroPool at brand level: what each builds, what each publishes, and which to shortlist.
AquaCal HeatWave SuperQuiet review
AquaCal's SuperQuiet line on the record: a published COP of 5.7 at a summer test condition, a titanium exchanger, a narrow flow window, and less heat per hour than the two full-size rivals this site already ranks.
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.
Pool heat pumps worth buying
Full-size and small heat pumps ranked on published output, exchanger material and what the manufacturer will actually say about efficiency. With the sizing math for your pool.
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.
Electric pool heaters
Heat pump or resistance element? Both are sold as electric pool heaters and one costs five times what the other does to deliver the same heat. How to tell which is which before you buy.
Is a pool heater worth it?
The pre-purchase doubt, answered with arithmetic: what a heater costs to run per week of swimming you actually gain, when the honest answer is no, and the cheaper thing to try first.