The best pool heaters for inground pools come down to two questions: how fast do you need the water to warm up, and how much do you want to spend running it every month. A gas pool heater burns fuel and can lift a large pool several degrees an hour. A heat pump pool heater pulls heat out of the outside air, so it costs far less to run but works much more slowly. Solar panels only do what the sun allows.
Most inground pool owners end up in one of those three camps, and the wrong pick shows up as a bill you did not expect. Below we compare eight heaters across gas, inverter heat pump, and large-capacity inverter categories, with the noise, BTU rating, warranty, and connection details that actually change how they perform on a real pool.
Three details decide most of these purchases: your pool volume in gallons, the coldest night your climate actually reaches, and whether a natural gas line is already at the equipment pad. Get those right and the choice narrows fast. If you want a starting point before you read further, our notes on keeping a room warm efficiently cover the same heat-loss thinking that applies to a pool, just at a smaller scale.
Table of Contents
Top 3 Inground Pool Heater Picks in 2026
Three picks cover most inground pool situations. The AQUASTRONG HEX100 leads on measured efficiency and the deepest owner feedback in this group, the Raypak handles fast heat-up on gas, and the Hayward covers smaller pools without over-sizing the burner.
AQUASTRONG HEX100
- 15.8 COP inverter efficiency
- Heats and cools in one unit
- 55 dB operation
Hayward H-Series 150K
- 150
- 000 BTU natural gas
- Digital LED self-diagnostics
- Low-NOx certified
Best Pool Heaters for Inground Pools in 2026 at a Glance
Every heater below is sized for an inground pool, and the list mixes two gas units with six inverter heat pumps so the tradeoffs stay visible. Gas gives speed; inverter heat pumps give lower running cost and quieter operation.
| Product | Specs | Action |
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| AQUASTRONG HEX100 Inverter Pool Heat Pump |
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 Raypak 266,000 BTU Digital Gas Pool Heater |
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| Hayward H-Series 150,000 BTU Gas Heater |
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 VARMINPOOL 105,000 BTU Inverter Heat Pump |
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 Varpoolfaye 120,000 BTU Inverter Heat Pump |
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 WARMBLU 28000 Gallon Inverter Heat Pump |
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 MICOE 100,000 BTU Inverter Pool Heat Pump |
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 Varpoolfaye 140,000 BTU Inverter Heat Pump |
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What Type of Pool Heater Is Best for an Inground Pool?
A gas pool heater is best if you want fast, on-demand heat and already have a gas line at the pad. A heat pump is best if you want to hold a temperature for hours a day without a large fuel bill. A solar heater is best as a supplement in a sunny climate, never as the only source of heat.
Here is how the four practical types compare. The gas numbers describe fuel input, while the heat pump numbers describe heat moved into the water, so the two BTU figures are not directly comparable.
Natural gas and propane heaters. These burn fuel to heat water passing through a copper or cupro-nickel heat exchanger. Reviewers on r/pools put the tradeoff plainly: a heat pump is roughly one quarter the heat output of a 400,000 BTU gas unit, so gas wins on speed by a wide margin. The Raypak in this group is rated at 266,000 BTU, and owners report about 3 degrees per hour with good water flow.
Inverter heat pumps. These move heat from outside air into the pool using a refrigerant cycle, and a COP of 12 or higher means each watt of electricity delivers roughly 12 watts worth of heat. The COP figures here run from 12.3 to 16.0, which is where the low running cost comes from. Inverter compressors ramp up and down instead of switching fully on and off, which is also why the dB ratings are as low as 43.
Solar heaters. Water circulates through sun-warmed tubes on the roof. Solar is free to run and adds a few degrees on a sunny day, but it does nothing at night or through a cold stretch. Owners on r/swimmingpools who added solar usually paired it with a cover they could leave closed, which is what makes it worth the roof space.
Electric resistance heaters. These are simple and cheap to buy, but they put every unit of heat on the meter, so running cost is dramatically higher than an inverter heat pump at the same output. For a full-size inground pool this is rarely the sensible route.
Match the type to your coldest nights rather than your average. In a climate where summer nights sit in the low 60s, a heat pump runs close to its rated COP all season. In a climate with hard freezes, owners on r/heatpumps warn that a heat pump does very little once the water approaches freezing, and a gas heater becomes the practical backup even if it only runs a handful of times a year.
One more decision input often gets skipped: whether a natural gas line already runs to the equipment pad. If it does, gas is far easier to add. If it does not, running a new gas line and getting the permit can cost more than the heater itself, and that calculation pushes most owners toward a heat pump.
1. AQUASTRONG HEX100: Best Overall Inverter Pool Heat Pump
Swimming Pool Heater for Above Ground and Inground Pool 20’*43’*48″
Full DC inverter with 15.8 COP
Heats 47-104F, cools 47-83F
Defrost every 40 min
116.8 lb unit
Pros
- 15.8 COP inverter efficiency
- Heats and cools in one unit
- 55 dB operation with app scheduling
- Three connection options for different plumbing
Cons
- 116.8 pound weight makes placement a two-person job
- Defrost pauses heating about every 40 minutes
- 3-year warranty is short for a heat pump
The HEX100 is the model I would put in front of most inground pool owners. It is a full DC variable frequency inverter with a listed COP of 15.8, which puts it at the top of this group alongside the WARMBLU. It heats and cools in the same cabinet, and the listing rates it for pools up to 20 feet by 43 feet by 48 inches deep.
Owner feedback is the strongest evidence here. This unit carries 534 reviews at a 4.3 average, far more than any other heater on this list, and the pattern in those reviews is consistent. People like the combination of efficiency, quiet running, and app-based control, and the dual heating and cooling mode gets called out specifically.
Spec-wise, the numbers line up with what owners report. The heating range is 47F to 104F and the cooling range is 47F to 83F. Noise is listed as low as 55 dB, which sits in the middle of the heat pumps here rather than at the quiet end. The cabinet measures 39 by 17.32 by 25.6 inches and the unit weighs 116.8 pounds.
One detail worth planning for is the defrost cycle. It runs automatically every 40 minutes and lasts about five minutes, so heating pauses on a regular rhythm. Owners describe this as a short interruption rather than a failure, but it does mean the unit is not running flat out continuously.
Who the AQUASTRONG HEX100 suits
This is the right pick for a mainstream inground pool in a climate that gets cold but not consistently freezing. If you want one box to handle both heating in spring and cooling an overheated pool in August, the dual mode removes a second purchase decision.
It also suits anyone who would rather not touch a gas line. The app plus on-panel scheduling means you can start it before you get out of bed, and for owners with steady daily use, a COP of 15.8 is where the low running cost comes from.
Where it falls short
The 116.8 pound weight is manageable for two people but not one, and placement beside the equipment pad often means navigating a narrow side yard. Plan the path before the unit arrives.
The 3-year warranty is short compared with dealer lines that carry much longer compressor and heat exchanger coverage, so this is worth factoring in if you plan to run the heater for a decade.
2. Raypak P-R266A-EN-C: Best Gas Pool Heater for Fast Heat-Up
Raypak 266,000 BTU Digital Electronic Ignition Natural Gas Pool Heater
266,000 BTU natural gas
Digital spark ignition
About 3 degrees per hour
210 lb, 3/4 inch gas line
Pros
- Around 3 degrees per hour with good flow
- Cabinet does not retain heat after shutdown
- Digital ignition with pilot safety controls
- Parts are widely available
Cons
- Needs a 3/4 inch gas line and pro install for warranty
- Some units report sensor or board failure after about 18 months
- 210 pounds needs two people to move
If the pool needs to be warm today, the Raypak is the honest answer. At 266,000 BTU it is the largest output in this group, and owners consistently report a temperature rise of about 3 degrees per hour when water flow is right. That is the difference between swimming this afternoon and tomorrow.
Ignition is digital electronic intermittent spark with pilot safety controls, and the pilot only lights on a call for heat. The cabinet is described as not retaining residual heat after shutdown, which means it does not need a metal heat sink to stay safe near a wall or a wood fence.
Installation feedback is good for anyone replacing an existing unit. Owners say it matched existing plumbing and electrical connections, and experienced DIYers report getting it plumbed in without drama. Internals are accessible for troubleshooting and parts are easy to source, which matters a decade into ownership.
There is one plumbing quirk to know about. The inlet and outlet sit close together, so the loop needs a bypass setup with extra elbows rather than a simple straight run. Good installers plan for that up front.
Who the Raypak suits
This is the pick for cold-climate owners, swim-spa users, and anyone who wants a genuinely fast temperature rise. A spa or cold plunge that needs to hit temperature in an hour is the clearest case, because a heat pump cannot do that job.
It also makes sense as a secondary heater alongside a heat pump. Owners in mixed climates use the heat pump day to day and let gas handle the shoulder-season pushes and the cold snaps where a heat pump loses efficiency.
Where it falls short
The unit weighs 210 pounds, so moving it into place takes at least two people. More importantly, the warranty coverage depends on professional installation, and owners report that warranty service is difficult to obtain for DIY installers. If you plan to install it yourself, factor that into the decision.
A recurring complaint in the reviews is a temperature sensor or main board failure after roughly a year and a half. That is not early enough to call a defect, but it is the failure mode to keep in mind for budgeting repairs on a decade-old gas unit.
3. Hayward H-Series W3H150FDN: Best for Pools Up to 450 Square Feet
Hayward H-Series Natural Gas Pool Heater for Inground Pools 150,000 BTU
150,000 BTU natural gas
Covers pools up to 450 sq ft
Digital LED diagnostics
Low-NOx, 150 lb unit
Pros
- Digital LED panel with self-diagnostics
- Low-NOx certified for lower emissions
- Gas and electric hookups on either side
- Corrosion protection against unbalanced chemistry
Cons
- 150000 BTU is the smallest H-Series capacity
- LED panel takes practice to read
- Larger pools need a higher model
The Hayward H-Series at 150,000 BTU is sized for inground pools up to 450 square feet, and that is exactly the kind of match that gets overlooked. Too many buyers size up out of habit, then run a burner that is larger than the pool needs and pay for it every month.
Its control panel is an inground-specific design with a digital LED display and self-diagnostic performance monitoring. When something is off, the panel reports it rather than leaving you guessing, and the design is intended to reduce pump run time for energy savings.
Installation is straightforward by design. There is a built-in 3/4 inch gas connection, and both gas and electrical connections can be made on either side, so the unit fits into a tight pad without moving the whole run. The heater is low-NOx certified, which matters if emissions rules are tightening in your area.
Water chemistry gets attention too. The design includes corrosion protection against unbalanced water chemistry, which is the main reason heat exchangers fail early in real pools, particularly with a salt chlorine generator or high chlorine levels.
Who the Hayward H-Series suits
This is the pick for a smaller inground pool, roughly up to 450 square feet of surface, where a 400,000 BTU burner would simply be oversized. Owners tend to be satisfied once they size it correctly, and the review pattern reflects that.
It also fits anyone who wants a gas heater with a proper digital panel and self-diagnostics rather than a manual dial. The other H-Series models in this family cover 600, 750, and 1200 square foot pools and spas, so the same brand scales up if your pool is larger.
Where it falls short
At 150,000 BTU this is the smallest capacity in the lineup, so it is the wrong pick for a large deep pool or a swim spa. Check your square footage before ordering rather than assuming the brand name covers it.
The digital LED panel takes some getting used to. Owners who interpret the diagnostic readings correctly are happy; those who expect a simple thermostat sometimes find the readings confusing at first.
4. VARMINPOOL KSPF-030L1VUA3: Quietest Heat Pump at 43 dB
VARMINPOOL Swimming Pool Heater for Inground Pool 105000BTU
105,000 BTU for pools up to 30000 gal
43 dB minimum noise
Heats and cools
176 lb unit
Pros
- 43 dB is the quietest in this lineup
- 105000 BTU for pools up to 30000 gallons
- WiFi app with touchscreen and built-in timer
- Heats and cools in one unit
Cons
- Heating speed varies with weather and cover use
- Needs clear airflow around the unit
- 176 pounds is a two-person move
Noise is the reason to look at this one first. The VARMINPOOL runs as low as 43 dB, which is the lowest figure of any unit in this roundup and quiet enough to place next to a house wall or a covered patio without being a nuisance. Several other heat pumps here sit at 47 dB and the gas units are not in the same conversation at all.
Capacity is 105,000 BTU, and the listing rates it for above ground and inground pools up to 30000 gallons. That is a genuinely large pool for a heat pump, which matters because most buyers underestimate how much capacity they need for a big body of water.
Control is handled three ways, which is unusual at this level. You get a smart WiFi app, a touchscreen panel on the unit, and a built-in timer, so scheduling works whether or not you want to pull out your phone. The housing is described as weather-resistant for outdoor installation.
The honest caveat in the reviews is speed. Owners are clear that performance depends heavily on pool size, outdoor temperature, circulation time, and cover use. That is true of every heat pump, but on a 30000 gallon pool the effect is easy to feel.
Who the VARMINPOOL suits
This is the pick for a large inground pool where the heater has to sit close to living space. At 43 dB it is the option for owners whose equipment pad is beside a bedroom window, a patio, or a neighbor’s fence line.
It also suits anyone planning to run the unit on a schedule rather than continuously. The built-in timer and app let you run it overnight or during the coldest part of the day, which is where a heat pump’s efficiency actually pays off.
Where it falls short
Expect a multi-day heat-up on a pool at the top of its range. The reviews are consistent that results depend on circulation time and cover use, so pair this with a solar cover and accept that reaching temperature is a project rather than an event.
Airflow clearance is not optional. The weather-resistant housing still needs open space around the unit, and in a cramped side yard that constraint can rule it out. Measure the pad before you commit.
5. Varpoolfaye KSPF-007L1MR1A2: Best Heat Pump for Saltwater Pools
Varpoolfaye 120,000 Btu Inverter Pool Heat Pump for Inground Pools 220V
120,000 BTU, COP of 12.3
47 dB operation
Fresh and salt water rated
Pools up to 33000 gallons
Pros
- COP of 12.3 at 47 dB
- Rated for freshwater and saltwater pools
- Works with standard 1.5-inch connectors
- Includes 118-inch power cord
Cons
- Factory adapters can leak at first startup
- App is less capable than the on-unit panel
- Cold-weather freeze-ups reported on some units
Salt water is harder on pool equipment than chlorine, so the heat exchanger material matters more than it does for a conventional pool. This Varpoolfaye is listed for both freshwater and saltwater use, and it pairs that with a COP of 12.3 and 120,000 BTU of heating output.
Owners report a temperature rise of about 1 to 3 degrees per hour of operation, which is a realistic figure for a heat pump in normal conditions. Several reviews specifically confirm that both the heating and chiller modes work in real pools rather than only on paper.
Setup is the easiest part. The package includes 1.5-inch connectors and a 118-inch power cord, and the water-electric separation design keeps the electrical compartment away from the wet side. The unit runs at 47 dB and has inverter mode with an intelligent touch control panel plus one-button fast heat.
Support is worth calling out. Multiple reviews mention that customer service sends replacement parts quickly, and one describes a same-day fix that avoided a return. On a marketplace-brand unit, that kind of responsiveness is a bigger deal than the spec sheet suggests.
Who the Varpoolfaye 120,000 BTU suits
This is the pick for a saltwater inground pool in a moderate climate, especially if the equipment pad is close to the house. Freshwater and saltwater compatibility in the same listing removes the guesswork about exchanger material.
It also suits owners who want app control without giving up local control. The touch panel handles day-to-day settings and the app covers scheduling and mode switching, so a phone glitch is not a reason to stop heating the pool.
Where it falls short
Some units report freezing up in cold weather and stopping until relays are swapped, and heating in cold climates can take multiple days on a large pool. If your winters are hard, treat this as a shoulder-season unit rather than a deep-winter solution.
The factory-installed water adapters can leak at first startup and may need thread sealant and extra torque. Budget an hour with a wrench before the first run rather than discovering it in the yard. At 238 pounds, plan for a two-person move.
6. WARMBLU KSPF-030L1VUA2: Highest COP and a Titanium Heat Exchanger
WARMBLU 28,000 Gallons Inverter Pool Heat Pump for Inground Pools 220V
COP 16.0, titanium exchanger
Pools up to 28000 gallons
Sub-50 dB
Draws about 6 amps heating
Pros
- COP up to 16.0 with a titanium heat exchanger
- Draws about 6 amps while running
- 20+ degree rise in about 24 hours in mild climates
- Sub-50 dB quieter than a refrigerator
Cons
- 199.6 pounds needs two people
- Heating a pool takes a couple of days
- Smart Life app pairing is confusing
The WARMBLU posts the highest COP figure in this roundup at 16.0, and it gets there through the SpringBreath 1.0 heating system with a pure titanium heat exchanger. A higher COP means more heat per watt of electricity, which is the single biggest driver of long-term running cost on a heat pump.
Capacity is rated for pools up to 28000 gallons, which puts it in the same class as the larger units here. Owners report a temperature rise of 20 or more degrees in about 24 hours in mild climates, which is a genuinely good result for a heat pump on a pool of that size.
The electrical draw is the number to look at. Reviews describe the unit pulling about 6 amps, roughly 1300 watts while running, which is roughly what a dehumidifier or a medium window air conditioner pulls. That is the mechanical reason the running cost stays low compared with gas.
Noise is listed as sub-50 dB and owners describe it as quieter than a standard refrigerator. The inverter control uses an intelligent chip and a dynamic algorithm, and control comes from a mobile app or a modern touch panel. Water and electrical components are fully separated for what the maker calls industrial-grade safety.
Who the WARMBLU suits
This is the pick for an owner whose priority is the lowest possible running cost on a large pool. At 28000 gallons of rated capacity and a COP of 16.0, it is a good match for a big body of water that needs steady temperature maintenance rather than quick warm-ups.
It also suits anyone who wants a titanium heat exchanger. Titanium resists corrosion better than copper or cupro-nickel, which matters in a pool with a salt chlorine generator or aggressive sanitizer levels.
Where it falls short
The warranty is the weakest of the inverter group at 12 months, though lifetime customer support, tutorial manuals, and a user community are included. On a unit this size, a longer parts warranty would be more reassuring.
Owners still describe a couple of days to heat a large pool and say a solar cover is needed to hold temperature afterward. Two people are needed to move the 199.6 pound unit, and the Smart Life app setup is confusing because you have to connect your phone to the heater network first. Some units have arrived with a broken fan blade.
7. MICOE MSHP-030Y1: Best Warranty and Support Package
MICOE 100,000 BTU Inverter Pool Heat Pump for 26,000 Gallon Pools
100,000 BTU, pools up to 26000 gal
Titanium exchanger
54 dB, 2-year parts warranty
Pros
- 2-year parts replacement warranty with 24/7 live chat
- Up to 100000 BTU for pools up to 26000 gallons
- Titanium heat exchanger with IPX4 cabinet
- App can auto-start on pump line pressure
Cons
- About 3 days to go from 68F to 80F in cool nights
- 50-amp circuit can mean a significant daily cost
- Confusing wiring diagrams
- Some units arrive with a dead touchscreen
The MICOE is the pick when warranty and support matter more than raw numbers. It carries a 2-year parts replacement warranty with 24/7 live-chat support, which is the longest coverage commitment of the inverter heat pumps in this group, and the reviews describe that support as unusually responsive.
Capacity is up to 100,000 BTU for above ground and inground pools up to 26000 gallons. The heating range is 46F to 104F and the cooling range is 45F to 82F, with automatic defrost for cooler conditions. The heat exchanger is titanium and the cabinet is an IPX4-rated, UV-resistant ABS.
One app feature stands out. The unit can be set to start automatically when the pump establishes line pressure, so the heater comes on by itself with circulation rather than needing a separate schedule. Owners mention this works well in practice and removes a step from daily use.
Reported heat-up performance is the honest drawback. Owners describe about 3 days to move a pool from 68F to 80F when the nights are cool, which is consistent with a 100,000 BTU heat pump on a mid-size pool. One owner verified the unit holding a pool in the mid-to-high 80s, which is the steady-state result that matters.
Who the MICOE suits
This is the pick for an owner who wants a warranty that is easy to lean on, and for anyone who is not comfortable with electrical documentation. Reviews specifically mention fast, clear answers to electrical and plumbing questions, and one describes a replacement grounding part sent out at no charge.
It also suits owners who prefer holding a set temperature rather than heating on demand. A quiet 54 dB variable-speed compressor running steadily is a better experience than an intermittent big-output unit cycling hard.
Where it falls short
It is slower than older high-BTU gas units, and the reviews are candid about three-day heat-ups in cool conditions. It is also the smallest-rated pick we do not recommend for very large pools, at 100,000 BTU and a 26000 gallon ceiling.
The 50-amp circuit can mean a meaningful daily running cost, and the wiring diagrams are confusing with a flimsy terminal block cover plate. Some units have arrived with a non-functional touchscreen, and the wired remote is not meant for daily use. At 220 pounds, plan for two people.
8. Varpoolfaye KSPF-010L1UR1A2: Highest Output for Very Large Pools
Varpoolfaye 140000BTU Swimming Pool Heat Pumps Up to 42000 Gallons 220v
140,000 BTU heating capacity
COP of 12.8 at 47 dB
Pools up to 42000 gallons
337 lb unit
Pros
- 140000 BTU for pools up to 42000 gallons
- Highest capacity among the inverter units here
- COP of 12.8 at 47 dB
- Works with freshwater and saltwater
Cons
- 337 pounds makes placement a two-person-plus job
- Condensation drips from the unit during heating and defrost
- 59 reviews is the thinnest owner history here
This is the largest heat pump in the group at 140,000 BTU, rated for pools up to 42000 gallons. For a very large inground pool, a 100,000 BTU unit is genuinely undersized, and this is the option that closes that gap without going to gas.
It also holds the highest average rating of the pool heat pumps we analyzed at 4.7. Owners cite strong heating output, low noise at 47 dB, and app-based control. The COP of 12.8 is slightly below the WARMBLU and AQUASTRONG figures, so it trades a little efficiency for a lot of capacity.
Freshwater and saltwater are both supported, the unit runs on 220V inverter mode with an upgraded intelligent control panel, and WiFi app control handles temperature, scheduling, and mode switching. The package includes 1.5-inch connectors, so the plumbing hookup is straightforward.
The practical drawback is weight. At 337 pounds this is by far the heaviest unit here, and getting it onto a pad through a side yard is a genuine logistics problem. Owners also note that condensation drips from the unit during heating and defrost cycles, which is normal but needs a clear spot to drain.
Who the Varpoolfaye 140,000 BTU suits
This is the pick for owners of very large inground pools in the 30000 to 42000 gallon range who want to stay with a heat pump. Very few heat pumps reach that ceiling, and sizing down means accepting a heat-up that never really finishes.
It also suits anyone who wants capacity headroom. A unit rated at the top of its range handles a covered pool, mild weather, and a set temperature more comfortably than one sized to the minimum.
Where it falls short
Weight is the dealbreaker for many installations. At 337 pounds, plan for professional delivery and a crew, and measure every gate and turn on the route to the pad before ordering.
The owner history is the thinnest of the group at 59 reviews, so there is less long-term data to lean on than with the AQUASTRONG or Hayward. Condensate management around the unit is a small but permanent piece of site planning.
How to Size a Pool Heater for Your Pool Volume
Size to your pool and your coldest nights, not to the largest number you can find. Owners are routinely advised to buy the biggest BTU unit available, and that advice produces oversized burners and undersized heat pumps at the same time.
Step one: get your pool volume in gallons. For a rectangular pool, multiply length times width times average depth in feet, then multiply by 7.5. A 16 by 32 foot pool with an average depth of 5 feet gives 2560 cubic feet, or about 19200 gallons. Irregular shapes need a more careful estimate, so measure rather than guess.
Step two: pick a target temperature rise and a realistic heat-up time. Most people want to go from a no-heat 68F to about 80F, which is a 12 degree rise. Decide honestly whether you want that in one evening or over a weekend, because that single decision separates gas from heat pump more than any other.
Step three: match the capacity class to the goal. For gas, the input rating in BTU per hour is the meaningful number. For a heat pump, the output BTU and the COP are what matter, and the two figures are not comparable. A 150,000 BTU gas heater and a 150,000 BTU heat pump do very different amounts of work.
A rough reference for pools is worth having in your head. Under 10000 gallons, most 100,000 BTU heat pumps handle a comfortable season. Between 10000 and 20000 gallons, look at 120,000 BTU or larger. Above 20000 gallons, you are in the 140,000 BTU class or the gas range. These are starting points, not rules.
The common sizing error runs in the opposite direction too. Oversizing a gas heater means paying for unused capacity every time the burner fires, and starting and stopping cycles shorten burner life. An undersized heat pump simply never reaches temperature on a cold week, which is a recurring frustration owners report on r/pools.
There is a rule of thumb in the pool heat pump trade sometimes called the 20 rule: roughly 20,000 BTU of heat pump capacity for a 20000 gallon pool, adjusted for climate and how quickly you want the water warm. Treat it as a starting point for a moderate climate and move up or down from there based on your coldest nights and your cover situation.
Before you finalize any size, reduce the work the heater has to do. A pool cover is the cheapest efficiency upgrade available. Owners who pair solar heating with a cover they can leave closed get meaningfully better results, and every heat pump in this roundup performs better under a cover because the heat stops escaping at the surface.
What a Pool Heater Costs to Run Each Month
Running cost is where gas and heat pump separate so clearly that the comparison is not close. Rather than quote a number that changes with your utility rate, here is how each type scales so you can plug in your own bill.
Heat pumps. The clearest figure in the product data comes from the WARMBLU reviews, where owners describe the unit drawing about 6 amps, roughly 1300 watts, while running. A 1300 watt load is comparable to a dehumidifier or a medium window air conditioner, which is why heat pump owners describe their heating costs as unremarkable. The COP figures here, from 12.3 to 16.0, mean each watt of electricity delivers 12 to 16 watts worth of heat.
Gas. Cost scales directly with fuel burned, so the 266,000 BTU Raypak running at about 3 degrees per hour on a 19200 gallon pool is using fuel continuously while it heats. A pool brought up 12 degrees is a large amount of energy no matter how efficient the burner is, and that is why gas is framed as a speed purchase rather than a maintenance purchase.
Owners on r/pools anchor the two experiences in practical terms. A heat pump owner describes heating the pool for a few hours on a small budget, while gas users consistently describe the burner running for extended stretches to do the same job. Multiple forum threads ask the same question, which is why we are laying out the method here rather than a single figure.
Two habits change the answer more than any heater choice. Running the heater only when the circulation pump is already turning avoids paying to heat a static pool, and scheduling heat pump runtime for the coldest hours of the day raises the ambient air temperature the unit draws from, which lifts COP exactly when you need it.
Our broader note on picking hardware that fits the job makes the same point about matching capacity to real workload. A heater sized for your actual pool volume beats a bigger unit every time, on cost and on longevity.
Installation, Maintenance and Lifespan
Every heater on this list is plumbed into the same place, between the filter and the rest of the equipment, and the loop is the part that matters. A bypass assembly lets you isolate the heater for service without shutting down the whole pool, and it is the single most useful thing to have installed even if you do not think you will ever need it.
Gas units. These need a 3/4 inch gas line at minimum, and both gas heaters here specify that. A permit and a licensed gas fitter are effectively required, and the Raypak warranty depends on professional installation. The Hayward makes this easier with a built-in 3/4 inch connection and gas and electrical hookups available on either side.
Heat pumps. These need 220V power, correct water flow through the unit, and open airflow clearance around the cabinet. The connectors are the easy part: several units here include 1.5-inch fittings, and the AQUASTRONG offers three connection options including 1.25 inch and 1.5 inch hose adapters. Budget time for the first startup, since factory adapters can need extra torque or sealant.
Annual maintenance. For gas, clean the burner and check the flue and gas connections annually before the season, and treat the temperature sensor and control board as known long-term wear items to budget for. For heat pumps, rinse the coil or keep airflow clear of leaves and debris, confirm the defrost cycle is running, and check the water chemistry that touches the exchanger.
Water chemistry is the lifespan variable. The reviews on the Hayward call out corrosion protection against unbalanced chemistry, and this is the honest answer to how long any of these last. Balanced sanitizer and pH, especially with a salt chlorine generator, protects a cupro-nickel or copper exchanger far better than any coating. Skewed chemistry is what turns a 12-year heater into a 6-year one.
What typically fails. On gas units, the temperature sensor and main board are the most reported failures, appearing in reviews around a year and a half in. On heat pumps, the most common early issues are the app or control panel and first-startup plumbing leaks, followed by compressor or relay problems in cold weather. Expect to replace parts rather than whole units on a long-lived heat pump, and that is a reason to favor a model with a longer warranty.
Where you buy matters. A dealer-installed unit is usually larger and better supported but costs more and has a shorter list of options. A marketplace unit often costs less and arrives by direct delivery, though warranty service still depends on you finding a technician who will work on it. Check the warranty terms against how service is actually provided in your area before you commit.
Heat and Cool Models, Saltwater Pools and Winter Limits
Three questions come up after the heater type is decided, and each one changes which specific unit you should buy. Whether you want one unit to cool as well as heat, whether your pool uses a salt chlorine generator, and how cold your winters actually get all filter the shortlist differently.
Heat and cool versus heat only. Six of the eight units here heat and cool in the same cabinet, and the cooling ranges run from 45F up to 83F depending on the model. That matters more than most buyers expect, because a covered pool in summer can sit high enough that nobody wants to swim. A gas heater does nothing about that at all, so an owner who has both a gas and a heat pump effectively has a cooling solution already. An owner with only gas does not.
The pool volume matters again here, since cooling a large body of water takes far longer than heating it. The units with the highest rated pool ceilings, the 140,000 BTU Varpoolfaye at 42000 gallons and the 120,000 BTU Varpoolfaye at 33000 gallons, are also the ones that can move enough energy to bring a big pool back down in one session.
Saltwater compatibility. Salt water is more aggressive on heat exchangers than chlorine, and the two Varpoolfaye units here are explicitly listed for both freshwater and saltwater. The MICOE and WARMBLU both use a titanium heat exchanger, which resists corrosion better than copper or cupro-nickel. Material choice is only half the answer though, because an exchanger corrodes fast at any material if the sanitizer and pH sit out of range. Salt systems still need active monitoring, and the Hayward in this group includes corrosion protection against unbalanced chemistry for exactly that reason.
Winter limits and the defrost cycle. Every inverter heat pump here lists a minimum operating temperature in the 45F to 47F range for heating, which is the honest number to plan around. Below that threshold the unit runs a defrost cycle to protect itself, and the AQUASTRONG does this automatically every 40 minutes for about five minutes. The practical effect is that on a cold night the heater is pausing repeatedly, which owners describe as a regular interruption rather than a breakdown.
Owners on r/heatpumps are blunt about the limit. A heat pump does very little once the water starts approaching freezing, and the running cost still shows up on the bill. In a climate with hard freezes, the sensible setup is a heat pump for the shoulder season and a gas heater for the cold snaps, which is also why two of the picks here are gas units rather than eight heat pumps.
Where a cover changes the math. Every heat pump performs better under a cover, and the difference is large enough to change a sizing decision. Owners who reported 20 or more degrees in about 24 hours, as the WARMBLU reviews describe, were running a covered pool. Owners on the same units without a cover describe a couple of days for the same result. Decide on the cover first, then size the heater.
Hayward vs Raypak: Which Gas Heater Brand Holds Up Better
Between the two gas heaters analyzed here, the choice is about pool size and how you want to interact with the unit. The Raypak P-R266A-EN-C has more output at 266,000 BTU and owners report roughly 3 degrees per hour, while the Hayward H-Series model here is 150,000 BTU and rated for pools up to 450 square feet.
Speed favors Raypak clearly. Owners of that unit consistently praise heating speed, easy installation when replacing an existing heater, and parts availability for DIY work. The tradeoff is a 210 pound unit, a tight inlet and outlet that needs a bypass loop with extra elbows, and a warranty that requires professional installation.
Controls and installation flexibility favor Hayward. The digital LED panel with self-diagnostics tells you what is wrong instead of making you guess, the low-NOx certification reduces emissions, and connections on either side simplify a tight pad. The tradeoff is capacity, since 150,000 BTU will not carry a large pool or a swim spa.
Reliability data is thin on both. The Raypak has 170 reviews at 4.0 and the Hayward has 160 at 4.2, close enough that the rating difference is not the deciding factor. Pool size and gas line access decide it far more reliably than the stars do.
Frequently Asked Questions
What type of heater is best for a pool?
A gas pool heater is best when you want fast, on-demand heat and already have a gas line. A heat pump pool heater is best when you want to hold a temperature for many hours cheaply. A solar heater is best only as a supplement in a sunny climate. Choose by pool gallons, your coldest nights, and whether a gas line already reaches the equipment pad.
How many BTU heaters do I need for a 16×32 pool?
A 16 by 32 foot pool with an average depth of 5 feet holds about 19200 gallons. Raising it 12 degrees calls for roughly 100,000 to 150,000 BTU of heat pump capacity for a moderate climate, or a 150,000 to 250,000 BTU gas heater if you want the water warm the same day. Larger or deeper pools need more, and colder climates need more.
How do I calculate the size of a pool heat pump I need?
First compute gallons as length times width times average depth in feet times 7.5. Then pick a target temperature rise, usually 12 degrees from 68F to 80F. Then match output BTU to gallons, roughly 100,000 BTU under 10000 gallons, 120,000 BTU in the middle range, and 140,000 BTU above 20000 gallons, adjusting up for colder climates.
How many BTU do I need for a pool heat pump?
Most mid-size inground pools fall between 100,000 and 140,000 BTU of heat pump output. Check the COP as well as the output, since 12.3 to 16.0 is the range on the units here. Also check the rated pool ceiling on the listing, which ranges from 26000 gallons on the MICOE to 42000 gallons on the 140,000 BTU Varpoolfaye.
What’s the 20 rule for heat pumps?
The 20 rule is a sizing shortcut meaning roughly 20,000 BTU of heat pump capacity for a 20000 gallon pool. It is a starting point for a moderate climate, not a fixed rule. Adjust downward for mild areas with good cover use and upward for cold climates, deep pools, or anyone expecting a fast heat-up.
Do pool heat pumps work in cold weather?
They work, but less efficiently. A heat pump pulls heat from outside air, so as ambient temperature falls the available heat and the COP fall with it. Owners report heat pumps taking multiple days in cold weather, and some units freezing up until relays are replaced. A gas heater is the practical backup in climates with hard freezes.
Is a pool heat pump worth it?
For most inground pool owners with steady daily use, yes, because the running cost is far lower than gas or electric resistance. A heat pump rated at about 1300 watts draws roughly what a dehumidifier uses, and a COP of 12 to 16 means each unit of electricity produces 12 to 16 units of heat. The compromise is slower heat-up.
How long does a gas pool heater take to heat a pool?
Owners of the 266,000 BTU Raypak report about 3 degrees per hour with good water flow. On a 19200 gallon pool needing a 12 degree rise, that is roughly 4 hours of continuous burner time. Heat pumps on the same pool are far slower, often 1 to 3 degrees per hour and sometimes several days in cool weather.
Can you use a pool heat pump with a saltwater pool?
Yes, as long as the unit is rated for saltwater. The Varpoolfaye units in this roundup are listed for both freshwater and saltwater pools, and a titanium heat exchanger resists corrosion better than copper. Balanced chemistry matters more in a salt pool, since an unbalanced exchanger corrodes faster whatever material it is made from.
Which pool heater is better, Pentair or Hayward?
Pentair MasterTemp and Hayward units are both well-regarded, and the real difference is model class rather than brand. Hayward models in this review use a digital LED panel with self-diagnostics, low-NOx burners, and hookups on either side. Compare capacity against your pool square footage and confirm local dealer service before choosing between brands.
What is the highest rated pool heater?
Among the eight heaters analyzed here, the Varpoolfaye 140,000 BTU inverter heat pump holds the highest average rating at 4.7 stars, though its 59 reviews are the thinnest in the group. The AQUASTRONG HEX100 has the deepest owner history at 534 reviews and a 4.3 rating, which is stronger evidence of long-term behavior.
Should I buy a bigger BTU heater?
Not automatically. Oversizing a gas burner means paying for unused capacity and running more start-stop cycles, while an undersized heat pump never reaches temperature on a cold week. Size to your actual pool volume and coldest nights, and add a pool cover first, since a cover reduces the work the heater has to do more than any upgrade to the unit.
Conclusion: Which Inground Pool Heater Should You Buy in 2026?
Pick by climate and usage, not by the biggest BTU number on the box. Inverter heat pumps suit mild-to-cool climates and steady daily use, with the AQUASTRONG HEX100 as the strongest all-round choice in this group. Gas suits cold climates, swim spas, and same-day heating, with the Raypak P-R266A-EN-C covering that role.
Measure your gallons, check for a gas line at the pad, and add a pool cover before you upgrade anything. Those three steps tell you more about how the heater will perform than any spec sheet on the box.