Raypak pool heater review
The gas heater whose listings state a real efficiency figure. What that number is worth, what else is published, and the two things the listing will not tell you.
Quick picks
The Raypak beside the two heaters buyers cross-shop it against. All three are on-demand machines; if you hold a temperature all season, a heat pump beats all of them on running cost.
| # | Product | Best for | Price |
|---|---|---|---|
| 1 |  The one being reviewed Raypak Digital Natural Gas Pool Heater 336,000 BTU/hr input, 82% stated. The gas benchmark on this site for a reason. | Heating fast and occasionally, rather than holding a temperature | |
| 2 |  The alternative up a class Pentair MasterTemp 400 Natural Gas Pool Heater 400,000 BTU/hr and quieter by the listings' account. No efficiency percentage published. | A full-size pool heated on demand, when you want the largest gas class | |
| 3 |  If your gas line says no Hayward Universal H-Series 150,000 BTU Natural Gas Heater 150,000 BTU/hr, under half the demand. Slower, and often the one you can actually install. | A modest pool where the gas supply, not the heater, is the real constraint |
#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 18, 2026.
What is published, and why it matters here
Raypak’s 336,000 BTU digital natural gas heater is the unit we use as the gas benchmark across this site, and the reason is unglamorous: the listings for it state an efficiency figure, 82%, in plain numbers. Most gas-heater listings describe efficiency in adjectives. A stated percentage is something you can do arithmetic with, and arithmetic is what this site is for.
Reading the current listings on 12 September 2026, here is the rest of what is published: a 336,000 BTU/hr input rating; an integral fin copper heat exchanger tube with polymer headers described as corrosion-free; stainless steel burners; a backlit LCD with a microprocessor-controlled, self-diagnostic ignition; temperature and flow control of the exchanger to limit condensation; a non-combustible base so it can sit on a combustible surface; and a convertible 120/240 V electrical supply. It is low-NOx certified and sold in propane as well as natural gas.
That is a fuller list than most of the category offers, and it is the basis of everything below.
What the numbers mean for your pool
| 20,000 x 8.33 x 10°F | = 1,666,000 BTU |
| 336,000 BTU/hr x 82% | = 275,520 BTU/hr delivered |
| 1,666,000 ÷ 275,520 | = about 6 hours |
| Fuel: 1.666 x $28.36 | = $47.24 |
Ideal figures that ignore the heat the pool loses while you heat it, which on a cool night is not small. On propane the same job costs about a quarter more. US average residential prices, EIA, June 2026.
Six hours is the whole product. It is why gas exists: a pool that is eight degrees down at breakfast is swimmable by mid-afternoon, whatever the weather is doing. A heat pump takes about twice as long on the same job and costs about $10.75 per million BTU to do it against $28.36 here. Which of those matters more to you is the decision, and this heater is only the right buy on one side of it.
The exchanger
Copper fin tube with polymer headers. Copper is the conventional gas heater exchanger and it transfers heat well; it is also the component most exposed to water chemistry, and the reason cupro nickel exists as an upgrade on many heaters. Raypak sells a cupro nickel version of this class too, and if you run a salt pool or your chemistry wanders, that is the version to look for. The polymer headers are there precisely to take the corrosion-prone joints out of metal, which is a sensible design choice that no listing quantifies.
The controls
A backlit digital display with a microprocessor ignition that self-diagnoses is, in practice, the difference between reading a fault code and calling someone to guess. The listed exchanger temperature and flow control is aimed at condensation, which is what shortens a gas heater’s life when it runs on short cycles. These are the features that separate the current digital line from the older millivolt designs, and they are the ones worth paying for.
The install, which is where the surprise lives
The non-combustible base and the 120/240 V convertible supply both make the placement easier than older units. The flue does not: this is a combustion appliance and it needs clearance and venting to code, which is not a weekend job for most people.
Natural gas or propane
Raypak sells this class in both. The machine is the same; the fuel is not. Propane costs about $35.66 per million BTU delivered at US average residential prices against about $28.36 for natural gas, and it arrives in a tank on a delivery contract. If you have a line, use it. If you do not, propane is what “gas” means for you and the heat-pump comparison gets harder for it to win.
Who should buy it
- Anyone who heats on demand. A weekend pool, a shoulder-season warm-up for visitors, a cold snap you want to swim through. Speed is the product.
- Anyone in a cold shoulder season where a heat pump fades. Gas does not care what the air is doing.
- Anyone whose gas line can feed it, or can be upsized for less than it would cost to be wrong.
Who should not
- Anyone holding a temperature all season. The running-cost gap to a heat pump compounds daily and this is the wrong machine for that pattern.
- Anyone who has not yet bought a cover. About 70% of a pool’s heat loss is evaporation. A gas heater without a cover re-does the same job every morning, on fuel.
What we could not assess
The efficiency it actually achieves in service, as against the 82% in the listing. The life of the copper exchanger against your water chemistry, which is the number that decides whether it was a good buy in ten years. And whether your gas meter and line can feed it without an upgrade — a question only a gas fitter can answer for your house.
The three-brand comparison puts this unit beside the Hayward and the Pentair on everything each of them publishes.
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.
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 18, 2026.
Pentair MasterTemp 400 Natural Gas Pool Heater
The third name in every gas-heater comparison, and the one the listings describe as the quiet one. It is a 400,000 BTU/hr input heater, low-NOx certified, which puts it in the same class as the biggest Raypak — and therefore in the same speed bracket: hours rather than a day. Pentair does not state a thermal efficiency percentage in the listings we read, so we run it at the 82% we assume for gas generally.
Best for A full-size pool heated on demand, when you want the largest gas class
| Rated input | 400,000 BTU/hrGas convention: fuel burned per hour, not heat delivered. Delivered heat is this figure times the thermal efficiency. | Retail listing |
|---|---|---|
| Emissions | Low NOx certified | Retail listing |
| Thermal efficiency | Not stated as a percentage in the listings we readThe listings say best-in-class efficiency without a number. We run it at 82%, the assumption we use for every gas heater on the site, and would revise it if Pentair published a figure we could cite. | Retail listing |
| Cost per million BTU delivered | About $28.36 at 82% efficiencyUS average residential natural gas at $24.09/Mcf (EIA, June 2026). | Our arithmetic |
- Largest common residential gas class, so the fastest heat-up on this site
- Low NOx certified, so it is permitted in the air districts that require it
- Described across listings as noticeably quieter than the older gas designs
- Roughly two and a half times a heat pump's cost per delivered BTU
- 400,000 BTU/hr demands a gas supply most houses were not piped for
- No thermal efficiency percentage in the listings, so the efficiency claim is unverifiable
- Real delivered efficiency in service
- Heat exchanger life against your water chemistry
- Whether your gas meter and line 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 18, 2026.
Hayward Universal H-Series 150,000 BTU Natural Gas Heater
The gas heater for a pool that does not need 336,000 BTU an hour thrown at it. At 150,000 BTU/hr of input it is under half the fire of a full-size unit, which costs you speed and buys you something people discover too late: a much smaller gas supply to feed. On a modest inground pool or a big above-ground one, that is often the difference between using the gas line you already have and paying to upsize it.
Best for A modest pool where the gas supply, not the heater, is the real constraint
| Rated input | 150,000 BTU/hrHayward publishes this as a BTU/hr rating, in the gas convention: fuel burned per hour, not heat delivered into the water. | Manufacturer |
|---|---|---|
| Current part number | W3HS150FDN, which Hayward's listing states replaces the H150FDNSame heater class, current SKU, with the OmniX control. The older H150FDN part number still appears in older reviews and stock. | Retail listing |
| Heat exchanger | Standard cupro nickelCupro nickel is the corrosion-resistant option on most gas heaters and a paid upgrade on some. Hayward lists it as standard on this one. | Manufacturer |
| Thermal efficiency | Not stated for the current W3HS150FDNConfirmed on Hayward's own product page, read 17 October 2026: there is no thermal efficiency percentage anywhere on it. The only efficiency-shaped figure is a claim of savings of 'up to 18%', which refers to reduced PUMP run time rather than to combustion. An 84% figure circulated in retail copy for the older H150FDN; it does not appear for the current part, so we no longer attach it and run this heater at the 82% we assume for gas generally. | Manufacturer |
| Water flow window | Min 20, max 125Quoted exactly as Hayward publishes it — the specification table does not state the unit, though gallons per minute is the convention and the figures only make sense that way. Hayward advises keeping flow above the minimum with allowance for a dirty filter, to protect the exchanger. | Manufacturer |
| Connections | 2 in x 2-1/2 in CPVC unions | Manufacturer |
| Electrical | 120/240V, 60 Hz single phase, 5.5 circuit amps, 15 A max breakerHayward's table also carries a 'Power: 44 kW' row, which cannot describe this appliance: 5.5 A at 240 V is about 1.3 kW, and 44 kW would not sit behind a 15-amp breaker. We read it as a data-entry artifact and flag it rather than repeat it. | Manufacturer |
| Warranty | 1 year parts, no laborAt the shorter end of this category. For contrast, FibroPool states a Limited Lifetime warranty and TURBRO gives 2 years on the machine with 5 on the compressor, both on much cheaper units. | Manufacturer |
| Cost per million BTU delivered | About $28.36 at our 82% assumptionUS average residential natural gas at $24.09/Mcf (EIA, June 2026) divided by 82%, the same assumption we apply to every gas heater without a published efficiency figure. | Our arithmetic |
- Roughly half the gas demand of a full-size heater, which is often what decides the install
- Cupro nickel heat exchanger listed as standard rather than as an upgrade
- Low NOx certified, so it is permitted in the air districts that require it
- Slow for a gas heater: about 14 hours to lift 20,000 gallons ten degrees
- Still gas, so still roughly two and a half times a heat pump's cost per delivered BTU
- Hayward publishes no thermal efficiency figure for it on its own product page
- The thermal efficiency it actually delivers — no figure is published for the current part
- How the cupro nickel exchanger holds up against your water chemistry
- Whether your gas meter and line 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 18, 2026.
Questions people actually ask
Is the Raypak 336 a good pool heater?
How much does a Raypak 336 cost to run?
What size gas line does a Raypak 336 need?
Raypak 336 or 406?
- 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.
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