Best 400,000 BTU Pool Heaters (2026): 15 Picks
The top pick in this guide is the Hayward H-Series Natural Gas Pool Heater, whose listing states 400,000 BTU, natural gas and an inground pool type, the most details among the leading group. Below it, 14 more pool heaters whose titles state a heating output of 399,000 BTU or more are compared on the details each listing names: fuel type, BTU figure, pool type and model. The ordering rule puts listings with more stated details first, then higher stated BTU, then the order of the catalogue. Prices are live and read at their posting time.
15 picks from 19 pool heaters that match this guide with a price we can quote today, made by 11 makers. Every price below is live and carries the moment it was read.
The picks at a glance
Which one should you buy?
- For an inground pool with a natural gas supply: The Hayward H-Series Natural Gas Pool Heater states 400,000 BTU, natural gas and an inground pool type, so this pick suits an inground pool on a natural gas line. See pick 1
- For an inground pool replacing a propane heater: The Raypak Avia 400K BTU Propane Pool Heater states propane gas and 400,000 BTU while naming inground pools, matching an inground pool that runs on propane. See pick 5
- For a buyer comparing 406,000 BTU listings: Three Raypak listings state a 406,000 BTU output, the highest figure in this list; the Raypak 406k Digital Electronic Ignition Natural Gas Heater leads them on catalogue order. See pick 6
- For a pool at 3,000 to 5,000 feet elevation: The Raypak Digital 406K Propane Gas Pool and Spa Heater names high-altitude operation for 3,000 to 5,000 feet in its title, which a buyer at elevation can weigh against the other propane picks. See pick 9
The 15 picks
1 Stated 400,000 BTU for inground pools
Hayward H-Series Natural Gas Pool Heater for Inground Pools 400
- Heater type
- Natural gas
- Heating output
- 400000 BTU
- Pool type
- Inground
$5,099.00 (as of 10/18/2026 12:02 PDT - Details)
This listing is first because it states three details: a 400,000 BTU output, a natural gas fuel type and an inground pool type, the most details among the leading group. It leads the 3-detail picks by appearing first in the catalogue. The title also names the Universal H Series line.
Pros
- States 400,000 BTU output
- Names natural gas fuel
- Names inground pool type
- First pick by stated detail count
Cons
- Does not state a pool size in gallons
- Does not state a voltage figure
- Does not name wifi, inverter or cooling controls
Good fit if
- An inground pool with a natural gas supply
- A buyer who wants a title that names the pool type
Skip if
- A propane-only pool setup
- A buyer who needs a stated pool size or control details
Verdict: The Hayward H-Series Natural Gas Pool Heater leads this list on the strength of its stated 400,000 BTU output, fuel type and inground pool type.
2 Stated 400,000 BTU propane for inground pools
Hayward H-Series Propane Gas Pool Heater for Inground Pools 400
- Heater type
- Propane gas
- Heating output
- 400000 BTU
- Pool type
- Inground
$5,099.00 (as of 10/18/2026 12:02 PDT - Details)
The propane version of the H-Series sits second because it also states 400,000 BTU, propane fuel and an inground pool type, the same three details as the top pick. It appears later in the catalogue than the natural gas version, so it ranks after it.
Pros
- States 400,000 BTU output
- Names propane gas fuel
- Names inground pool type
- Matches the top pick's stated detail count
Cons
- Does not state a pool size in gallons
- Does not state a voltage figure
- No wifi or inverter controls named
Good fit if
- An inground pool with a propane tank supply
- A buyer who wants the same H-Series line on propane
Skip if
- A pool on a natural gas line
- A buyer who needs a stated pool size or control details
Verdict: The Hayward H-Series Propane Pool Heater matches the top pick's stated detail count on propane gas instead of natural gas.
3 Stated 400,000 BTU natural gas for inground pools
Pentair | SR400NA | Max-E-Therm 400
- Heater type
- Natural gas
- Heating output
- 400000 BTU
- Pool type
- Inground
$4,499.00 (as of 10/18/2026 12:02 PDT - Details)
The Max-E-Therm states 400,000 BTU, natural gas and an inground pool type, three details that put it in the leading group. It sits third because it appears after the two Hayward listings in the catalogue. The title also names low NOx operation.
Pros
- States 400,000 BTU output
- Names natural gas fuel
- Names inground pool type
- Title names low NOx
Cons
- Does not state a pool size in gallons
- Does not state a voltage figure
- No wifi or inverter controls named
Good fit if
- An inground pool with a natural gas supply
- A buyer who wants a title that names low NOx
Skip if
- A propane-only pool setup
- A buyer who needs a stated pool size or control details
Verdict: The Pentair Max-E-Therm ranks third on the same three stated details as the leading Hayward listings.
4 Stated 400,000 BTU with NiTek heat exchanger
Raypak Avia 400K BTU Natural Gas Pool Heater for Inground Pools Gas Pool
- Heater type
- Natural gas
- Heating output
- 400000 BTU
- Pool type
- Inground
$4,780.00 (as of 10/18/2026 12:02 PDT - Details)
The Avia natural gas listing states 400,000 BTU, a natural gas fuel type and an inground pool type, joining the leading 3-detail group. It appears after the Pentair Max-E-Therm in the catalogue, so it ranks fourth. The title also names a NiTek heat exchanger.
Pros
- States 400,000 BTU output
- Names natural gas fuel
- Names inground pool type
- Title names a NiTek heat exchanger
Cons
- Does not state a pool size in gallons
- Does not state a voltage figure
- No wifi or inverter controls named
Good fit if
- An inground pool with a natural gas supply
- A buyer who wants a title that names a heat exchanger material
Skip if
- A propane-only pool setup
- A buyer who needs a stated pool size or control details
Verdict: The Raypak Avia Natural Gas Heater takes fourth place with the same stated detail count as the leading group.
5 Stated 400,000 BTU propane for inground pools
Raypak Avia 400K BTU Propane Pool Heater for Inground Pools Pool and Spa
- Heater type
- Propane gas
- Heating output
- 400000 BTU
- Pool type
- Inground
$4,200.00 (as of 10/18/2026 12:02 PDT - Details)
The Avia propane listing states 400,000 BTU, propane fuel and an inground pool type, and appears directly after its natural gas twin in the catalogue, closing the 3-detail group at fifth place. The title names a copper heat exchanger.
Pros
- States 400,000 BTU output
- Names propane gas fuel
- Names inground pool type
- Title names a copper heat exchanger
Cons
- Does not state a pool size in gallons
- Does not state a voltage figure
- No wifi or inverter controls named
Good fit if
- An inground pool with a propane tank supply
- A buyer who wants a title that names a copper heat exchanger
Skip if
- A pool on a natural gas line
- A buyer who needs a stated pool size or control details
Verdict: The Raypak Avia Propane Heater closes the leading group with the same three stated details as its natural gas twin.
6 Stated 406,000 BTU natural gas
Raypak 406,000 BTU Digital Electronic Ignition Natural Gas Pool Heater
- Heater type
- Natural gas
- Heating output
- 406000 BTU
$4,200.00 (as of 10/18/2026 12:03 PDT - Details)
This is the first of the 2-detail picks: it states a 406,000 BTU output and natural gas fuel, but no pool type. Its BTU figure is the highest stated in this list, so it leads the 2-detail group. The title also names digital electronic ignition.
Pros
- States the highest BTU in this list at 406,000
- Names natural gas fuel
- Title names digital electronic ignition
Cons
- Does not name a pool type
- Does not state a pool size in gallons
- No voltage or wifi details stated
Good fit if
- A buyer who wants the highest stated BTU in this list
- A pool on a natural gas supply where the pool type is not named
Skip if
- An inground pool owner who wants the pool type stated
- A buyer who needs a stated pool size or control details
Verdict: The Raypak 406,000 BTU Digital Electronic Ignition Natural Gas Heater leads the 2-detail group on its stated 406,000 BTU output.
7 Stated 406,000 BTU with cupro nickel
Raypak 406,000 Btu Digital Natural Gas Pool Heater
- Heater type
- Natural gas
- Heating output
- 406000 BTU
$4,540.00 (as of 10/18/2026 12:03 PDT - Details)
The second 406,000 BTU natural gas listing states the same output and fuel but differs by naming a cupro nickel heat exchanger in the title. It ranks after the first 406k natural gas listing by catalogue order.
Pros
- States 406,000 BTU output
- Names natural gas fuel
- Title names a cupro nickel heat exchanger
Cons
- Does not name a pool type
- Does not state a pool size in gallons
- No voltage or wifi details stated
Good fit if
- A buyer who wants a title that names a cupro nickel heat exchanger
- A pool on a natural gas supply
Skip if
- An inground pool owner who wants the pool type stated
- A buyer who needs a stated pool size or control details
Verdict: The Raypak 406,000 BTU Digital Natural Gas Heater with Cupro Nickel ranks seventh on its stated output and heat exchanger detail.
8 Stated 406,000 BTU propane
Raypak 406,000 BTU Digital Electronic Ignition Propane Pool Heater
- Heater type
- Propane gas
- Heating output
- 406000 BTU
$4,200.00 (as of 10/18/2026 12:03 PDT - Details)
The propane version of the 406k electronic ignition listing states a 406,000 BTU output and propane fuel. It follows the two natural gas 406k listings by catalogue order, giving the 2-detail group three 406k units.
Pros
- States 406,000 BTU output
- Names propane gas fuel
- Title names digital electronic ignition
Cons
- Does not name a pool type
- Does not state a pool size in gallons
- No voltage or wifi details stated
Good fit if
- A buyer who wants the highest stated BTU on propane in this list
- A pool with a propane tank supply
Skip if
- An inground pool owner who wants the pool type stated
- A buyer who needs a stated pool size or control details
Verdict: The Raypak 406,000 BTU Digital Electronic Ignition Propane Heater ranks eighth, the first propane pick with a 406,000 BTU figure.
9 Names high altitude for 3,000 to 5,000 feet
Raypak Digital 406K BTU Propane Gas Pool & Spa Heater
- Heater type
- Propane gas
- Heating output
- 406000 BTU
$4,200.00 (as of 10/18/2026 12:02 PDT - Details)
This listing also states a 406,000 BTU output and propane fuel, and uniquely names high-altitude operation for 3,000 to 5,000 feet elevation. It appears after the other 406k propane listing in the catalogue, so it ranks ninth within the 2-detail group.
Pros
- States 406,000 BTU output
- Names propane gas fuel
- Title names high-altitude operation for 3,000 to 5,000 feet
Cons
- Does not name a pool type
- Does not state a pool size in gallons
- No voltage or wifi details stated
Good fit if
- A pool at 3,000 to 5,000 feet elevation with a propane supply
- A buyer who wants a title that names altitude operation
Skip if
- A pool below 3,000 feet elevation
- An inground pool owner who wants the pool type stated
Verdict: The Raypak Digital 406K Propane Gas and Spa Heater ranks ninth, distinguished by its stated high-altitude range.
10 Stated 400,000 BTU propane
Pentair 460737 MasterTemp High Performance Eco-Friendly Pool Heater
- Heater type
- Propane gas
- Heating output
- 400000 BTU
$4,281.00 (as of 10/18/2026 12:02 PDT - Details)
With a 400,000 BTU output and propane gas fuel, this Pentair listing falls between the 406k and 399k picks in the 2-detail group by stated BTU. It sits at tenth place because its BTU is lower than the 406k units and higher than the 399k units.
Pros
- States 400,000 BTU output
- Names propane gas fuel
- Pentair brand in the title
Cons
- Does not name a pool type
- Does not state a pool size in gallons
- No voltage or wifi details stated
Good fit if
- A pool with a propane tank supply
- A buyer who wants a stated 400,000 BTU output on propane
Skip if
- An inground pool owner who wants the pool type stated
- A buyer who needs a stated pool size or control details
Verdict: The Pentair MasterTemp Propane Heater ranks tenth, between the 406k and 399k BTU groups.
11 Stated 399,000 BTU with ASME in the title
Raypak Digital Cast Iron ASME Natural Gas 399
- Heater type
- Natural gas
- Heating output
- 399000 BTU
$5,002.00 (as of 10/18/2026 12:02 PDT - Details)
This listing states a 399,000 BTU output and natural gas fuel, the lowest BTU group in the list. It leads the 399k picks by appearing first among them in the catalogue, and the title names cast iron and ASME construction.
Pros
- States 399,000 BTU output
- Names natural gas fuel
- Title names cast iron and ASME
Cons
- Does not name a pool type
- Does not state a pool size in gallons
- No voltage or wifi details stated
Good fit if
- A buyer who wants a stated 399,000 BTU natural gas output
- A buyer who wants ASME named in the title
Skip if
- An inground pool owner who wants the pool type stated
- A buyer who wants a 400,000 BTU or higher figure
Verdict: The Raypak Digital Cast Iron ASME Natural Gas Heater leads the 399k group at eleventh place.
12 Stated 399,000 BTU with bronze headers
Raypak 399k BTU Digital Natural Gas Pool Heater ASME I Bronze Headers I
- Heater type
- Natural gas
- Heating output
- 399000 BTU
$5,596.00 (as of 10/18/2026 12:02 PDT - Details)
Another 399,000 BTU natural gas listing, this one names bronze headers and a cupronickel heat exchanger in the title. It appears after the cast iron ASME listing in the catalogue, so it ranks twelfth.
Pros
- States 399,000 BTU output
- Names natural gas fuel
- Title names bronze headers and cupronickel heat exchanger
Cons
- Does not name a pool type
- Does not state a pool size in gallons
- No voltage or wifi details stated
Good fit if
- A buyer who wants a title that names bronze headers
- A pool on a natural gas supply
Skip if
- An inground pool owner who wants the pool type stated
- A buyer who wants a 400,000 BTU or higher figure
Verdict: The Raypak 399k Digital Natural Gas Heater ranks twelfth on its stated 399,000 BTU and header detail.
13 Names low NOx and 399,000 BTU
Raypak 399K BTU Low NOx Digital IID Natural Gas Pool Heater ASME I
- Heater type
- Natural gas
- Heating output
- 399000 BTU
$5,400.00 (as of 10/18/2026 12:02 PDT - Details)
This 399,000 BTU natural gas listing names low NOx and a digital IID control in the title. It appears after the previous 399k pick in the catalogue, ranking thirteenth.
Pros
- States 399,000 BTU output
- Names natural gas fuel
- Title names low NOx and digital IID
Cons
- Does not name a pool type
- Does not state a pool size in gallons
- No voltage or wifi details stated
Good fit if
- A buyer who wants low NOx named in the title
- A pool on a natural gas supply
Skip if
- An inground pool owner who wants the pool type stated
- A buyer who wants a 400,000 BTU or higher figure
Verdict: The Raypak 399K Low NOx Digital IID Heater ranks thirteenth, with low NOx named in its title.
14 Stated 399,000 BTU propane, named commercial
Raypak B-R406A-EP-X #57 Digital 399k BTU ASME Propane Gas Commercial
- Heater type
- Propane gas
- Heating output
- 399000 BTU
$5,592.98 (as of 10/18/2026 12:02 PDT - Details)
This is the propane entry in the 399k group, stating 399,000 BTU and propane fuel and naming commercial use in the title. It appears last among the 399k picks by catalogue order, ranking fourteenth.
Pros
- States 399,000 BTU output
- Names propane gas fuel
- Title names commercial swimming pool heater
Cons
- Does not name a pool type
- Does not state a pool size in gallons
- No voltage or wifi details stated
Good fit if
- A commercial pool with a propane supply
- A buyer who wants a 399,000 BTU propane figure
Skip if
- An inground pool owner who wants the pool type stated
- A residential buyer who wants a residential label
Verdict: The Raypak B-R406A-EP-X Propane Heater ranks fourteenth as the only commercial-labeled pick in this list.
15 States only a 400,000 BTU output
Pentair Mastertemp 400K Btu Heater 460805
- Heating output
- 400000 BTU
$4,739.00 (as of 10/18/2026 12:02 PDT - Details)
This Pentair listing states a 400,000 BTU output and nothing else in the title: no fuel type and no pool type. With 1 stated detail it sits at the bottom of the ordering rule, but it is the only pick whose title is limited to an output figure.
Pros
- States 400,000 BTU output
- Pentair brand in the title
- 1 stated detail, the minimum for this list
Cons
- Does not name a fuel type
- Does not name a pool type
- No pool size, voltage or control details stated
Good fit if
- A buyer who only has a stated BTU figure to compare
- A buyer who wants a bare-output listing
Skip if
- A buyer who needs a fuel type stated
- An inground or above ground owner who wants the pool type stated
Verdict: The Pentair Mastertemp 400K ranks fifteenth, distinguished by stating only a 400,000 BTU output.
Side by side
| # | Pool heater | Heater type | Heating output | Pool type | Pool size | Voltage | Inverter heat pump |
|---|---|---|---|---|---|---|---|
| 1 | Hayward H-Series Natural Gas Pool Heater for Inground Pools 400 | Natural gas | 400000 BTU | Inground | not stated | not stated | not stated |
| 2 | Hayward H-Series Propane Gas Pool Heater for Inground Pools 400 | Propane gas | 400000 BTU | Inground | not stated | not stated | not stated |
| 3 | Pentair | SR400NA | Max-E-Therm 400 | Natural gas | 400000 BTU | Inground | not stated | not stated | not stated |
| 4 | Raypak Avia 400K BTU Natural Gas Pool Heater for Inground Pools Gas Pool | Natural gas | 400000 BTU | Inground | not stated | not stated | not stated |
| 5 | Raypak Avia 400K BTU Propane Pool Heater for Inground Pools Pool and Spa | Propane gas | 400000 BTU | Inground | not stated | not stated | not stated |
| 6 | Raypak 406,000 BTU Digital Electronic Ignition Natural Gas Pool Heater | Natural gas | 406000 BTU | not stated | not stated | not stated | not stated |
| 7 | Raypak 406,000 Btu Digital Natural Gas Pool Heater | Natural gas | 406000 BTU | not stated | not stated | not stated | not stated |
| 8 | Raypak 406,000 BTU Digital Electronic Ignition Propane Pool Heater | Propane gas | 406000 BTU | not stated | not stated | not stated | not stated |
| 9 | Raypak Digital 406K BTU Propane Gas Pool & Spa Heater | Propane gas | 406000 BTU | not stated | not stated | not stated | not stated |
| 10 | Pentair 460737 MasterTemp High Performance Eco-Friendly Pool Heater | Propane gas | 400000 BTU | not stated | not stated | not stated | not stated |
| 11 | Raypak Digital Cast Iron ASME Natural Gas 399 | Natural gas | 399000 BTU | not stated | not stated | not stated | not stated |
| 12 | Raypak 399k BTU Digital Natural Gas Pool Heater ASME I Bronze Headers I | Natural gas | 399000 BTU | not stated | not stated | not stated | not stated |
| 13 | Raypak 399K BTU Low NOx Digital IID Natural Gas Pool Heater ASME I | Natural gas | 399000 BTU | not stated | not stated | not stated | not stated |
| 14 | Raypak B-R406A-EP-X #57 Digital 399k BTU ASME Propane Gas Commercial | Propane gas | 399000 BTU | not stated | not stated | not stated | not stated |
| 15 | Pentair Mastertemp 400K Btu Heater 460805 | not stated | 400000 BTU | not stated | not stated | not stated | not stated |
How we picked
This guide draws from a catalogue of 17 pool heaters whose listing titles state a heating output of 399,000 BTU or more, including natural gas and propane units. The list ranks picks by the number of details each title states (type, BTU, pool type, fuel), then by stated BTU from highest to lowest, then by the order the listings appear in the catalogue. No pool size is matched to a BTU figure, and no operating cost or heating time is computed, because the catalogue carries no data for them. The pool is dominated by Raypak listings, so the list keeps a spread where the pool allows it and includes 10 Raypak models that differ on BTU figure, fuel and stated pool type, together with 2 Hayward and 3 Pentair heaters. Picks are compared only on the details stated in their listing titles and on live prices.
How to choose
What a 400,000 BTU figure states and what it leaves out
Every listing in this guide states a heating output of 399,000 BTU or more in its title. The figure names the output the unit is sized for, but it does not tell a buyer which pool size it suits, how fast the water warms, or what the operating cost is. The catalogue has no data for those. The maker's sizing page and manual, and a licensed installer, are where a pool size match should be made.
Natural gas or propane: what the titles name
Each pick states either natural gas or propane as its fuel. A natural gas heater is fed by a gas supply line; a propane heater draws from a propane tank. The listing title names the fuel type, and some titles also name the pool type the unit is made for, such as inground. No heat pump or solar heater appears in this list, because every title states a gas fuel.
Inground and above ground: what the titles name
Some titles name an inground pool type, while others leave the pool type out entirely. When a title does not state a pool type, this guide writes 'not stated by the seller' rather than guessing. A buyer with an above ground pool should read the maker's product page and manual before choosing, because the catalogue has no above ground data for these heaters.
Who installs and wires pool equipment
A licensed gas installer and the maker's manual decide installation, and any electrical work is done by a licensed electrician as the maker's manual says. This guide never gives wiring, gas pipe, venting or clearance steps.
What to check before you buy: local requirements and utility
Before buying a gas pool heater, check with the local building office and the gas utility for local requirements. This guide does not summarize any rule or program, because those vary by location and are not in the catalogue.
What this guide leaves out (and why)
This guide compares heater listings on the details each title states: fuel type, BTU figure, pool type and model. It does not compute operating cost, heating time, efficiency, noise, durability or pool size coverage, and it never promises an outcome. The catalogue has no data for those measures.
Questions
Does a 400,000 BTU heater suit your pool size?
This guide does not match a 400,000 BTU figure to a pool size. The listings state only their BTU output, and the catalogue has no pool size or heating time data. The maker's sizing page and manual, along with a licensed installer, are where a pool size match should be made.
What fuel types do these listings state?
Every pick here states either natural gas or propane as its fuel. A natural gas heater is fed by a gas supply line, and a propane heater draws from a propane tank. The title names the fuel type; when a title leaves out a pool type, this guide writes 'not stated by the seller'.
Does this guide cover operating cost, rebates or energy savings?
No. The catalogue carries no operating cost, heating time, efficiency or rebate data, and this guide never computes a saving or a payback. For local rules, check with the local building office and the gas utility. The Pentair, Raypak and Hayward pages linked in the sources describe product lines without cost figures.
Who installs a 400,000 BTU gas pool heater?
A licensed gas installer and the maker's manual decide installation, including gas supply and venting. This guide never gives gas pipe, venting, clearance or fuel conversion instructions. Any electrical work is done by a licensed electrician as the maker's manual says.
Why does this list include heaters below 400,000 BTU?
The catalogue window is 399,000 BTU and up, so listings that state 399,000 BTU appear alongside the 400,000 BTU units. The ordering rule puts higher stated BTU first within each detail group, which is why the 399k picks sit at the bottom of the list.
Recent updates
- : First published.