Which Raypak Pool Heater Do I Need?
There are four choices to make, and one of them trips up more buyers than the other three combined. Here they are in order.
Decision 1: BTU size
This is the main one, and it's driven by your pool's volume and how fast you want to heat it.
The heaters we stock come in 266,000, 336,000 and 406,000 BTU inputs. All the Raypak Digital units run at 82% thermal efficiency, so multiply the rated input by 0.82 to get the heat actually delivered to your water.
The sizing math is covered fully in our existing guide to what size pool heater you need, and the resulting run times are worked out by pool size in how long it takes to heat an above ground pool. The short version:
| Your situation | Direction |
|---|---|
| Smaller round pool, mild climate, patient | 266,000 BTU |
| Mid-size pool, want reasonable heat-up times | 266,000–336,000 BTU |
| Large round or oval, or cold shoulder seasons | 336,000–406,000 BTU |
| You want to swim in April and October | Size up |
| Windy, exposed site | Size up |
| You'll always use a solar cover | You can size down a step |
The rule most people get backwards: sizing up does not mean spending more on fuel overall. You're buying BTUs, not hours, and a bigger heater delivers the same BTUs in less time. What sizing up actually buys you is speed, plus the ability to reach your target on a cold day when a smaller unit simply can't outrun the pool's heat losses.
The real risk with an undersized heater isn't slowness. It's a heater that never gets there.
Decision 2: Natural gas or propane
This one is straightforward. You buy the version that matches the fuel you have, and these are configured at the factory rather than converted in the field.
Natural gas is usually cheaper per BTU and never runs out. It requires a supply line to the pool equipment with adequate capacity for the distance.
Propane works anywhere. A 266,000 BTU unit burns roughly 2.9 gallons per hour at full fire, so tank size matters, and cold-weather vaporization from a low tank can limit output exactly when you need it.
Before you commit either way, work through the running cost math with your actual local rates. Supply capacity is the most common reason a heater purchase falls through.
Decision 3: Digital or Millivolt ignition
We carry both, and they suit different situations.
Digital (electronic ignition) is the modern standard and what most buyers should choose. There's no standing pilot burning fuel continuously. You get an LCD display, a microprocessor-controlled thermostat, real diagnostics when something goes wrong, and compatibility with two-wire and three-wire pool automation systems. It needs mains power.
Millivolt uses a standing pilot light and a millivolt control system that generates its own operating current. It's simpler, has fewer electronics to fail, and will run without household power, which is why some owners in remote locations or with unreliable power still prefer it. The trade-offs are a pilot that burns continuously, no digital diagnostics, and a pilot that can be blown out in high wind.
Most people should buy Digital. Choose Millivolt if simplicity or power independence genuinely matters more to you than efficiency and diagnostics.
Decision 4: Elevation configuration, the one people miss
This is the decision that causes the most expensive mistakes, and almost nobody warns buyers about it.
Gas heaters are configured for the altitude they'll operate at. Air is thinner at elevation, which changes the air-to-fuel ratio the burner needs. Install a sea-level heater at 5,000 feet and you get incomplete combustion: sooting inside the heat exchanger, nuisance shutdowns, pilot outages, poor efficiency, and a shortened life.
Raypak addresses this by producing the same heater in different factory configurations, orificed and pressure-set for a specific elevation band:
| Configuration | Elevation range |
|---|---|
| Standard | Up to about 2,000 ft |
| #51 | About 2,000–6,000 ft |
| #52 | About 6,000–9,000 ft |
Three things to understand:
This is not a field adjustment. Your installer cannot make a sea-level unit correct for 6,000 feet. You order the right configuration.
The model numbers look nearly identical. Units differ by a stock number rather than an obviously different name, which is exactly why people order wrong. If you're buying anywhere but from us, check the stock number carefully.
Know your actual elevation, not your impression of it. Plenty of places people think of as flat sit above 2,000 feet, including much of the high plains, a lot of the Intermountain West, and pockets elsewhere. Look it up before you order. It takes ten seconds.
If you're above roughly 2,000 feet, call us before you order. We'd rather spend three minutes confirming your elevation than have you install the wrong unit.
What you're getting either way
Some of the reasons we settled on this line, and what they mean practically:
Copper fin-tube heat exchanger. Copper transfers heat efficiently and is the long-standing standard for pool heat exchangers.
Polymer headers. Glass-reinforced polymer resists pool chemistry better than metal headers and reduces the unit's weight, which makes installation easier.
PolyFlo integrated bypass. Balances water flow through the heat exchanger automatically, which prevents condensation and scale buildup. Those are the two things that quietly destroy heater efficiency over time. It also means you don't need to worry about matching a large pump to the heater.
Unitherm governor. Additional condensation protection.
Wind-resistant top design. These heaters are built to keep operating in wind and downdrafts, which matters more than you'd think on an exposed backyard equipment pad.
Ceramic fiber combustion box. Keeps the outer jacket cool and prevents residual heat retention after shutdown, which means the unit can be installed without costly metal heat sinks.
High flow, low pressure drop. These units pass very high flow rates without choking your circulation.
Every unit is plumbed and test-fired before it ships.
A quick decision path
- Work out your pool's gallons
- Decide your target temperature and how fast you want to get there
- Pick a BTU size, and if you're between two, take the larger
- Choose the fuel you actually have
- Choose Digital unless you have a specific reason for Millivolt
- Look up your elevation and choose the matching configuration
- Confirm your gas supply and electrical can support it.
The short version
- 266K, 336K and 406K BTU sizes, all at 82% thermal efficiency.
- Size up if you're between two options, have an exposed site, or want shoulder-season swimming. Sizing up buys speed, not higher fuel cost per BTU.
- Buy the version matching the fuel you have. Propane and natural gas are factory-configured.
- Digital electronic ignition for most people; Millivolt if you need power independence.
- Elevation configuration is not a field adjustment. Standard, #51 and #52 cover different altitude bands. Check yours before ordering.
- Confirm gas supply and electrical before you buy anything.
