5 Best Gas Pool Heaters (2021 Reviews)


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Old-school pool heaters were slow, loud, and inefficient. Whether you’re trying to replace a 20-year old model or you want to get the best bet for your new swimming pool, you need to know what to look for. If you have gas lines run to the equipment pad, you’ll be able to choose from quite a few heaters.

The best gas pool heater is the Pentair Mastertemp 400K BTU Pool Heater. It has an incredible thermal efficiency of 82% thanks to the cupro-nickel heater exchanger. This lightweight pool heater is easy to install, or you could have a professional do it to add a multiyear manufacturer warranty.

Throughout this article, you’ll also learn the following info about the best gas pool heaters on the market:

  • What you need to know before making a purchase
  • Details about the five top gas heaters for any swimming pool
  • How you can use a gas pool heater to get the best bang for your buck

What to Look for When Buying a Gas Pool Heater

It can be tempting to buy the first gas heater that you come across. Every company claims that theirs is the most efficient, long-lasting model available. However, there are three key components that you need to know when you’re negotiating:

  1. BTUs are determined by the size of your swimming pool
  2. Thermal efficiency shows how quickly it will heat up
  3. The initial cost isn’t the end of it

All three of these factors relate to each other, so you can’t base your decision on just one of them. It’s important that you take all three into consideration to know that you’re getting the best heater for your swimming pool. Without further ado, I’ll break down everything you need to know about buying a gas pool heater below.

BTU

BTUs are known as a unit of heat required to heat one pound of water. They’re used with any source of heat. Fortunately, it’s relatively easy to learn how many BTUs your swimming pool will need to increase its temperature. You’ve probably seen many pool companies use 150K BTU or 400K BTU on their heaters. This is the number that you need to look at!

It’s not as simple as calculating your pool gallon total and picking the right heater. You’re more than welcome to follow simple tables (such as the one below) to determine what size heater you’ll need, but there’s something else that you’ll have to read after!

BTUSwimming Pool SizeMax BTU Recommended
50,000 BTU10,000 gallons100,000 BTU
85,000 BTU15,000 gallons125,000 BTU
110,000 BTU20,000 gallons250,000 BTU
125,000 BTU25,000 gallons400,000 BTU
(Source: The Pool Factory)

As you can see, there are multiple suggestions per gallon in total. Some people have 125,000 BTU heaters, while others have an 85,000 BTU heater for the same size pool. Remember that you don’t want to go too far over the limit, or you’ll be wasting your money.

You might be curious about why the recommended BTU is higher than the base level. There are two reasons:

  1. Purchasing a pool heater with higher BTUs will increase the temperature quicker. It’s more powerful, which means you’ll have to wait less time for quick results. A few hundred extra dollars can be the difference of several hours of waiting for it to heat up. It’s up to you to decide if the trade-off is worth it.
  2. If you have additional features, you’ll need more BTUs to heat the whole swimming pool. Connected spas, swim spas, waterfalls, and jets take more time to heat, so you’ll need more power. Again, you’ll have to wait much longer for all of these features to heat if they’re taking a lot of water.

Knowing the BTUs of a swimming pool heater is essential, but it’s not the only necessary measurement. In the next section, you’ll learn how British Thermal Units tie in with thermal efficiency.

Thermal Efficiency

It might seem a bit too technical, but thermal efficiency is a simple process. In layman’s terms, thermal efficiency is the heating rate compared to the amount of power used. For example, if you have a 400K BTU heater, it could heat the pool in 10 hours or 5 hours, depending on the thermal efficiency.

So, what is a good rating? You’d probably assume 100%, right? Unfortunately, no swimming pool heater in the world can achieve such a high percentage. The average pool heater has a thermal efficiency that ranges from 70% to 82%. If you can find anything within that range, you’ll be in luck.

The thermal efficiency is determined by numerous factors, including the heat exchanger’s size, the width of the gas pipes, and more. Cupro-nickel is one of the best materials used in swimming pool heat exchangers. It can increase the water temperature quickly without losing heat out of the unit’s side.

The Copper Development Association states that cupro nickel is a combination of copper and nickel. Both of these materials have an excellent heat exchange rate, which is why so many companies use the combo. Old-school swimming pool heaters used all sorts of materials for their heat exchangers, but it’s safe to say that nothing comes close to modern tech.

Cost (Purchase, Maintenance, and Operation)

Buying a swimming pool is expensive. Many people say it’s like buying a boat; You’re most excited the first day you buy it and the day you sell it. Inefficient heaters can drive up the price tremendously, not including the cost of maintenance. The good news is that all of the heaters on my list are designed to save you money on all phases.

Here’s what you need to consider when you’re thinking about the price of a gas swimming pool heater:

  1. The initial purchase price is going to be the most significant expense. Pool heaters typically range from $1,000 to $4,000 or more. Keep in mind that the BTU, quality, brand, and many other factors will impact the price. Try to set a realistic budget before you get a heater for your pool.
  2. Don’t forget the annual maintenance costs. It’s recommended that you get your pool heater inspected once per year. Many parts that might have to be replaced to repaired include gaskets, gas lines, piping, unions, and more. Numerous internal components need to be cleaned by an expert.
  3. Gas isn’t free! Before you use a pool heater, make sure you know how often you want it to do its job. Here’s some free advice: Keep your heater maintained at a designated temperature setting rather than reheating it every time you want to use it. More gas is used on a one-time heating session than continuous heat leveling.

Now that you know everything that you need to look for when you’re buying a new gas heater for your pool, it’s time to check out our top selections. There are dozens of swimming pool heaters, but most of them cost too much, require maintenance far too often, or they’re not efficient enough to be worth the investment.

With that in mind, here are the five best gas pool heaters of the year:

Our Top Picks

Best Overall: Pentair MasterTemp 400K BTU Pool Heater

Pentair is a leading company in the swimming pool industry. They made heaters, filters, pumps, salt systems, and more. If you want a piece of that quality on your equipment pad, then check out the Pentair Mastertemp 400K BTU Pool Heater. It’s more than powerful enough to heat any pool size up to 45,000 gallons.

It’s designed with rust-resistant materials to prevent long-term damage. There’s so much water running through the pipes that could cause problems down the road. Although moisture isn’t supposed to get into the internal components, it’s nice to know that they’re double-protected to keep your investment safe.

One of the most significant advantages of owning a Pentair heater is that they’re compatible with almost any pool system. They provide unions for 1.5” and 2” piping, allowing you to quickly plumb them into the setup. Furthermore, you can use them with high-tech automation systems to work on their own.

Bottom Line: The Pentair Mastertemp 400K Heater is a top-of-the-line, reliable, long-lasting heater that won’t lose it’s spot at the top any time soon. From the warranty policies to the rust-resistant materials, it’s hard to beat such a high-quality gas-powered swimming pool heater.

Heat ExchangerCupro nickel
BTU400,000 BTU
Thermal Efficiency82%
Weight127 pounds
Dimensions36 x 25 x 30 inches

Pros

  • It has excellent thermal efficiency. At 82%, you’d have a tough time finding a better heater.
  • The extended warranty brings peace of mind. Pentair provides a one-year warranty, but they also offer extended deals for people who get it installed by a professional.
  • It’s built to last a long time. Everything in the Mastertemp is made of high-end, durable materials.
  • It’s one of the most user-friendly heaters. If you’re worried about the installation and operation, you’ll be glad to know that it’s as simple as it gets.
  • A lot of significant pool companies backs Pentair. You can have your Mastertemp heater maintained by almost any swimming pool business in your city.

Cons

  • The Pentair Mastertemp is very expensive. Most people don’t mind, though, because you get what you pay for.
  • The outer shell can be cracked because it’s designed to reduce the weight. Although it’s not the toughest, the internal parts won’t be harmed because they’re made to take a beating.
  • The shell can be stained very quickly. It’s light beige, which means you’ll have a hard time keeping it look new.

Best for Small Pools: Hayward 150K Universal H-Series Heater

Hayward is another well-known brand that countless customers rely on every year. They made various swimming pool products, but the Hayward 150K Universal H-Series Heater is at the top of their designs. It’s an excellent choice if you have a small pool between 10,000 to 20,000 gallons.

If you have a Hayward automation system, you’ll be able to use it with this heater. It can be set to change the temperature during designated times of the day, but you can also put numerous other settings. Without an automation system, you’ll still be able to take advantage of timers and digital temperature settings.

One of the most favorable features of this pool heater is that it’s eco-friendly. You don’t have to worry about loads of emissions ruining the local air quality. It’s incredibly efficient in handling the heat, which means it goes through the system and into the water rather than causing the unit to get too hot.

Bottom Line: Hayward has done it again with the 150K BTU Heater. It’s eco-friendly, compatible with numerous pool systems, and easy to use for everyone. Furthermore, this heater is designed for high water flow, so you don’t have to concern yourself with erosion or corrosion.

Heat ExchangerCupro nickel
BTU150,000 BTU
Thermal Efficiency83%
Weight110 pounds
Dimensions31.3 x 30.8 x 28.6 inches

Pros

  • The thermal efficiency is as good as you’ll find anywhere. As you can see, it’s 1% higher than the impressive 82% of the previous heater.
  • It’s ultra-lightweight in the world of heaters. At 110 pounds, you’ll be able to maneuver this heater with a dolly.
  • The cupro-nickel heat exchanger provides optimal heating. You don’t have to worry about losing the temperature in the process.
  • It comes with a 3-year warranty. Relax knowing that you’re covered for several swimming seasons.
  • Hayward heaters are built to be tough. They won’t break from the rain, snow, hail, or any other weather patterns.

Cons

  • The dimensions are a little bulkier than most small heaters. At 150K BTUs, it should be significantly smaller.
  • You can’t use it with any automation system aside from Hayward’s. Unlike Pentair’s heaters, this one can’t be adapted.
  • The interface feels outdated. It’s not as advanced and responsive as other systems, which might be a deal-breaker.

Best for Easy Installation: Raypak 266K BTU Natural Gas Swimming Pool Heater

Although they’re not as common these days, Raypak heaters were once at the top of the industry. The Raypak 266K BTU NG Swimming Pool Heater is a great option if you plan to DIY the installation. You don’t need much help from a professional if you get this heater because it’s designed with simplicity in mind.

It has two 2-inch unions that are right next to each other for easy positioning. Instead of plumbing through one end and out the other, the Raypak heater is a plug-and-play unit. The gas line inlet it on the right side of the unions. It’s a ¾-inch galvanized union, which is standard across the USA.

Once you’ve installed the heater, you’ll be able to use the LED screen that shows everything from the temperature settings to a timer. Heat your pool and spa whenever you’d like without needing automation. That being said, it’s compatible with many systems, so feel free to grab an adapter.

Bottom Line: The Raypak Heater might not be the most common one in the industry, but many pool owners believe it’s a hidden gem. It sits in the middle of the BTU range, making it worth using for almost any pool size. You can get it installed in under an hour thanks to the detailed manufacturer instructions.

Heat ExchangerCopper (cupro nickel upgrade available)
BTU266,000 BTU
Thermal Efficiency83%
Weight243 pounds
Dimensions38 x 28 x 20 inches

Pros

  • It’s budget-friendly. These heaters are much cheaper than other models of the same BTU range.
  • They’re very efficient. The 83% thermal efficiency rating on this heater is tied for first place.
  • You don’t need any extra parts to install the heater. Aside from the plumber’s glue and pipe dope, everything is provided.
  • The base is very small, which means you don’t have to take up much space on the equipment pad. It also makes the plumbing process easier.
  • The unions are designed to sit at the height of most pumps. When you’re plumbing the heater into the equipment pad, you won’t need too many elbows or couplings.

Cons

  • You have to pay more money if you want a cupro-nickel heat exchanger. Copper is good, but it’s not the best choice.
  • It’s an incredibly heavy heater. Although the installation is easy, it’s a pain to get it in place.
  • There’s not much room under the heater. The underside can get soaked, trapping mildew and heating the equipment pad or ground under it. If it’s on the ground, it’ll slowly sink into the mud.

Best for Pool & Spa Combos: Pentair MasterTemp Pool Heater 250K BTU

You’ve already seen the impressive features of the Pentair 400K, but the Pentair Mastertemp 250K BTU Pool Heater is also worth a look. It’s a bit less powerful than the previous heater by the same brand, but it’s also significantly cheaper. If you want to save money and sacrifice a few extra hours of heating, this is a great choice.

The Pentair Mastertemp is compatible with any modern automation system, much like its predecessor. It also works well with variable speed pumps to save you time and money in the long run. You can set it to turn on at all times or to slowly ramp up the heat during designated times of the day.

The unions are designed for two-inch pipes, but you can use adapters to make it work with 1.5-inch pipes. It uses natural gas, which is the most common fuel for gas-powered heaters these days. Run it through the ¾-inch pipe, and you’ll be good to go.

Bottom Line: Just because it’s a bit slower doesn’t mean the 250K BTU Mastertemp is any less efficient. You’ll receive the same cupro-nickel high-quality heat exchanger for top-notch thermal efficiency. It’s lightweight (for a heater), much more affordable, and you’ll be able to enjoy the product of a thriving company.

Heat ExchangerCupro nickel
BTU250,000 BTU
Thermal Efficiency82%
Weight133 pounds
Dimensions30 x 36 x 23 inches

Pros

  • It’s an excellent choice for people who have a pool and spa. If you have a 15,000-gallon pool attached to a spa, this heater can get it done quickly.
  • The high-end thermal efficiency drives it right below the best available. It’s 1% less than the Hayward and Raypak heaters.
  • It uses rust-proof components to prevent damage. Whether water splashes or raindrops are falling from the sky, your equipment will be safe.
  • This heater is very compact. It has one of the smallest footprints of any gas heater for swimming pools.
  • They’re built with structural integrity. You won’t have to get maintenance or repairs as often as other pool heaters.

Cons

  • It’s a bit heavier than the 400K BTU Mastertemp. The difference is only a few pounds, but you’d think that a less-powerful heater would weigh much less.
  • Much like the previous Pentair Mastertemp, this one has a semi-fragile shell. It’s made of plastic, which seems a bit cheap for such an expensive heater.
  • Pentair replacement parts are costly. On average, you should expect to spend about $15 to $20 more per repair.

Best for Large Pools: Hayward 400,000 BTU Pool Heater

Hayward has quite a few heaters, with the 400K BTU Heater being one of the best in their H-Series lineup. If you want a quick-acting, efficient, powerful heater for your swimming pool, then I highly recommend that you check this one out. It’s a tank of a heater, pulling thousands of gallons of water and heating it in a matter of 10 hours or less.

In the swimming pool industry, most heaters take about 15 hours to make a noticeable difference. The Hayward 400K Heater increases the temperature so fast that the price is no longer an issue for many pool owners. Speaking of which, this model is always significantly cheaper than the Pentair equivalent.

If you’re inclined to maintain the heater without professional help, the front panel makes it easy. Two tabs hold it together. Slide them down and pop off the panel, revealing all of the internal components. Remember to turn off the gas and electricity before you try to repair any swimming pool heater.

Bottom Line: The Hayward H-Series is a tough competitor in the industry. Their 400K BTU heater is one of the best on the market, and in my opinion, it’s the best for large swimming pools. If you have loads of water features and 25,000 gallons or more in your pool, then you’d benefit from this impressive heater.

Heat ExchangerCupro nickel
BTU400,000 BTU
Thermal Efficiency83%
Weight160 pounds
Dimensions37.6 x 30.8 x 28.6 inches 

Pros

  • This heater is excellent for big pools. It can heat a small pool quicker than any other and a big pool at an efficient rate.
  • Speaking of efficiency, the thermal efficiency rating is top-notch. It’s hard to find anything better than 83%.
  • It’s relatively lightweight for a 400K BTU heater. Many others are well over 200 pounds, making this 160-pound model much easier to handle.
  • It uses patented heating technology. If you want instant results, then you’ll love Hayward’s programmable interface that does just that.
  • It’s as eco-friendly as it gets for a swimming pool heater. You won’t be able to find a heater with lower emissions since this one meets all of the zero-emission requirements.

Cons

  • You can only use this heater with Hayward automation systems. Their automation panels aren’t as advanced as Pentair systems, so you could consider an expensive adapter if you want to make the switch.
  • Some people have stated that it’s louder than other heaters. Note that such a powerful heater is expected to make more noise, but it’s something to consider when you’re making the final decision.
  • The membrane interface is a bit cheap. The stickers can feel off easily, though they don’t affect the performance of the heater.

Conclusion

The Pentair Mastertemp 400K Heater is hard to beat on any side. It has enough power for pools and spas, and it’s much lighter than most pool heaters. You can install it by yourself in as little as one hour, which can’t be said for any old-school heater.

However, consider the following scenarios to know if you need a different model:

  • If you have a small pool without extra features, try the Hayward 150K H-Series.
  • For those who want to DIY the installation, get the Raypak 266K NG Heater.
  • I highly recommend the Pentair Mastertemp 250K for pool & spa combos.
  • Large pools require more BTUs, so I suggest the Hayward 400K Pool Heater.

Check out the Pentair Mastertemp 400K BTU Heater on Amazon here!

Jake Alexander

Jake is a freelance writer from Pennsylvania who enjoys writing about science and sports. When he's not writing for Temperature Master, he can be found watching the NFL or playing basketball with his friends.

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