Pool Equipment 

Best Pool Heater Of 2021 Inground & Above Ground

Get Advice and Reviews From all Types of Swimming Pool Heaters Including Inground, Above Ground  Solar, Gas, Propane, Heat Pump and Much More!

By Allen Hayward

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The Best Propane Heater


The Best Natural Gas Heater


The Best Pool Heat Pump


The reason to purchase a pool heater should be obvious. When it gets cold outside, you may want to still go swimming in your pool. So, you need a heater to warm up the water and make it comfortable to be in there.

If you’re like most newbies, you probably don’t know where to start when it comes to purchasing a heater. After all, not all heaters are the same. In fact, there are three different types of pool warmers which will be discussed in this guide. These include pool heat pumps, solar heaters, and gas heaters. Below we’ll discuss how each type functions, their cost, choosing the appropriate size, advantages, disadvantages, and the cost savings of using a heater and cover on your pool.

It is worth mentioning that “British thermal units” are used to measure the size of a heater. In other words, when a heater generates a certain amount of heat, the measurement of this heat is a BTU. The general heat output range is between 75,000 and 450,000 BTUs.

Top Swimming Pool Heaters

Below is a list of the top pool warmers available on the market. There are various features which make each one uniquely great. Some are more affordable while others are of better quality. We’ve provided you with enough information about these heaters to help you make the top choice.


Best Pool Heater

1. Hayward W3H400FDN Universal H-Series 


Editor’s Choice


How We Review

Hayward H400FDN Universal H-Series Pool Heater Gas 400K BTU

Why we chose it

The Hayward H400FDN is the perfect Inground pool warmer for a big pool. It’s heating power goes up to 400,000 BTUs, which should be more than enough to heat any standard residential sized pool. The H400FDN design is like other Hayward product designs. This allows you to easily replace an older Hayward product that you may have already. Compatibility won’t be an issue.

The H400FDN produces few emissions and runs quite efficiently. Even though you’ll see an increase in your heating bill, it won’t be as much as it would be with other types of heating systems. Its digital panels can easily be used to quickly adjust settings, including the temperature settings of the pool water.


Runner Up Natural Gas Pool Heater

2. Raypak Natural Gas Pool and Spa Heater


Editor’s Choice


How We Review

Raypak Natural Gas Pool and Spa Heater

Why we chose it

This is great for heating most in-ground swimming pools. It starts up quickly without a pilot light, so the water warms quickly even when the temperature outside is cold. The digital display and indicator lights are easy to read. For this reason, you shouldn’t have trouble setting the most ideal water temperature for yourself.

Overall, it is an affordable Inground pool warmer which is durable and works fast to heat the water. If you can tolerate the small amount of noise it makes, then you shouldn’t mind this heater.


Best Above Ground Pool Heater

VINGLI Solar Pool Heater Above Ground Domed


Editor’s Choice


How We Review

The Best Pool Heat Pump

Hayward W3HP21404T Pool Heat Pump


Editor’s Choice


How We Review

The Hayward HeatPro W3HP21004T Pool Heat Pump

The Hayward HeatPro W3HP21004T is the top heat pump overall. It is a powerful pump with heat exchangers that make it corrosion-resistant and rust-resistant. You can expect the temperature of your pool to be 15 degrees warmer within 24 to 48 hours. It uses a whopping 140,000 BTU of power to make that happen.

Do not worry about noise because this pool heat pump is quiet while it is activated. Its noise resistant qualities can be attributed to its scroll compressor and acoustic compressor cover. If you like to plan large events in your backyard, you certainly won’t want to hear any noise coming from your pool heat pump. Now you can enjoy the silence you’ve always wanted with the quiet operation of the Hayward HeatPro W3HP21004T.


The Best Solar Pool Heater

SmartPool S601P SunHeater Solar Heating System


Editor’s Choice


How We Review

TSmartPool S601P SunHeater Solar Heating System

The SmartPool S601P SunHeater Heating System is an economical choice for a pool warmer. Rather than rely on electricity to heat the water, this heating system utilizes the sun’s UV energy to generate heat for the water. Whenever it is a sunny day outside, you’ll have the warmest pool in your neighborhood, and it won’t cost you anything extra on your power bill each month. 

This solar heating system consists of 80-square foot panels, collector tubes, and a pump. You can expect your  water temperature to be raised by a couple of degrees minimum on a sunny day. If you have direct sun exposure to your pool, the water could even get warmer than that. The SmartPool S601P is compatible with above ground and in-ground swimming pools. 

Hopefully, you’re good at figuring instructions out on your own because you won’t get much of a manual guide with this heating system. But you can always look up tutorials on the internet if you get confused. One thing to remember is to be careful of the water pressure. If the pump is on full blast, the water pressure can disconnect the solar panels.

Advantages of a Pool Heater

Each type of heater has its own unique advantages, whether it’s a heat pump, electric heater, or gas heater. Let’s look at some benefits that are common.

Longer Swimming Season

It is expensive to purchase and maintain a pool. The lifespan of a pool ranges from 3 to 15 years. And you won’t even be using the pool the entire year either. Due to the weather, only a few months per year will be suitable for swimming. As a result, you probably won’t get a lot out of a pool.

However, a Inground heater can prolong the swimming season into the colder months because it heats up the temperature of the water. This may not be the case for the winter season, but it can sure make the water comfortable in the fall and spring. But if you only have a mild winter season where you live, then perhaps the heater can make the water comfortable all year long. If this is the case, then a heater and pool are definitely great investments.

Swim at Night

If you live in a tropical region where it is warm, then it might already be okay to swim at night. But if you live in a location where the water temperature decreases after the sun goes down, then you’ll need a  heater to swim comfortably at night. This is helpful if you’re throwing a party or some other kind of gathering at night. Perhaps you want to swim early in the morning and get your workout over with before you start your day.

Beneficial to Your Health

If you swim in warm water, it is better for your overall health. It is also a great form of cardiovascular exercise, especially if you’re suffering from joint pains. On the other hand, if you swim in cold water, then it can cause negative symptoms for people with weak immune systems or arthritis sufferers.

A pool heater will warm up the water and make it more relaxing for your muscles and joints.

Types of Pool Heaters for Inground Pools and Above Ground Pools

1) Solar Pool Heaters

Solar heaters may be the most expensive to purchase, but they’ll save you the most money in the long term. These heaters pump the  water to the pool filter. While this is going on, some of the water goes through a series of “solar collectors” which causes it to warm up. Then it reenters the pool and circulates with the rest of the water.

There are two types of solar pool heaters available.

The unglazed collectors are heaters which use heavy-duty panels made of plastic or rubber and a UV light inhibitor.

The glazed collectors are heaters which use an aluminum plate with copper tubing and an iron-tempered glass cover.

You get more durability with glazed collectors, which is why they’re more expensive. But you do get freeze protection with both unglazed and glazed collectors. That way, cold weather won’t affect the heater.

The Cost of a Solar Heater

The total cost of a solar heating system is typically around $3,000 to $4,000. This price includes the installation cost too.

Choosing the top Solar Heater Size

You need plenty of backyard space for a pool heater. The solar collector you choose should have a surface area that is equal to 75% or 100% of the pool area, depending on the environment. For instance, if you live in a southern state in America and you have an inground pool with the dimensions of 16’ x 32’, then the surface area of your solar collector needs to equal 100% of that square footage. In this case, it would be 512 square feet. But if you live in a northern state, then your solar collector’s surface only needs to equal 75% of the square footage of the pool. That would make it 384 square feet in this example.

The  pump needs to be the appropriate size to accommodate the heating system. If you have an existing  heater that you’re replacing, then you may need a bigger or stronger pump to allow the water to push through this new system.


Do your homework before purchasing a heater and hiring an installer. First, you must inspect your backyard and take measurements to see if the heater will even fit there. If you have a big pool, you need more square footage for the collector. If the collector and pool end up being far away from each other, you will need a bigger pump with additional horsepower.

Consider your surrounding environment too. Just do your own research and measurements before contacting a professional installer. If you need further assistance in determining whether your property is suitable for a solar heater, search on the internet, and you’ll find some helpful articles.

2) Gas Pool Heaters

Propane or natural gas is used as the fuel for a heater. As water enters the heater through a hot tube, the combustion chamber heats up the water. The water comes back out and goes into the pool.

Liquid Propane vs. Natural Gas

The price and availability of different types of fuel in your area will determine which one you use. Fortunately, a liquid propane heater and natural gas heater cost the same amount.

If you use natural gas to heat your home, you can use it to heat your pool as well. Otherwise, you can purchase and install one of those big propane tanks in your backyard. Just be prepared to have it refilled on a regular basis. You’ll be paying about 2.5 times more money for propane than you would for natural gas. It all depends on how much supply there is versus the demand for it.

Electric Ignition vs. Millivolt

Millivolt refers to having a tiny amount of gas to sustain the flame of a pilot light. That way, it can fire up whenever you need it to. An electric ignition generates a spark to light the burners, like what is done with a gas grill. To avoid the chances of a leak, it is better to use the electric ignition.

Gas Heaters: Normal vs. Low NOx Emissions

If your gas heater is “Low NOx,” then it doesn’t release too many emissions. In addition, Low NOx heaters heat the water faster and have more efficiency than your standard heaters.

Most importantly, Low NOx heaters satisfy the NOx Emissions standards that were established by the Texas Natural Resource Conservation Commission Code and the California South Coast Quality Air Management Commission. Therefore, anyone living in Texas or California must use a Low NOx gas heater for their pool.

Additional Features

Single Thermostat vs. Dual Thermostat – Dual thermostats come with most heaters. You can use them to monitor the temperature of both the spa and pool. If you purchase a small heater, there is just one thermostat.

Wind Resistance – Try to find a heater that is designed to be wind resistant or has a forced draft system. Then you don’t need to worry about outside weather elements compromising the heat in your pool.

Average Cost of a Heater

The average cost of a natural heater is anywhere from $300 to $600 monthly. The monthly cost of a propane heater is even more.

The newest heaters for inground pools can cost anywhere from $1,500 to $3,500. It all depends on the brand, size, and type of heater.

Choosing the Correct Size

What is the square footage of your pool’s surface area? You must figure this out before choosing a  heater. Also, research the average temperature of the air in your location. Do this for the coldest month of the year. Now figure out what you want the temperature of your water to be.

The average temperature of your location for the coldest month gets subtracted from the desired temperature you want for the water. Once you do this calculation, you will know how much the temperature must rise. To find the square footage of the surface area of your pool, multiply the length and width of this area.

After you’ve made all these calculations, there is a formula that you can use to determine how many BTUs must come out of your heater.

The formula is Square Footage of Pool Area * Temperature rise * 12.

Let’s say you live in New Jersey and you own an in-ground pool that is 16’ x 32’. If you don’t know what the average temperature is in your location, just visit the U.S. Climate Data website and you can find this information. In New Jersey, the average temperature in October is 65°F.

If you wanted your pool water to always be 80°F, then you would calculate your temperature rise with this equation:

80°F – 65°F = 15°F in Temperature Rise

Going back to the BTU formula, this would be the equation:

512 square feet of surface area * 15 in temperature rise * 12 = the heater must produce 92,160 BTUs of heat for the water.

BTU output determines the rating of a pump  heater. The same applies to a gas heater too. But what makes pumps different is their amount of horsepower is also rated. The average size of a heat pump is 3.5 horsepower/75,000 BTUs, 5 horsepower/100,000 BTUs, and 6 horsepower/125,000 BTUs.

Don’t purchase a heater until you know how far away it will be installed from the meter. You may have correctly sized the heater, but that doesn’t mean the size of the line will be compatible with it. If you were to purchase a $2,000 heater under these circumstances, connecting a new line may cost you anywhere from $500 to $1,000. This means you’ll have more expense to deal with.

What to remember:

  • Figure out the distance between the gas meter and heater
  • Figure out the size of the gas line
  • Determine whether power is available in the location where the heater is going.
  • If you know all this information before purchasing a  heater, it will save you so much trouble and money.

3) Heat Pumps

Gas heaters can heat your pool water quickly. However, someone who is environmentally friendly won’t like the idea of using them. But you can always reduce the amount of gas used by trapping the heat in the water with a solar cover.

Water goes into your heat pump and passes through it. A fan inside of the pump blows outside air toward an evaporator coil which has liquid refrigerant in it. This is how heat is generated. The heat then gets absorbed by the refrigerant and converts into warm gas. Once the gas reaches the compressor, the heat increases and ends up reaching the condenser. The hot gas is added to the water by the condenser. Then the hot gas goes back into the condenser and passes through it. This is where it turns into a liquid again and then goes to the evaporator coil again. The process repeats itself.

The Cost

The initial cost of a  pump is higher than the cost of a gas heater. However, heat pumps are less costly to run and maintain throughout the season. They also don’t go bad as fast as gas  heaters do.

The starting price range of a  pump is between $2,000 and $3,000. The more expensive ones are around $4,000 to $5,000.

The cost of operating the pump depends on your location. Warmer areas won’t be as costly to run a pump compared to colder areas. For instance, if you live in Florida and own an outdoor pool, it costs $1,400 each year to keep the temperature of the water at 80°F. But if you place a cover on the pool, it only costs you $300.

For those who live in the northern states of America, it costs roughly $1,100 yearly to keep your outdoor water temperature at 80°F between the months of May and August. If you have a cover, it only costs $120.

Choosing the Top Heat Pump Size

BTU output determines the rating of a pump heater. The same applies to a gas heater too. But what makes pumps different is their amount of horsepower is also rated. The average size of a pump is 3.5 horsepower/75,000 BTUs, 5 horsepower/100,000 BTUs, and 6 horsepower/125,000 BTUs.

Heat pumps are great if you’d rather not purchase a solar  heater. Even though pumps cost more money initially, the long-term cost savings of operating the pump will make up for it. You should make your money back within two years.

Your home water can also be heated with a pump too. This can save you money on your normal indoor heating expenses.

Which Pool Heater is the the correct for Your Pool?

The pool heater that is top for your pool will depend on your location on the map and the heat source that your home has available.

Use a gas heater if you live in a northern state with natural gas access.

Use a pump if you live in a northern state without any natural gas access.

Use a solar heater or heat pump if you live in a southern state.

These various  heating systems can be purchased anywhere, but some are better to use in certain places than others. That is why we’ve made these recommendations.

If you’re on a tight budget, then a  pump and solar cover are recommended. This will cost you a bit of money initially but consider it a long-term investment that will save you money later.

Heater vs. Pump

Electricity is used to power both an electric heater and a heat pump. But these are different devices, though. Electric heaters use a hot coil to transfer heat to the pool water. Heat pumps transfer heat to pool water by taking the surrounding outside air and absorbing heat from it. Several components, including an air compressor, is used in a  pump.

Heat pumps are initially more expensive than electric  heaters. As for the monthly cost, pumps will save you up to 5 times the amount it would take to operate an electric or gas heater. Therefore, you’ll save more money as time goes on.

If  pumps are installed and maintained properly, you can get at least ten years out of them. This is a lot longer than you could get out of electric or gas heaters.

It is cheaper to purchase an electric  heater, but it’ll consume more electricity each month and raise your monthly power bill. But if you have an indoor spa, it can be used to heat that too. It all depends on what your specific needs are. In some cases, you might want to use both an electric heater and gas heater, especially for dealing with the cold winters or an indoor swimming pool.


We’ve presented you with some of the top-rated swimming pool warmers available. Of course, there are many other fabulous heaters available on the market too. The options available are almost endless. Our list has simply given you a place to start looking. Go through each one carefully and choose the top one which suits your needs.

Don’t let colder temperatures stop you from enjoying a nice and comfortable swim. A  heater can make this dream come true. If you elect to go ahead and purchase a heater, let me know in the comments or via email which unit did you get. I would love to hear your reviews and opinions about the top heater.


How Swimming Pool Heaters Work

The pool water heater circulates the water and causes it to flow towards the filter and pump heater. A heater does not produce heat. It extracts heat from the outside air and pushes it into the water. How does this happen? Simple.

The heater uses a fan to blow the outside air towards an evaporator coil. The fluid refrigerant internal the coil absorbs hotness from the air. The result is a warm gas which travels from the coil to the compressor. 

When the gas goes through the compressor, it becomes a much hotter gas. Once it leaves the compressor, the gas goes through the condenser. As the water circulates and passes through the pump, the condenser places the heat into the water. The circulation continues as the heated water goes back into the main pool area. It mixes with the cooler water and warms everything up. The hot gas becomes a liquid again after it leaves the condenser coil. After the liquid returns to the evaporator, the entire process repeats itself.  

A high-efficiency heat pump features scroll compressors. It will remain efficient if the outside temperature stays over 45°F. Cooler outside air forces the heater to consume more electricity. But you shouldn’t need to deal with this issue if you use your pool during warmer seasons, such as the summer. 

Choosing a Heating Appliance for Your Pool 

Heat pumps are more expensive than gas-powered swimming heaters. On the upside, pumps are more energy-efficient and cost less to operate each year. If you perform standard maintenance on your pump, its lifespan could easily surpass a gas heater’s lifespan. Then your long-term investment will pay off.

When you go shopping for a heater, you need to consider its size, energy efficiency, initial cost, and future costs. A certified technician can help you figure out the proper heater size for your pool. They will conduct a size analysis of your pool to come to this conclusion. 

The technician will consider your pool’s surface area, the average water temperature, and the average outside temperature. Other considerations include the average humidity levels, wind speeds, and nighttime coolness. For instance, if you live in a windy area with cooler nights and very little humidity, then you’ll need a bigger heater. 

Pool Heater Sizing 

Horsepower and BTU output are how pumps are rated. The most common pool warmer ratings include:

  • 5 Horsepower / 75,000 BTU
  • 5 Horsepower / 100,000 BTU
  • 6 Horsepower / 125,000 BTU

If you want to calculate the appropriate heater size for your pool, take the following steps:

  • Figure out which temperature you’d like for your pool water
  • Figure out the average temperature during the coldest time of the year when you use the pool.
  • Figure out the difference between the average cold temperature and your desired temperature. The answer is the “temperature rise,” or the amount you need to raise the temperature to achieve your desired temperature goal.
  • The pool surface area is calculated in square feet.
  • Calculate the BTU per hour output needed for the heater. You can do this with the following formula: Pool Area * Temperature Rise * 12 

Pool Heat Energy Efficiency

The coefficient of performance (or COP) is how a pump’s energy efficiency is calculated. If you have a high COP, it means your pump is incredibly energy efficient. If you have a low COP, it means your pump is not so energy efficient. 

There is no set formula for calculating the COP. That is why it is not realistic to compare the COP numbers of various pump models. The only way this would be acceptable is if their manufacturers conducted the same test to determine the COP. Most manufacturers test the heat pump with 80°F pool water and 80°F outdoor temperature. 

The COP number is usually something between 3.0 and 7.0. It is the equivalent of between 300% and 700% efficiency. In other words, each electricity unit needed for the compressor will give you 3 to 7 heat units from your pump. 


Always have a qualified technician install your pumps. You may also need to hire an electrician to handle the electrical wiring hookup. Sometimes the technician has this qualification too. 


Don’t forget about pool maintenance. If you want your pump to last a long time, you need to perform maintenance regularly. Maintenance also includes any repairs that need to get done.

If you have questions about maintenance, you can always read the owner’s instruction manual included with the pool warmer. It’ll let you know how often to perform maintenance checks and other recommendations.

A tune-up is recommended once a year at least. Again, hire a professional for any mechanical tune-ups needed. If you do everything correctly, you should get at least ten years out of your pool heater. 



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