We can all agree that nobody enjoys swimming in a cold pool. Even if you’re living in a warm and sunny area, you can only count on enough natural heat during the summer peak. If you’re in a colder climate or you simply want to extend the swimming season, you should consider getting a pool heater.

Three types of pool heaters are available on the market today – gas, solar, and electric. While they all serve the same purpose (heating the pool water), the way they operate is very different. Finding the best pool heater depends on many factors including pool size and climate, so one of these types might be better for your pool than others.

Since pool heaters are fairly expensive, our buying guide explains what each heater can do as well as its downsides. And, whether you’re after the best pool heater for above or in-ground models, the guide takes the budget into consideration too. If you need something reliable and efficient straight away, check out the best inground pool heaters we carefully selected for our list.

How To Choose The Best Pool Heater – Buying Guide


Types of Pool Heaters – Advantages and Disadvantages

Like we mentioned at the beginning, there are three types of pool heaters – gas, electric, and solar. The main difference between them is the energy source they use to heat the water. As you can probably guess, each type has some pros and cons. Take a look at what each of them has to offer.

Natural & Propane Gas Pool Heaters

This type is probably the most efficient and warms the water fastest. Basically, the unit connects to a natural gas line (or a propane tank) and uses a gas burner to warm up water pipes that pass through. However, it gives out emissions as a result of this process, and some high NOx models are not allowed in certain areas (mainly California and Texas).

While these pool heaters are fairly affordable to buy, they are currently the most expensive to run on a monthly basis. For the time being, we would recommend a solar or electric pump. However, if gas prices come down, these pumps might become cheaper to run than electric ones and might gain back their popularity.

Solar Pool Heaters

Solar pool heaters rely on solar energy to heat up the pool water. The cold water from the pump goes through the tubing on the solar panels and is warmed up in transition before getting back to the pool. Even though they are relatively new in the pool heating world, the technology is improving all the time. However, if you plan to heat your pool on solar power, there are some positive and negative aspects you should know about.

The good news is that there are almost no maintenance costs once you have the heater installed. There are no monthly operating costs either. Once you install the panels, they will convert sunlight into heat for free. Of course, they are also the most environmentally-friendly option.

The bad news is that solar pool heaters are the most expensive type to buy and install. Another negative is that they are often very slow. They rely on long sunny hours to do their job, and won’t be very effective on cloudy days or during the night. Still, they will significantly reduce the heating costs even if you combine them with another heater.

Electric Pool Heaters (Heat Pumps)

Electric pool heaters are very consistent and energy-efficient which is why they are one of the most popular pool heaters on the market. The higher-rated heater you choose, the less money you will spend per month. Electric pool heaters are also known as heat pumps because of the way they operate.

Heat pumps use warm outside air to warm up the liquid refrigerant inside a coil. As it gets warmed up, it turns into a gas and passes through the compressor to raise the temperature even higher. Afterward, the gas pipes go through the condenser where they transfer the heat to the pool water, cool down (become liquid again), and the process starts over.

The great thing about these is that they don’t require much energy and have no harmful emissions. However, they greatly depend on outdoor temperature (to warm up the gas) and won’t work well when it’s cold outside. A huge benefit of heat pumps is that they have excellent longevity and will outlast almost any other heater. If taken care of, these pumps can last for 10 to 20 years.

As an alternative, you also have traditional electric pool heaters. They work similarly to water heaters most of us have at home (electrically heated coil in a water tank). While they can be a bit faster, they often produce higher costs, both initially and in the longer run.

Gas vs Electric Pool Heater – Comparison

Gas and electric heaters are the most common solutions for heating a pool. Even if you have a solar heater installed, there is a good chance that you will have one of these as a backup. This is why we think it’s useful to sum up the pros and cons of both, so you’ll have an easier time deciding.

Gas pool heaters:

  • Fastest and most efficient water heating
  • Great for warming up very cold water
  • Independent from outside temperature (good for winter)
  • Have emissions as a byproduct
  • Last 5 to 10 years (if maintained)
  • Cost less initially but much more to run

Electric pool heaters:

  • No harmful emissions when running
  • Great for maintaining pool heat
  • Cost much less in the long run
  • Last 10 to 20 years on average
  • Dependent on outside temperature (better for summer)
  • A bit slower than natural gas pool heaters

Sizing A Pool Heater

Properly sizing your heater is essential for having warm water throughout the season (and perhaps a few months more). However, doing this is not very simple as several different factors influence the calculations. These include pool surface area and volume, ambient air temperature in coldest conditions, as well as targeted water temperature.

Subsequently, if the heater is not powerful enough, you will not be able to reach the desired temperature. On the other hand, if it’s too powerful, you could be wasting a lot of money and not running the heater efficiently.

Surface Area and Volume of Your Pool

The size of your pool will determine the heater size you need. It’s logical that a larger pool will require a heater with more BTUs. Two things come into play here – surface area and volume. A pool with a large surface area will lose heat faster, meaning that it needs a stronger heater to maintain the temperature. Similarly, higher volume means there is more water to be heated.

You calculate the surface area by multiplying the length and width of your pool. If you have an irregularly-shaped pool or an above ground pool, you probably have this information in the building specs or the user manual. The same goes for the volume. When you have these numbers, you can make BTU calculations, as we’ll explain a bit later.

Difference between air and water temperature (temperature rise)

Lower air temperature means that the water loses heat faster. In this situation, you will need a more powerful heater to reach the desired temperature in a reasonable time. Also, sufficient power is required to maintain the water temperature once you reach it. On a related note, we advise that you also get a pool cover for extra insulation.

If you want your pool heated quickly, you’ll have to spend a bit more on a heater. As mentioned earlier, gas pool heaters are the fastest, while electric heaters are a bit slower (but more energy efficient). Solar-powered heaters are the slowest, so you’ll have to buy large panels if you want to warm the pool quickly.

BTU calculations

The power of your new heater is calculated in BTUs (British Thermal Units). One BTU is the amount of heat needed to increase the temperature of 1 pound of water by 1°F. The BTU rating of your heater shows you how much water it can heat and how quickly. These calculations refer to gas and electric heaters.

If you’re calculating volume using gallons, you should know that one US gallon of water translates to 8.35 pounds. For example, an in-ground pool that measures 15 x 30 x 8 feet has 3600ft3 of water (26,930 gallons, or roughly 225,000 pounds of water). This presents the total amount of water that needs to be heated. So, for raising the temperature for 1°F, this pool will need 225,000 BTUs of heater power. For easier calculations for any pool, 1 cubic foot (ft3) translates to 62.43 pounds.

Next, you have to take the temperature difference into account. Let’s say that you want to raise the pool heat from 50 to 80°F (30 degrees difference). This means that the total number of BTUs to do this (for the pool we used as an example) would be 225,000 x 30 = 6,750,500.

When buying a heater, it’s expected that it can achieve the target temperature in 24 to 72 hours. We’ll use the 24-hour mark for our example. Of course, a smaller heater can also achieve the target temperature – it will just require more time.

So, if our target BTU output is 6,750,500 (for 24 hours), this means that the heater power we need is 6,750,500 / 24 = 281,000 BTUs. In other words, a 281,000 BTU heater can warm up a 27,000-gallon pool from 50 to 80 degrees in 24 hours. To calculate this for your pool, you can use this formula:

Volume (in pounds) x Temperature difference / Time to heat = Required BTU output per hour

Once heated, maintaining the pool heat requires a lot less power. On the other hand, if you live in a windy area, the water will cool faster. These are just rough calculations, and you should adapt them to your situation. Some people choose to go with a smaller (more economic) heater and don’t mind waiting more if that means saving a lot of money.

As for solar heaters, their size is calculated differently. Depending on the climate you live in, the panel surface needs to match 70% of the pool surface area (sunny climate), or up to 100% (less sun). Variables like sun exposure and cloudy days also influence this, which is why you need to take all of these into account when making an estimate. 

Type of Pool: In-ground vs Above Ground

Choosing the right type of heater will also depend on whether you have an in-ground or an above ground pool. There are specific heaters for both and, while some are interchangeable, most will work only with one or the other. The main differences between them are in size and capacity, but the pipe connections may also be different.

For example, the best above ground pool heaters are usually much smaller and more energy-efficient than those made for in-ground pools. Because of this, always make sure to check whether the heater is compatible with your pool.

Initial and Running Costs (Budget)

Total costs for a heater can make or break a deal, regardless of how well it works. While none of these are very cheap, there can be significant differences in cost between different types and models. Of course, a larger pool will require a more powerful heater that will end up costing more money. But let’s go through the costs for each type of heater.

Gas heaters are probably the most affordable to buy (relative to their power). For a decent initial sum, you can buy a great heater even for a larger pool. However, these are the most expensive in the long run. Natural gas costs a lot of money, not to mention using propane tanks. Also, gas prices tend to vary a lot, so you can’t be sure about future expenses.

Electric heaters fall somewhere in the middle. While they are a bit more expensive initially, they cost less to run so it evens out after a while. Finally, solar heaters are the most expensive to install. If you have a large in-ground pool, buying and installing solar panels might cost you several thousand dollars. However, that’s about it, because they have no running costs and will pay off after a few years.

Durability and Warranty Coverage

One of the big concerns when buying pool heaters is how long they are going to last. A gas pool heater is the least durable, usually lasting 5 to 10 years (with proper maintenance). Electric heaters are a bit more durable, and most can easily last for 10 years. Sun-powered heaters are the most durable, with the best swimming pool heaters lasting up to 20 or more years.

The warranty reflects the projected durability. A natural gas pool heater the shortest warranty (on average), while solar heaters often have generous 10-year warranties. Unfortunately, most warranties only offer limited coverage, so we advise that you take a good look for each product. For example, bad water chemistry or installation by an unlicenced person might void the warranty.



Q: Can I Install A Pool Heater On My Own?


The short answer is yes. If you are confident in your abilities and follow the instructions exactly, you can certainly install a heater on your own. The only problem is that if something goes wrong, you may not be covered by the warranty, which could end up costing a lot. On the other hand, if you successfully install the heater by yourself, it also saves you a lot of money.

Q: Can Solar Heaters Be Used For Anything Else?


While solar heaters do come with solar panels, these panels are specially configured to connect to your pool pump system and heat the water in your pool. It is our opinion that solar heaters should not be used for anything else.

This being said, it is sometimes possible to reconfigure the panel and power something else (if you know what you’re doing). Still, this brings an increased risk of breaking the panels and the heater.

Q: Are Pool Heaters Efficient Or Environmentally Friendly?


That depends on the type of heater you choose. For example, a gas pool heater is not very environmentally friendly or efficient. It runs on natural gas (natural resource), and the heater creates harmful emissions. While some are low NOx, they are still behind the alternatives from the environmental aspect.

Electric heaters are somewhere in the middle on both points. They are not the most environmentally friendly, but they are not the worst. The same goes for their efficiency. The most ’green’ option you can get are solar heaters. While these cost more to buy, they don’t require anything but sunlight and don’t have any emissions.

Q: Are Pool Heaters Noisy?


Like most other things, it depends on the type and model you’re using. An electric heater might not make any noise at all, especially the more expensive ones. On the other hand, both a solar and a gas pool heater can make some noise depending on the model. Still, this varies from product to product and you should check for each one if this is a concern.

Q: How Much Propane Does A Pool Heater Use?


That is a hard question to answer without knowing the type of propane heater you are using, the size of your pool, and the target temperature. If you are heating your pool from cold to hot, you could use up to 4 gallons per hour. You will use a lot less to keep it at the desired temperature.

Q: How Fast Do Pool Heaters Work?


It depends on the heater type, pool size, as well as water and air temperature. This being said, a heat pump (like the ones we reviewed) takes anywhere between 24 and 72 hours to raise the water temperature by 20°F, depending on the variables we mentioned. A gas pool heater will do the job faster but costs more to run, while a solar-powered heater is slower and less reliable on cloudy days. 

Q: How To Heat Pool Faster?


There are several ways to get a pool warm faster. First, when building (or setting up) a pool, think about proper placement so it gets a lot of sun exposure. Next, choose darker pool liners because they absorb more heat and indirectly warm up the pool water. Finally, consider getting a solar pool cover that absorbs sunlight and transfers the heat to the water.

Q: How Much Does It Cost To Run A Pool Heater?


This depends on the type of heater you have. A 100,000Btu natural gas heater uses one therm per hour, which comes down to around $1.5 to $2 per hour (depending on the gas price in your area). As for electric heaters, it depends on their wattage. For example, the Hayward CSPAXI11 heater we featured requires 11 kilowatts. Given that electricity costs 13.31¢ per kilowatt-hour, running this heater costs around $1.46.

Q: Should I Leave Pool Heater On Overnight?


No, you don’t have to do this. You can, of course, but this will waste a lot of heat and significantly increase the bill. Heat loss increases with a greater temperature difference, meaning the heater will use even more natural gas or electricity to maintain the temperature during the night. To retain heat without wasting money, we suggest you get a thermal pool cover.

Q: Do Solar Pool Heaters Work In Winter?


Yes, but not as efficiently. Because there is less sunlight during the day, the sun angles are different, and the air temperature is much lower, a solar heater won’t be able to warm up the pool on its own. In fact, it can only provide around 20% of the needed heat, so you’ll have to use a gas pool heater if you want to swim during the winter.

Q: Do Solar Water Heaters Work At Night?


Since they rely on sunlight to heat the water, a solar heater for pool cannot warm up water during the night. However, if the system has an insulated water tank for storing hot water, it can add it to the pool during the night too. Still, most solar-powered heaters are backed up by natural gas or electric heaters for using during nighttime or on cloudy days.

Q: How Do You Protect A Pool Heater?


Taking proper care of your heater means fewer issues, less maintenance and, ultimately, less money in the long term. Here are some useful tips to protect your heater:

  • Keep the pool chemistry balanced (pH between 7.2 and 7.8, chlorine up to 10ppm)
  • Make sure to closely follow installation instructions (or have a professional install it)
  • Make sure the metal casing is electrically bonded (prevents shocks and short circuits)
  • Prevent any backflow into the heater (install a safety valve after the heater)
  • Make sure the pool pump has sufficient power to provide a good flow

A well-maintained heater will last for a long time. If you ever notice that there is anything wrong with it (not working properly, making funny noises), have someone come and take a look as soon as possible to prevent expensive repairs.

Globo Surf Overview

A heater for pools is a great way to extend the summer season and make the pool more enjoyable. Since this is not something you buy every day (and it’s also very costly), you should precisely calculate your heating needs and find the best pool heater that can get the job done.

Hopefully, our guide has given you the pointers you need so you never have to swim in cold water again. Believe us when we say that a heated swimming pool is guaranteed to become a great source of fun for friends and family.

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My name is David Hamburg. I am an avid water sports fan who enjoys paddle boarding, surfing, scuba diving, and kite surfing. Anything with a board or chance I can get in the water I love! I am such a big fan I decided to start this website to review all my favorite products and some others. Hope you enjoy!