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Best pool heaters 2021

Best pool heaters 2021
(Image credit: ShutterStock)

The best pool heaters will make sure that you never have to worry about the water being too nippy the next time you go for a swim. Rather than leaving the temperature up to chance, the best pool heaters 2021 will let you dictate your ideal temperature in advance, avoiding a lukewarm or freezing cold plunge for you and your guests.

While the best pool heaters will cost you a fair bit, the payoff is worth it, thanks to the speedy way they turn up the temperature. While the best electric pool heater is more sustainable, gas-powered units will rocket your temperature quicker. You’ll want to keep your eye on the unit’s power too, as a higher number of British Thermal Units (BTU) will mean it’s capable of turning your water toasty quicker. While gas options are speedier, they also tend to weigh more. So, if setting up a heavy unit sounds out of your comfort zone, you’ll want a lightweight heater for an easier installation.

Our guide rounds up the best pool heaters from Pentair, Hayward, and other brands that will perform under pressure. From our gas and electric pool heater reviews, you’ll realize that if you’ve got a large budget and an eye for clever, tech-savvy features, features such as digital temperature controls and eco-friendly heaters powered by solar will be at your disposal. However, if you’re abiding by a stricter budget, we’d suggest sticking to the best pool heaters 2021 that cover the basics such as a high BTU and a compact, lightweight design for easy installation.

For more water-based relaxation, check out our guide to the best hot tubs and the best swim spas too.

1. Pentair 460737 MasterTemp: Best propane pool heater

Best pool heaters: Pentair 460737 MasterTemp

(Image credit: Pentair )

The best energy efficient propane gas pool heater

Dimensions: 36 x 25 x 30-inches
Fuel type: Propane Gas
Weighs: 128 pounds
Reasons to buy
+Best-in-class energy efficiency+Low NOx emission+Digital display
Reasons to avoid

This propane gas pool heater heats up quickly so you won’t have to wait around for hours before taking the plunge. It’s certified for low NOx emission and outperforms industry standards. It has a rotating digital display so it’s easy to view, and user-friendly indicator lights help make it easy to both operate and monitor performance. 

The tough, rustproof exterior is designed to withstand all weathers, extending its longevity. The compact design and quiet operation mean you can swim in peace – it hardly makes a sound, so it won’t intrude on your poolside enjoyment.

2. EcoSmart Smart Pool 18: Best electric pool heater

Best pool heaters: EcoSmart SMART POOL 18

(Image credit: EcoSmart )

The best electric, tankless water heater

Dimensions: 6 x 14 x 17-inches
Fuel type: Electric
Weighs: 24.5lb
Reasons to buy
+Compact+Digital temperature control+Energy-efficient
Reasons to avoid
-Complex to install

This differs from other electric pool heaters in so far as it’s an electric tankless heater. Instead of traditional pressure switch activation, the EcoSmart Smart Pool 18 uses flow sensor technology, which increases its reliability and longevity and also reduces the risk of elements burning out. 

The EcoSmart Smart Pool 18 electric pool heater has a digital temperature display and dial that lets you set your preferred water temperature in 1-degree increments. It can be used as an alternative to a heat pump or as a booster. It’s compact and lightweight, and it’s energy-efficient – no matter what the ambient temperature.

3. Hayward HeatPro HP21404T: Most economical pool heater

Best pool heaters: Hayward HeatPro HP21404T

(Image credit: Hayward)

Save up to 80% on your pool operating costs

Dimensions: 32 x 43 x 40-inches
Fuel type: Electric
Weighs: 250 pounds
Reasons to buy
Reasons to avoid
-Not as fast as a gas heater

This HeatPro electric heat pump is ideal if you’re looking for an electric pool heater that will allow you to extend your pool season. It uses the outside air together with a titanium heat exchanger and profiled fan blade to generate heat for a fraction of the cost of gas pool heaters. 

The manufacturers say you could save up to 80% on your pool operating costs. As well as being energy efficient, it’s also easy to install and quiet to run, so you can enjoy your pool and backyard without the intrusion associated with a noisy pool heater.

4. Hayward H-Series H250FDN: Best natural gas pool heater

Best pool heaters: Hayward H250FDP Universal H-Series 250,000

(Image credit: Hayward )

High performance natural gas pool heater with low NOx emissions

Dimensions: 29.5 x 24 x 25-inches
Fuel type: Natural gas
Weighs: 165lb
Reasons to buy
+Low NOx emissions+Salt water and chemical corrosion resistance
Reasons to avoid

The Hayward H-Series H250FDN is an energy efficient, high performance natural gas pool heater. The hydraulic design reduces circulation pump run time. It’s an environmentally friendly option for a gas heater as it produces low NOx emissions. 

This heater has a standard cupro nickel heat exchanger and offers ultimate installation flexibility on new or existing equipment pads. The forced draft system moves air through the combustion chamber at a precise flow rate, eliminating the outside weather variables that can affect the performance of a gas pool heater.

5. SmartPool SunHeater S120U: Best solar pool heater

Best pool heaters: SunHeater S120U

(Image credit: SunHeater)

Heat your pool with the power of the sun

Dimensions: 120 x 27.5 x 16-inches
Fuel type: Solar
Weighs: 17.5lbs
Reasons to buy
+Easy to install 
Reasons to avoid
-Requires long hours of sunlight

If you’re looking for an eco-friendly, cost-effective way to heat your pool, we think this is it. The universal system is suitable for in-ground or above ground pools, and this solar pool heater could not be easier to install – it’s designed to be placed on your roof, ground or fence, and it works in conjunction with your existing pool pump. 

This solar pool heater captures heat from the sun’s rays and can raise the temperature of the water in your pool by 6-10 degrees Fahrenheit, adding weeks to your pool season.

Best pool heaters FAQ

Which type of pool heater should you choose?

Understanding how each type of pool heater works isn’t rocket science but a basic grasp of the logistics will help you choose the best heater for your pool. There are three main types of pool heaters; gas pool heaters, electric pool heaters (including heat pumps) and solar powered pool heaters. 

The difference between them is the power source they use, but this affects everything from the installation process to the running costs, as well as which climates they are appropriate for.

Gas pool heaters

A gas pool heater runs in a similar way to your home’s hot water heater – it burns natural gas or propane in a combustion chamber and transfers that heat to the water as it circulates through the heater. It has to be connected to a gas line through an underground gas pipe. This means that while the initial upfront cost may be lower than other types of pool heater, the installation costs are usually higher. And depending on the location of your nearest gas source, installation can even be prohibitively costly. 

In addition to the added installation cost, the ongoing running cost of a gas pool heater is higher. The price of gas, which fluctuates, will determine the exact ongoing cost of running a gas pool heater.

Gas pool heaters are more powerful than other types of pool heater, so they’re good for heating bigger pools that hold a large volume of water, and useful if you want to heat your pool in a hurry. They’re also ideal if you live in a cooler climate, or if you intend to heat the pool occasionally and for short periods. If you’re looking for an eco-friendly way to heat your pool, however, a gas pool heater is not the answer.

Solar Pool Heaters

A solar pool heater is the most planet-friendly way to heat your pool. Unlike other types of pool heater, solar pool heaters use natural energy sources, making them the most economical option. A solar pool heater uses solar collectors to transfer the thermal energy of the sun to the water in the pool. 

You place the solar collectors near to the pool pump, so the heat is transferred to the water as it’s pumped into the pool. Once you’ve installed a solar pool heater, you’ll have almost no maintenance costs and no monthly operating costs. Once the panels are in place, you can sit back and let the sun do its job.

A solar pool heater is very easy to install. They don’t need to be connected to any kind of energy outlet, so you won’t need to hire an installer. They work slowly compared to a gas pool heater, but once the pool reaches the desired temperature, it’s easy to keep it there – just remember to ensure that both your pool and the solar collectors get plenty of sunlight and aren’t located in a shaded area. 

This type of heater is best suited to warmer climates that get plenty of sun. If you want to use the pool at night without experiencing colder water, you may need to purchase a diverter, so factor in the additional cost of this.

Electric Pool Heaters

As you might expect, electric pool heaters are the most popular type of pool heater, and arguably the most efficient. As well as performing consistently year-round, an electric pool heater is the fastest way to heat your pool. You’ll obviously have monthly costs with an electric pool heater – factor in that your electricity bill will go up – but you’ll spend less per month if you go for an energy-efficient electric pool heater, compared to one that’s cheaper to buy but has higher running costs.

Electric heat pumps are more eco-friendly than gas pool heaters as they use the ambient temperature to heat the water. They don’t need to be connected to a gas line, so they're also easier to install than gas pool heaters. Electric heat pumps raise your pool’s temperature less quickly than gas pool heaters, but they can be kept running longer for less money, so they’re more cost-effective if you want to use your pool every day.

How does climate affect your pool heater?

Climate is already a huge factor in how often you’ll use your pool, but how does it apply to your heater? Well, some types of pool heater rely heavily on the ambient temperature of the pool, or sunlight in the case of solar models, in order to function. So, there’s a very dependent relationship between some models and climate. 

Make sure you factor this into any of your buying decisions and calculations when it comes to pool heaters. If you live in a region with a steady, hot climate, then you’ll be fine to opt for a heater that’s reliant on the ambient temperature. If the climate where you live tends to be a little more temperamental, then you may want to avoid those kinds of models, so you can get more out of your pool, and enjoy it even on days when the sun doesn’t shine. 

What size pool heater should you get?

Whether you want a gas, electric or solar pool heater, choosing the correct size heater for your pool is important. Gas and electric heaters are measured in BTU, or British Thermal Units. That’s the amount of energy it takes to raise one pound of water by one degree. 

The more you have to raise the temperature by, the more energy you need. It’s worth checking out one of the helpful calculators online to help you calculate the BTU you need in a pool heater. Consult a pool pro for more specific guidance.

What are pool heater thermal units?

As with other household and outdoor products that generate heat, such as gas ranges, for example, all pool heaters are sized by British Thermal Unit (BTU). As a rough calculation, it takes one BTU to increase the temperature of 1lb of water by one degree Fahrenheit.

The best pool heaters vary from 75,000 BTU up to a whopping, commercial grade 450,000 BTU for really big pools, and obviously the higher the BTU, the more expensive the pool heater. 

How long do pool heaters last?

Investing in a pool heater can be a costly business, and you’re probably trying to factor in just how much use you can get from this purchase over the years. The good news is that pool heaters are designed to last between seven to ten years, so you shouldn’t have to fork out on a new one anytime soon. However, the lifespan of your pool heater is of course dependent on how well it’s maintained, as well as how healthy your pool water is. Getting into a good routine with pool cleaning is essential, as well as keeping an eye on chemical levels below the surface. 

What’s the best pool heater for you, and are they worth it?

Your ideal pool heater will be dictated by where you live and what heat source you have available, such as gas, an electric heater or a solar pool heater – a good choice if you live in sunnier climes with regular sunshine. 

Pool heaters with solar covers are usually cheaper in the long run and can help keep your costs down over the years to come, though the initial outlay is usually a little pricier compared to a standard electric pool heater.

Are pool heaters worth it? In our opinion, yes. Even if you live in a state that’s pretty warm and sunny for most of the year, there will still be days when the water temperature is less than inviting. A good pool heater will ensure your home pool stays open year round, so you can enjoy it much more and get your money’s worth.

Becks is a freelance lifestyle writer. She started her career in print journalism at a local newspaper and has since then worked across digital and social media for food titles and home interior magazines. When she’s not writing, she’s reading and when she’s not reading, she’s writing.