How to Heat a Swimming Pool

Whether you're looking to add a few weeks to either end of pool season, or you're wanting to keep the water at a comfortably warm temperature year-round, the best way to do that is to add heat to the pool. Luckily, there are many ways you can do that. Depending on your pool size, equipment setup, utilities available, budget, and personal preferences, there are heating options available for virtually every pool. Adding heat to the water is a sure-fire way to help you get more enjoyment from your pool. Let's go over the different heating options on the market to help decide which one's right for you.

Gas Heaters

First up are the gas pool heaters, which are the most common type of pool heater. If you're looking for quick and efficient heating with a large temperature differential, a gas heater might be the right choice for you. Gas heaters use either natural gas or propane to generate heat. That heat is then transferred to the pool water through a heat exchanger. Gas heaters can heat your pool or spa rapidly, making them ideal for on-demand heating needs.

They’re less expensive than heat pumps to purchase. However, their high cost to operate can be a limiting factor in how often it gets used. On average, gas heaters cost anywhere between $3 and $9 per hour to heat the water. Because they work well in any temperature or climate, they’re popular in cooler regions that have very brief swimming seasons.

In general, you can expect an increase of 1ºF to 2ºF per hour (24ºF to 30ºF per day) with a gas heater. Gas heaters paired with a smaller water volume, such as a hot tub, can warm the water much faster. A properly sized gas heater will have no problem providing a 20ºF to 30ºF temperature differential or more.

Heat Pumps

Next, we have heat pumps. Heat pumps are among the more expensive pool heating options to purchase. However, they make up for it in their low run cost, making them a great choice for long-term savings. Although heat pumps run on electricity, don't confuse them with electric swimming pool heaters, which aren’t very common among homeowners.

Heat pumps work by extracting heat from the air surrounding the unit. How does this work? Well, the technology is remarkably similar to your home's air conditioner. As air moves over the coils, the refrigerant inside the coils absorbs the air's warmth, which gets transferred to your pool water. Because heat pumps require warm air to function, they work most efficiently in temperatures above 50 degrees Fahrenheit. For this reason, they’re extremely popular in warmer climates. Because heat pumps can’t warm the water as quickly as a gas heater — especially in a large pool — they're most ideal for maintaining a consistent, comfortable water temperature. Some pool owners use both a gas heater and a heat pump. This approach warms the water quickly (gas heater), then maintains that warmth at a lower cost (heat pump).

Most heat pump users can expect a temperature increase of 6ºF to 20ºF per day. The available temperature differential depends on a few factors, including the ambient air temperature. However, most properly sized heat pumps are capable of warming the water by at least 20ºF or more. Keep in mind that these estimates are largely dependent on BTU output and pool size. The outside temperature also plays a role in how much heat can be transferred.

DID YOU KNOW? Some models of heat pumps are reversible, meaning they can also cool your pool water. This comes in handy when it gets hot in the summertime! If you live in a warmer climate with hot summers and mild winters, and you want the most consistent water temperature year-round, a multifunctional heat-cool heat pump is the way to go.

Solar Heaters

Now let’s talk about solar. A solar pool heater is one of the most environmentally friendly and cost-effective ways to heat your pool. There are a few different styles, all of which harness the sun’s warmth to heat the pool water.

The most popular method is to use solar panels. These are typically installed on the roof or on a sunny area of the lawn beside the pool. Panels come in all kinds of shapes and sizes. If you have an above ground pool, a solar heater is the most popular because it's fairly easy to integrate with your equipment. The water moves slowly through a series of tubes within the panel(s), allowing the water to absorb the sun's heat energy before returning to the pool.

Another method involves using a pool return adapter. Use it to connect the return to one end of a garden hose. Next, coil up the length of the hose on the pool deck, and stick the other end of the garden hose back into the pool. Water will flow through the hose slowly, warming up in the hose before returning to the pool. Darker hoses generate more heat with this method, but any hose color will work.

In both scenarios, it’s the same concept as when you leave a garden hose laying out in the sun. The water inside the hose gets hot VERY quickly! You can feel that intense warmth when you turn the hose back on again. The sun can be a powerful, yet completely natural, heating solution for your pool water.

The amount of heat you'll get from a solar heater depends on the surface area of the heater in relation to the surface area of the pool. It also depends on weather conditions and how much direct sun exposure the panels, tubes, or hoses receive. In most cases, pool owners using a solar heater can expect a 2ºF to 4ºF temperature increase per day, up to 10ºF total. Larger rooftop panels can potentially add even more warmth when conditions are right.

Solar Pool Covers

Finally, let’s talk about solar pool covers. Much like solar heaters, solar covers can trap heat energy from the sun and transfer it into the pool water. Solar pool covers also help to reduce evaporation by as much as 95%. Not only does this conserve water and reduce chemical usage, it also prevents evaporative heat loss, which is the leading cause of heat loss in a pool.

Solar covers are the best tool for keeping heat in the pool. Think of it like putting a jacket or cozy quilt on the water's surface to insulate the water. There’s a reason these are also called solar “blankets" — because it helps keep the heat in!

Used on its own, a solar cover can easily add 10ºF to 15ºF or more to your pool water at a rate of 2ºF to 5ºF per day. But when used with another heat source, such as a gas heater, heat pump, or solar heater, a solar cover is even more valuable. It can greatly improve heating efficiency, accelerate your pool heating efforts, and save you significant money in heat energy costs. Solar covers are also very affordable to purchase, and the water, chemical, and energy savings it provides can help the cover pay for itself over the course of just one or two swim seasons.

BONUS TIP: Because of its size, solar covers can be challenging to install or remove from the pool on your own. Using a solar reel makes the job much easier!

What's the Best Way to Heat a Swimming Pool?

Heating the pool helps keep the water comfortable so you can extend the swimming season or enjoy your pool year-round. Choosing the right heating method for your swimming pool depends on several factors, including climate, budget, installation obstacles, and personal preference. Consider the size of your pool, desired water temperature, how frequently you use the pool, and your monthly heating budget when making your final decision.

You can also use more than one heating method to maximize heating efficiency and total warmth output. Doubling — or even tripling — up on heating methods helps speed up heating time and even save money on heating expenses. As mentioned above, some pool owners have both a gas heater and a heat pump on their equipment pad. The gas heater heats the water quickly or provides an extra boost as needed, while the heat pump helps maintain the heat for a much lower cost than running the gas heater the entire time. Adding a solar pool heater can also supplement your heating efforts with natural, renewable energy. And to top it all off, a solar cover is a must-have for any pool owner — it's a viable source of standalone heat, or it can help save you money on heat energy costs when using conventional heating methods.

If you have any other questions about swimming pool heating solutions, call or stop by your local Leslie’s. And for more tips and tricks on pool heating and pool care, check out the other pool heating articles in our Resource Center.