Dive into the Warmth: How Pool Heaters Work

Summer doesn’t last nearly long enough for swimmers and water lovers. With the shorter days, the water temperature drops, and not too many of us enjoy losing our breath when we dive into the pool. But pool heaters can help extend the swimming season, sometimes year-round. Some can up the temperature quite substantially. How do pool heaters work, then?

Most pool heaters work by passing heat to the pool water via a heat exchanger. Various pool heaters are available, including heat pumps and those using gas, electric, or solar power. Regardless of their heating methods, all systems draw the water from the pool, heat it, and return it to the pool.

A pool heater can be a valuable addition to any swimming pool. It regulates the water temperature and makes swimming more enjoyable as summer dwindles into fall and perhaps beyond. Pool heaters use different types of technology to warm your pool water. Let’s find out how each type works.

Types Of Pool Heaters And How They Work

If you’re interested in installing a pool heater but are still deciding which type to purchase, knowing how each one works will help you decide. They vary in cost and efficiency, and some heating systems only suit certain climates. Once you have an overview of their inner workings and how that applies to your needs, you can make an informed choice.

How Heat Pump Pool Heaters Work

Sometimes people lump electric pool heaters and heat pump pool heaters under the same category, but they function differently, although they both use electricity to power them. Here we will separate the two.

A heat pump uses minimal energy to transfer heat from one space to another. Heat pumps transfer ambient air from outside to the pool water, and since they use “ready-made” heat, they use less electricity than other types.

As the pool water flows through the pool pump, it travels through the filter and the heat pump. The heat pump’s fan pulls in warm air from outside and sends it to the evaporator coil. Liquid Freon within the evaporator coil absorbs the heat, transforming the liquid into a gas. This warm gas then travels through the compressor, which heats it even further before it flows through the condenser.

The condenser warms up the cool water by 3°-5°F before it returns to the pool. The hot gas becomes a liquid again and returns to the evaporator to start the process over again.

Heat pump pool heaters work well in areas with average temperatures above 45°-50°F. The colder the air that gets drawn in, the harder the heat pump must work to heat the water, making it less efficient and more energy-hungry.

It can take days for the heat pump to warm the water, but once it has reached the optimal temperature, the pool heat pump is very effective at maintaining it. Although heat pump pool heaters are expensive to install, they can save you money in the long term if you live in an area with a warm climate, and even better if there is high humidity.

How Electric Pool Heaters Operate

The other type of electric pool heater, also known as a direct flow heater, differs from the heat pump by using water as its source instead of air. These pool heaters use an electric element to warm water, similar to the one used in an electric water heater.

The heater is connected to the pool pump’s return flow pipe so the pump can propel the water over the element. Electricity heats up the element, which transfers some of its heat to the water. As the water circulates, it gradually raises the pool’s temperature. It can take a day or two to achieve the desired temperature.

Electric pool heaters are expensive to purchase and are also usually costly to install because of the wiring that needs to be done. This type of heater could skyrocket your energy bill because the best way to have your pool at a constantly warm temperature is to run the pool heater overnight, which will chew through a lot of electricity.

But an electric pool heater is the most reliable method of heating your pool, emits no pollution, and has a long lifespan.

How Gas Heaters Work

A gas heater is the most powerful pool heating option. It can raise the water temperature quickly, even when it’s cold outside.

These heaters use propane or natural gas to heat the water. The pool pump propels the water into the filter and then sends it to the heater. Gas burns in the combustion chamber, warming the water, which then returns to the pool.

If you don’t have access to natural gas, you will have to purchase a massive propane tank to install in your pool area. It’s best to buy the biggest gas heater you can afford because it will heat your pool quickly. It can raise temperatures by 1°F in an hour. But the advantage of these pool heaters is that you only need to run them when you want to swim.

Still, they are more expensive to operate on a day-to-day basis, their lifespans are shorter than electric pool heaters, and they require more maintenance.

The Workings Of Solar Pool Heaters

Pool heating systems that use solar power consist of the following:

  • Solar collectors
  • Filter
  • Pump
  • Flow-control valves

The pump first propels the water through the filter to pick up any debris, and then the flow-control valves divert it to travel through the solar collectors. The collectors are installed where they receive the maximum sunlight during the day. They transfer their heat to the water, which then returns to the pool.

Solar pool heaters are the most environmentally friendly options, and once installed, they cost little or nothing to warm your pool water or to maintain the equipment.

However, solar pool heaters are only efficient in areas with warm climates, because cloudy and cool weather means you won’t be able to heat your pool.

Other Tips For Heating Your Pool

If you don’t want to install an expensive heating mechanism for your pool, here are some cheaper options:

  • Lay a solar blanket over your pool. It prevents evaporation, and since this is how pools lose most of their heat, it will help maintain a warm temperature.
  • Use solar rings. They are similar to solar blankets, cut into circles with magnetic edges automatically connecting to those nearby. They have UV-resistant bubbles on both sides. The lower side is darker to absorb and retain the warmth, while the top provides insulation, preventing heat loss.
  • Use a liquid chemical blanket. It is safe for pool equipment, people, and pets and can increase the water temperature by 6°F.


If you want to extend your swimming season, four types of pool heaters are available: heat pumps, electric heaters, gas heaters, or solar power. The heating systems are incorporated into the pool’s circulation system, where the heat exchange occurs. The system returns the water to the pool, warm and balmy. If you’re a dedicated swimmer, it’s worth taking the plunge and heating your pool.