How Pool Heaters Work: A Breakdown By Type

Kenneth Wilson

Fundamentally, a pool heater warms the temperature of the water in your swimming pool, ensuring you can enjoy a dip throughout the year. But of course, it’s not just as simple as that!

Because there are different ways of heating your swimming pool, you should understand how each system works, so you can make a considered decision about which to install at your property.

Below, we’ve explained in detail how electric, gas, and solar heaters or pumps work, and introduced some advantages and disadvantages of each system. We’ve even included a short review of the prices of installing and maintaining each type of pool heater so that you can opt for the best strategy for your pool.

Let’s begin by looking at the three different pool heater systems commonly installed by US homeowners. (Related: What Size Of Pool Heater Do I Need? (And How To Calculate It))

Different Types of Pool Heater

Typically, you will find three types of heaters that you can install at your home. According to the Department of Energy, the three best ways to heat your pool include:

  1. 1
    Electric Pump Heaters
  2. 2
    Gas Heaters (both propane and natural)
  3. 3
    Solar Pool Heaters

Some people may also use electric resistance heaters, but they’re not overly common and are extremely expensive to maintain, which means they’re not a realistic consideration for most people. The following sections explain how the different types of pool heaters work in practice and how each is potentially advantageous.

Electric Heat Pump: How does it work?

Electric heat pumps don’t generate heat; rather, they utilize a fan that draws in heat from outside that is then channeled into the water. Once warm air from outside enters the system, it circulates through an outer evaporator that contains liquid refrigerant.

At this stage, the condenser coil absorbs heat and transforms the liquid into warm gas, which is then pumped into the compressor. While in the compressor, the warm gas becomes very hot and passes through the heat exchanger condenser. Simultaneously, cold water is pumped from the pool through a filter, and when it arrives in the heat exchanger, the hot gas transfers its heat to the water. The water tends to be heated between 3-5 degrees Fahrenheit before passing out and flowing back to the pool.

To complete the process, the hot gas flows back to the evaporator and through the condenser coil, returning to liquid form before the internal heating method repeats itself for as long as the heater is connected to electricity.

For an electric heat pump to work sufficiently, the outside air temperature needs to be above 50F, so it’s not the ideal solution if you’re looking to heat your pool during the cooler winter months.

Pros and Cons of an Electric Heat Pump


  • Extremely reliable: Electric heaters are reliable for the majority of the year. You don’t need to worry about the availability of sunlight for solar or running out of gas. Providing your pump is connected to electricity, it will warm your pool.
  • Can heat or cool: As well as heating your pool, most electric heat pumps can also cool the temperature of your pool, which is ideal during the height of summer.
  • Cheaper to run than gas: The monthly running costs of an electric heat pump are less than maintaining a gas heater.


  • Time-consuming: It takes longer to heat your pool with an electric heat pump than it does with a gas alternative.
  • Temperature-dependent: Electric pump heaters only work if the outside air is warm enough (above 50F) as they don’t generate heat.

How Much Does an Electric Heat Pump Cost to Install and Maintain?

The average cost of installing an electric heat pump is between $2,500 and $5,000. The unit will cost you between $2,000 and $4,000, while labor for its installation will be between $500 and $1,000. Heat pumps are cheaper to run than gas systems, costing in the region of $120 and $200 per month, which is also considerably more than a solar pool heater.

Gas Heater: How does it work?

The most common way to heat your swimming pool in the US is to use a gas heater. Homeowners tend to use natural gas or propane, depending on whether they’re hooked up to a natural gas line or not.

Once installed, water is pumped from the pool through a filter into the gas heater. By burning gas in the combustion chamber, the heat generated is transferred to the water that flows through before returning to the swimming pool.

Gas pool heaters are characterized by their quick heating time, and they are best used for shorter periods of time, given the heightened operating costs. People who have pools at their holiday homes often utilize gas heaters, owing to the fact they heat the water quickly and on-demand.

Pros and Cons of a Gas Heater


  • The quickest way of heating your pool: Gas heaters tend to heat your pool in a matter of hours, and they’re much faster than both electric and solar-powered heaters and pumps.
  • Work in all temperatures: Regardless of the outside temperature, a gas pool heater can increase the temperature of your pool’s water.
  • Slightly cheaper to install: Although there are still considerable costs associated with installing a gas pool heater, they’re lower than those associated with installing electric or solar systems.


  • Expensive to run: Gas pool heaters are by far the costliest way of heating your pool, and you will need to be prepared for a considerable rise in your monthly energy bills.
  • Not ideal if you’re not connected to gas: Propane gas heaters cost twice as much as those powered by natural gas. If you don’t have a gas line in your property, you should think twice about installing a gas pool heater.

How Much Does a Gas Pool Heater Cost to Install and Maintain?

The average cost of installing a gas pool heater is between $2,000 and $4,000, which is slightly cheaper than both electric and solar-powered systems. The unit will cost between $1,500 and $2,500, while labor for its installation will be in the region of $500 and $1,500. But the biggest drawback to a gas-powered pool heater is the monthly running costs. You can expect to pay between $200 and $400 per month for a natural gas heater, whereas a propane system could cost up to $850.

Solar Pool Heater: How does it work?

A solar pool heater harnesses thermal energy from the sun in order to heat the water in your swimming pool. Solar energy collectors are installed on your roof or at the poolside, and a pump is installed to transport water to the collector, passing through a filter on its way.

Within the collectors, the water is heated by thermal energy from the sun before returning to the pool. Most systems also include a flow control valve that automatically diverts the water to the collectors when the heat of the pool water is lower than that of the water collectors. You can install either glazed or unglazed solar collectors to heat your pool, and your choice is likely to depend on the general climate in your area. Unglazed collectors are popular in warmer climes, whereas glazed collectors are better suited to colder temperatures because they capture solar heat more efficiently.

To sufficiently heat your swimming pool, the surface area of your solar collectors should be between 50% to 100% of the surface area of your pool. For instance, if your swimming pool covers an area of 250 square feet, you should install solar collectors with a surface area of between 125 and 250 square feet to heat your pool.

In addition to solar collectors, a pool solar heating system might also include:

  • Solar pool covers: When you’re not using your pool, concealing it with a translucent solar cover is an excellent way of trapping its heat, preventing evaporation, and heating your pool gently.
  • Solar sun rings: Like pool covers; solar rings can be laid on the surface water of your pool. They absorb solar energy and heat the water below. They’re ideal for smaller pools.

Pros and Cons of a Solar Pool Heater


  • Easy and cheap to maintain: Heating your pool with solar means you don’t have to worry about additional energy bills, and solar systems, in general, require little to no ongoing maintenance.
  • Environmentally friendly: Solar heaters are much better for the environment than both electric and gas pool heaters.
  • Long-lasting: Solar pool heaters will last for 15-20 years.


  • Costly to install: It tends to cost between $3,000 to $4,000 to install a solar pool heater, which is a considerable investment for many homeowners.
  • Reliant on sunlight: The success of your solar pool heater depends on the weather. If you live in an area with limited sunlight, installing a solar pool heater isn’t the best of ideas.

How Much Does a Solar Pool Heater Cost to Install and Maintain?

The average cost of installing a solar pool heater is between $3,000 and $4,000. The unit costs between $2,500 - $3,000, while labor for its installation will set you back between $500 and $1,000. You can expect to pay very little to maintain a solar pool system, with annual costs in the region of $0 and $120 realistic.

The Verdict: How Do Pool Heaters Work?

The short answer is that swimming pool heaters work in different ways. Gas heaters are perhaps the simplest to install and operate, but they’re also the most expensive to maintain. Both electric and solar heaters are more economical and better for the environment, but they depend on optimal weather conditions for their operation and come with higher up-front costs.

The bottom line is that the three pool heating methods introduced throughout are effective ways of increasing the water temperature in your pool, which is their required task. As we've explained in this article, the system you opt for largely depends on your personal preference, circumstances, and available budget.


Kenneth Wilson
September 15, 2021

Kenneth Wilson

Retired contractor. Currently residing in Southwest Florida. Now in semi-retirement, I write and manage this blog focused on helping home owners make savvy decisions when it comes to finding contractors and getting their projects done. I also operate remodeling design service for homeowners.

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