Many pools and spas are not used as often as they can be due to short warm weather seasons and uncomfortably cold pool water. Unless located in a naturally warm, sunny, southern climate, most unheated pools are not used more than 3-4 months during the year. Pool and spa heaters and heat pumps provide warm water and allow longer seasonal or all-year use. In this guide, we’ll talk about different types of pool heaters available, things to consider when shopping, and review the TOP 7 Best Pool Heaters worth buying.
- How Do Pool Heaters Work?
- Different Types of Pool Heaters/Heat Pumps
- What to Look For When Buying a Pool Heater
- TOP 7 Best Pool Heaters - Product Review
Where you live, your climate, your needs, budget, and available energy source help determine what type of pool/spa heater and/or heat pump system works best for you. For example, while solar heaters cost nothing to operate, and can increase your average pool use up to 6-8 months/year, solar collectors take up a lot of space and require unobstructed consistent sun for optimal efficiency. Similarly, electric pool heaters are clean and efficient, but they can add significantly to your utility bill.
Your pool heater is likely the most expensive piece of equipment you buy for your pool. They may be compared according to type, operating as well as initial cost, required installation space/footprint, and efficiency.
Electric pool/spa heaters use a resistor element and electrical current to generate heat to warm your pool water. After it is heated, the water is pumped out of the unit and circulated back into your pool. Electric pool heaters are quite effective, but they require a large amount of electricity, which could become costly. Your electrical panel may also need to be modified to accommodate the additional load.
Electric heat pumps transfer heated water to cooler areas of the pool so the overall heated temp is maintained. The system takes warm outside air into the compressor and compresses the heated refrigerant inside. The hot compressed refrigerant heats the water while cold air is expelled.
Gas pool/spa heaters can heat quickly and maintain your desired pool temperature regardless of weather, temperature, or climate. They operate on natural gas or LP and use your existing pump and heat coils to circulate the water and heat your pool, hot tub, or spa. Your pump circulates pool/spa water through the filter to the heater where gas fuel is burned in the combustion chamber heating copper coils the water passes through and is heated before it is returned to the pool.
Solar pool/spa heaters use energy from the sun, a solar collector, filter, pump, and control valve to heat (or cool) pool/spa water. Your existing pool pump circulates the water through the filter and then through the solar collector where it is heated and returned to the pool. This process may be done at night to cool the pool during peak hot climate months.
Electric Pool Heaters
Electric pool heaters are extremely effective, reliable, clean, and require less space than other types of pool heaters. They are easily installed and operated whenever there is power and effectively operate in any weather. However, your regional cost per kW/Hr of electricity and how many hours a day you intend to run the system may increase your utility bill making your electric pool heater more costly to run than gas or solar unit. For these reasons, electric pool heaters are recommended for smaller pools, hot tubs, spas, or in climates where shorter periods of heating is needed.
Electric Heat Pumps
Electric pool/spa heat pumps do not generate heat. They move heat to where it is most needed to ensure your pool is maintained at a consistently comfortable temperature. Heat pumps are easy to install and use and cost little (50% - 75% less than gas heaters) to operate. They provide a reliable, budget- and environmentally-friendly, efficient means of heating and cooling your pool/spa’s water. Electric heat pumps are a good addition for larger pools. They operate most efficiently when the air temperature is 45+ F. deg. A typical electric heat pump can last up to 20 years.
Gas Pool Heaters
Gas pool/spa heaters are most commonly used because they are efficient in any climate. There is no minimum outdoor temperature restriction since they burn fuel (natural gas or LP) in a combustion chamber. They heat quickly (faster than other types of pool heaters), which makes them especially a good choice for hot tubs, spas, and pools that are not used regularly.
New model gas pool heaters are reliable, energy efficient, and less expensive than heat pumps. They are also more environmentally-friendly than in the past. They may be hardwired to natural gas or propane sources. Professional installation costs may reduce any initial cost savings. Their operating cost is determined by the cost of propane or natural gas. Propane gas typically costs more than natural gas. A typical gas pool heater can last as long as 15 years.
Solar Pool Heaters
Solar pool/spa heaters maximize energy efficiency and environmental friendliness. Initial purchase and installation costs may be higher, but they are affordable to operate and require little maintenance. Only solar panels/collectors, the sun, pump system, and enough space to install the collectors are needed. Solar heaters tend to take longer to heat the water than electric or gas heaters, however. They are less efficient in colder or cloudy weather, so a backup heater may be recommended. A typical solar pool heater can last as long as 20 years (barring no glazing/tempered glass panel breakage).
The Most Powerful Pool Heaters
Gas pool heaters have powerful gas burners that offer the quickest and most efficient means of heating your water. Electric heaters are cleaner, but, depending on the size of your pool, they do not heat your water faster than gas heaters. Electric heaters with more than 200K BTU are more efficient (long-term) than a gas water heater, however. Heat pumps are similar to electric and gas water heaters. Their horsepower (HP) relates to heater BTUs.
The Most Economical and Energy-Saving Pool Heater (Cost & Efficiency)
Solar pool/spa heaters cost the least to operate, although the pump must continually run for the heater system to function properly and keep the pool water warm. This can inflate your utility bill as much as an electric pool heater. Gas pool/spa heater operating costs may also run $300-$500/month depending on the type of fuel (natural gas or LP) you use.
Other factors that affect your overall cost/cost-savings beyond the system’s cost and its efficiency rating include:
- the size of your pool/spa,
- if it is in-ground or above ground,
- if there are existing and available hookups, and
- professional or self-installation.
Highly efficient electric heat pumps cost $50-100/month on average and are commonly installed with heaters.
Although electric heaters and heat pumps are more efficient and cost less to operate annually, they are initially more expensive than gas pool heaters.
If you live in a southern climate that is warm and sunny most of the time, a solar heater/heat pump is an efficient, cost-effective solution. Electric or gas heaters and heat pumps can also effectively maintain pool/spa temperatures in southern climates (i.e.: Texas, Louisiana) for year-round use. A heat pump may be added to extend use a few more months if you live in a southern region that is further north (i.e.: Virginia).
Pool/spa heaters are imperative if you live in northern areas. Natural gas heaters that warm the water quickly are recommended. Electric heaters are initially more expensive but can you’re your water faster. Heat pumps are also recommended to maintain constant comfortable heat and extend pool/spa use in cooler northern climates. You may consider a combination heater/heat pump system.
In Season Water Temperature
You may purchase a pool/spa heater to enhance or improve your pool’s water temperature during the normally hot weather season. Most electric, gas, and solar pool heaters and heat pumps improve your pool’s “in-season” water temperature with little effort. Location makes little difference.
Extending the Swimming Season
Heat pumps move heat from one area to another rather than generating heat, which makes them a good solution for extending your swimming season. However, they work better in warmer climates than colder ones.
Solar pool heat pumps provide cost-free warmth and year-round efficiency in southern climates. They may also extend comfortable pool/spa use (approx. 2-3 months) in northern climates. These are especially effective if the collectors are located facing south, in shade-free areas.
Electric and gas heat pumps also extend pool use by 2-3 months depending on your climate and location. How long electric heat pumps may extend your pool use per year is determined by how long a 55+ F. deg. air temperature exists. How long gas heat pumps may extend your pool use is determined by how long a 50+ F. deg. air temperature exists.
Keeping your pool/spa water warm (conserving your water’s heat) reduces heating costs.
Pool covers and solar blankets made of insulating thermal air bubbles attract sunlight that helps keep the water warm. These insulated covers and blankets can increase your pool/spa’s temperature as much as 10 deg. They are a low-cost way to improve your heater’s efficiency.
Sizing Your Pool/Spa Heater
Decide what temperature you want your pool/spa water to be and calculate the heater size (BTU). Average the outside temperature (include the coldest month) and subtract the average outside temperature from your desired pool/spa water temp to find the “temperature rise”.
Next, calculate the SF pool/spa area (length x width OR radius square x 3.14). Add the temperature rise and total pool/spa SF area and multiply by 12 to get the total BTU you need.
Heat pumps are similar to electric and gas water heaters. Their horsepower (HP) relates to heater BTUs. For example: a 3.5 HP heat pump = 75,000 BTU; a 5HP heat pump = 100,000 BTU, etc.
Pool/Spa Heater Installation & Maintenance
Proper installation and maintenance are required to ensure you gain maximum efficiency and use from your pool/spa heater and/or heat pump. Routine water testing and equipment care are necessary to ensure long-lasting use.
Install your pool heater properly and appropriately to ensure it lasts as long as possible. Pool equipment must be installed in a specific order:
- heater, and
- the salt water chlorinator generation cell.
The pool/spa heater’s metal components rapidly corrode when they are constantly exposed to chlorine. The purpose of the salt chlorinator cell is to allow only fully-diluted pool water to infiltrate the heater casing. If you install it before the heater is installed you risk allowing concentrated chlorine to run directly through the heater system. The concentrated chlorine will damage the heater after only a few weeks (after installation).
Pool/spa heaters most commonly fail ahead of their time due to galvanic corrosion. A bonding wire attached to the heater casing reduces the corrosive effects and the heater’s premature failure. A licensed electrician will install the bonding wire (typ. #6 AWG bare copper ground wire) to the casing lug. The other end is connected to your power service main electrical ground. Alternatively, the ground wire may be run to a grounding plate installed near the pool equipment.
Poor water chemistry contributes to early pool heater failure. Water chemistry involves free chlorine, pH, alkalinity, and calcium hardness that all work together. Water chemistry requires chlorination, periodic chemical shock dosing, and water softeners to balance pool water. Too much or too little chlorine, for example, can be harmful to swimmers. Uncontrolled salt chlorinators and chemical dosing devices can also result in an increased chlorine level that can damage your heater.
Balancing Chemical Levels
It is important to test your pool water regularly to ensure chemical levels are balanced. The quality of your pool/spa water is affected by the pH level, which is affected by alkalinity. High pH levels cloud produce scaly deposits and cloudy water. Conversely, water corrosion and stains are visible signs the pool/spa pH and water chemicals are low. High pool/spa water temperature can initiate increases in your water’s pH, alkalinity, and calcium hardness.
After testing your water,
- Add soda ash (sodium carbonate) to raise/stabilize the pH; Use sodium bisulfate or muriatic acid to lower pool water pH.
- Use baking soda (sodium bicarbonate) to increase total alkalinity; Use dry acid (sodium bisulfate) or muriatic acid to decrease alkalinity.
- Use packaged calcium chloride (per instruction) to increase calcium hardness; To reduce calcium hardness, partly-drain and use a flocculant to collect excess calcium; vacuum and refill the pool with fresh water.
Pool/spa check valves are used to keep water flowing in a single direction and keep it from flowing backward. Pool check valves are usually located in front of the filter pump on the incoming suction pipe. They are most commonly used to keep the heater pump full of water and avoid gravity draining when the pump shuts off.
Zoned Heater Bypass
A zoned bypass installed in your pool/spa plumbing system allows you to divert water around the heater when the pool water is unbalanced and cannot safely circulate in your pool/spa heater. A zoned bypass essentially allows you to take your pool heater “offline” so you can adjust water chemistry conditions.
The heat created inside the pool heater unit as well as open accesses attract rodents (i.e.: rats, squirrels, mice, etc.) that can seriously damage your heater and wiring. Be sure your pool heater’s power is completely turned off so no heat from an energized heater circuit exists. It is also recommended to plug access(es) to the inside of the pool/spa heater with steel wool. Spray exposed wires with WD-40 to repel the rodents and prevent wires from being chewed.
Winterizing your pool is necessary to ensure your plumbing, equipment, water, and surfaces are not damaged, slimed, or contaminated when you decide to use the pool next season. You may successfully choose to leave your pool/spa filled and uncovered if you live in a “mild climate.” Continue running your filtration system, clean the filter, vacuum debris, and regularly add sanitizer during the offseason.
If you partially drain your pool during the offseason, clean the walls and filter and vacuum debris. Completely drain water from the pump, heater, pipes, etc. and add pool antifreeze to prevent winter freezing. Add a non-chlorine shock oxidizer and algaecide to help prevent algae growth. A sequestering agent will help protect metal parts and equipment and prevent calcium stains.
Flow Rate Calibration
Your pool/spa heater must be accurately calibrated to ensure its optimal flow rate is maintained. The more accurate the flow rate calibration is, the more efficient your pool heater will be. Use a variable speed pump or zone valve to calibrate the flow rate. Use the pool heater system’s flow meter to monitors the flow rate.
We’ve chosen only the TOP models of different types of pool heaters and described them below. Here, you’ll find gas and electric pool and spa heaters, as well as best heat pumps. At the end of the Product Review section, we’ve included a polymer solar blanket to keep the water in your pool pleasantly warm throughout the season.
Sta-Rite SR333LP Max-E-Therm Propane Gas Pool and Spa Heater
This heavy-duty Sta-Rite SR333LP Max-E-Therm indoor/outdoor pool/spa heater is a compact propane model that exceeds DOE low-NOx emissions standards. It incorporates PMG burner technology that alleviates the need for an outdoor draft hood. It also heats quickly and ranks No. 1 in LP gas pool heater energy efficiency (84%). Its housing is all-weather, rust-resistant Dura Glas thermoplastic resin. The durable heat exchanger can sustain years of use and resists water chemistry imbalances.
The Max-E-Therm pool heater features top-mounted dual thermostat controls, a six-position control panel, LED temp and system readout, and lockout. PVC connectors attach directly to a Sta-Rite-brand 3 Mod Media or other system filter making this pool heater universally useful for retrofit as well as custom installation.
This economical 333,000 BTU propane pool/spa heater is intended for residential retrofit or custom installations only. It must be hardwired and installed by a certified professional. A 60-day, parts only warranty is included. Extended 1-yr. warranties are offered.
Sta-Rite: Check the current price
Pentair 460775 MasterTemp Pool Heater, Natural Gas, 400,000 BTU, ASME
The ultra-compact pool/spa heater is a mobile natural gas model that is ideal for those that need to transport, repair, and replace pool heaters. The sidewall ventilation also helps it to fit into areas as small as 2’ x 2’. It surpasses DOE’s low-NOx emissions standards. This natural gas pool heater operates at 83%-84% efficiency. It also incorporates Versa Flo integrated bypass technology that offers auto actuation and on-call heat. The water can flow through the system without entering the heater, which also increases energy efficiency. The blower-driven, copper-tubed heat exchanger has a hot-surface igniter start-up that guarantees easy start-up.
The central feature is its flexible, quick-connect installation that readily accommodates Max-E-Therm (and other) retrofits. A Versa Plumb sweep elbow reduces the need for any plumbing alterations. It also has a dual thermostat control and six-position control panel with LED readout.
Pentair: Check the current price
Hayward CSPAXI11 11Kw Electric Spa Heater
The Hayward CSPAXI11 compact, electric, indoor/outdoor pool/spa heater is an upgraded version of the already-reliable C-SPA-X1 model. It may be used on fountains, water heaters, and hot tubs as well as for pools/spas. This 11Kw unit operates on 240v. It has all the amenities and features its larger competitors offer while still being able to fit into tight areas (i.e.: under decks, in spa sheds, etc.). Its tank and threaded head are durable 304 stainless steel construction. It also has a heating element sensor for safety.
This streamlined pool/spa heater is easy to install and maintain. Easy-dial On/Off controls (with indicator light) and temperature adjustment are easily accessible on the front of the unit. Internal controls are also easily accessible for maintenance and troubleshooting. CSPAXI11 electric pool/spa heater installation must be performed by a licensed professional and include a bonded and grounded 60amp breaker. An external bypass must also be installed if this will serve a spa/hot tub that exceeds 70 gal./min.
This simple, indoor/outdoor electric pool/spa heater upgrade is well-suited for spas (less than 1,000 gal.), fountains, water heaters, and small, low-temperature pools (less than 5,000 gal.). It installs quickly and can be stored in small, concealed areas. A 1-yr. limited manufacturer’s warranty is included.
Hayward CSPAXI11: Check the current price
Hayward HP50TA 50,000 BTU Heat Pro Heat Pump
The Hayward HP50TA HeatPro heat pump is a heavy-duty, compact round-design. Its anti-corrosion construction includes stainless steel, poly-screen, “Ultra Gold”, and injection molded, UV-resilient processes and hardware. Reliability and efficient operation and performance are assured even in the most extreme environments. The HeatPro titanium counterflow heat exchanger also resists deterioration caused by saltwater/coastal conditions.
The HP50TA heat pump is an independent lab (AHRI) certified. It is easily installed on new or existing pools/spas using 2”x2½” CPVC common union connectors that also adapt to larger plumbing. Installation must be performed by a licensed and certified NEC and CEC professional. It has durable electronic controls and scroll compressors, a profiled-fan blade, and cover to promote super-quiet operation.
This durable, lightweight heat pump is designed for new and after-market pool/spa installation. Its overall corrosion- and UV-resistant construction makes it well-suited for installation in above/below ground saltwater pools as well as in unforgiving (coastal, chemical) environments A 1-yr. parts and labor warranty and 2-yr. limited compressor warranty are included.
Hayward HP50TA: Check the current price
Hayward H150FDN Universal H-Series 150K BTU Natural Gas Pool and Spa Heater
The lightweight, low-profile Hayward Universal H-Series pool/spa heater is a rust-resistant, rapid-heat, natural gas millivolt model. Its (patented) polymer-header hydraulic design reduces erosion and pump runtime by 18%. It also incorporates forced-draft combustion that ensures constant air circulation for efficient operation regardless of weather/wind conditions. The H150FD’s cupro nickel heat exchanger, silicon-nitride hot-surface igniter, insulted combustion chamber, and stainless burner provides a durable, anti-corrosive, reliable heater.
The H150FDN pool/spa heater requires 110v./220v. power. It features convenient install/service front panel access and flexible left/right gas/water and 2”x2½” CPVC common union connections. It also has an LED digital control readout panel. Installation and servicing must be performed by a certified technician.
This newly-designed,150,000 BTU natural gas pool/spa heater’s advanced technology and universal flexibility makes it well-suited for new or upgrade/repair residential (only) pool/spa installations. It meets CA and TX low NOx emissions standard and a 1-yr. limited warranty is included.
Hayward H150FDN: Check the current price
Hayward HP21404T Heat Pro 140K BTU Heat Pump
The Hayward HP21404T HeatPro heat pump is a larger, more powerful, super-quiet, square-design of the compact, but no less heavy-duty 50K BTU HP50TA HeatPro model. The HP21404T’s construction also incorporates stainless hardware, injection molded, UV-resilient, poly-screen, and “Ultra Gold” processes and body to prevent inefficiency, deterioration, and extreme environmental damage. The HP21404T titanium counterflow heat exchanger maximizes heat transfer and also withstands harsh saltwater/coastal conditions.
The HP21404T heat pump requires 220v./240v. power. It is easily installed on new or existing pools/spas or systems. It has durable electronic controls. Its scroll compressors and compressor cover provide ultra-quiet operation. This heat pump carries the CA Proposition 65 warning.
This larger, more powerful, lightweight Hayward HeatPro heat pump model is equally suitable for new and existing above/below ground pools and spas due to its resilient anti-UV and anti-rust construction. A 1-yr. parts and labor warranty and 2-yr. limited compressor warranty are included.
Hayward HP21404T: Check the current price
Blue Wave 12Mil Solar Blanket
The Blue Wave 12mil solar blanket is a durable pool cover that is UV-resistant for longer-lasting performance, even in direct sunlight! Innovative technology uses thermal air bubbles that naturally trap heat from the sun and retain it. It is available in sizes from 12’ x 20’ x 0.5” to 30’ x 50’ x 0.5-in. This Blue Wave polymer solar blanket can raise your pool’s swimming temperature as much as 15 F. deg. and heats to the water’s depth. It will help extend your seasonal pool use through cool nights and cloudy days.
The Blue Wave rectangular UV-resistant pool/spa solar blanket is advertised to perform better than Intex pool covers. It is intended for in-ground pools. Install with the bubble side down and clean with soap and water. A 5-yr. manufacturer’s warranty is included.
Blue Wave: Check the current price
Comparative Chart of Pool Heaters
|Type: Propane |
Connection: Hardwire; Universal Direct-Connect
Best For: Indoor/Outdoor Pools, Spas
|Type: Natural Gas |
Connection: Flexible; Headers rotate 180 deg.
Best For: Mobile Pool/Spa Repair/Replacement
|Type: Electric |
Efficiency: Not listed
Best For: In-Ground/Above-Ground Pools, Spas, Water Heaters
|Type: Electric (Heat Pump) |
Connection: Hardwired (Professional install)
Efficiency: Not listed
Best For: Above-Ground Pools
|Type: Natural Gas |
Connection: Hardwired (Professional install)
Best For: New/Existing Systems; In-Ground/Above-Ground Pools, Spas
|Type: Electric |
Connection: Hardwired (Professional install)
Efficiency: Not listed
Best For: In-Ground Pools, Spas
Blue Wave 12Mil Solar Blanket
|Type: Solar; Plastic Sheet |
Efficiency: Increases Pool Temp (+15F. deg.)
Best For: Rectangular In-Ground Pools
Can I install a pool heater myself?
Electric and gas pool/spa heaters and heat pumps require professional installation by NEC and CEC certified technicians/electricians. Flexible (cheaper unglazed) solar panel heater options DIY kits are available and do not require professional installation.
Can it be installed under a deck?
Compact electric pool/spa heaters can fit under a deck. Gas heaters are not recommended due to venting issues that tend to let exhaust gasses seep up through the deck boards making deck users sick.
Are these devices efficient?
Efficiency is based on the heater’s usable output to energy input.
Are pool heaters environmentally-friendly?
Pool heaters that are environmentally-friendly are energy-efficient and have low NOx emissions, corrosion-resistant parts, and a “light carbon footprint.”
Is it noisy?
Noise levels vary w/the manufacturer. The compressor and fan’s motor and blades generate noise levels and pitches.
How much propane does it use?
That depends on the size of the gas pool heater.
Can a gas device be converted to propane?
Consult the manufacturer to ensure your gas pool heater can be converted to propane. Manufacturers sell conversion kits to convert your model to propane.
How much does the maintenance cost?
The cost for a tune-up depends on the type of model and your location. (Average cost: $120).
Where can I find and compare current electric energy rates and pool heating options?
Your local power company can tell you the cost/kWh of electricity or cost for natural gas. LP rates are available from your local LP dealer. You may calculate your heater energy use based on its size and apply local cost for electricity or natural gas/LP. Solar offers “free” energy although you must still run your pool pump. Google “compare pool heaters” for type/brand comparisons.
Can a pool heater freeze?
Yes. Prevent it from freezing by properly winterizing it.
Can a heater overheat and/or explode?
Gas devices must be properly vented to avoid overheating/exploding.
Can it be repaired?
Yes. There are numerous YouTube videos on pool heater repair and maintenance. Also, contact your local repair/maintenance vendors.
Can you leave a pool heater on overnight?
Your device may have a timer or max. temp shut off so it doesn’t overheat. Energy rates are typically lower if you choose to heat your pool at night rather than during the day.
How do you winterize a pool heater?
If the pool remains filled and uncovered, keep the filtration system running, clean the filter, wash walls and vacuum debris, and regularly add sanitizer. A partially-drained pool requires blowing pipes free of water, adding pool antifreeze, and a non-chlorine shock oxidizer.
How do you clean a pool heater heat exchanger?
Test and maintain/balance your water chemistry to prevent heat exchanger (copper) damage.
What is a pressure switch?
It maintains the pressure and the flow in the pump line to move the water through the heater.
What is a millivolt heater?
A pilot light-ignited gas pool heater.
Electric, gas, and solar pool/spa heaters are designed to efficiently raise pool/spa temperatures. Many allow you to extend your swimming season regardless of your climate or location. Electric heat pumps enhance pool heaters by moving the warmed water to cooler areas of the pool to achieve uniform comfort. They may be used with pool heaters for enhanced efficiency.
Energy requirements have motivated technological advancements in efficiency, emissions, and footprint. Today, most natural gas heaters have electronic rather than pilot light ignitions. Other improvements include low-NOx emissions, fan-assisted combustion, corrosion-resistant heat exchangers, LCD display screens, and “state-of-the-art components”.