What is the best electric pool heater? The first thing you need to consider is the size of your pool. The more your swimming pool is, the more powerful the heater should be. For example, in order to heat a 500-gallon spa tub, you should buy a 37,000 BTU/h heater. Another important factor to consider is maintenance costs and efficiency. While gas-powered models are cheaper to buy, they are more expensive to run. Whether an electric heater is cost-efficient depends on how much power is consumed by the unit. For this reason, you should opt for energy-efficient models. And finally, choose a heater with a compact design so that it doesn’t take much space. We believe that FibroPool FH055 Electric Heater fits these criteria best.

Electric pool heaters offer efficient and comfortable year-round swimming. The electric heat pump (in-ground) pool heaters function best when air temperatures average 55F. degrees. They can be your best choice when you live in an area that does not experience weather extremes. Many resistance type electric (above ground) pool heater models operate just as efficiently at temps as low as 40F. degrees regardless of weather conditions.

You may conveniently turn your electric pool heater on and off as desired. They generally heat your pool water as fast as gas pool heaters and faster and more consistently than solar or wood heaters. Electric pool heaters and heat pumps require a relatively low initial investment. They are reliable, eco-friendly, and heat quickly.

What You Will Learn from This Guide:

How Do Electric Pool Heaters Work?

Electric pool heaters are simplistically designed and the circulating warming process is the same for above ground as well as in-ground heaters. Each unit contains a heating element (a resistor) and uses electricity to charge it and generate heat energy necessary to warm the water. Source water is pumped into the heating unit. It is heated as it passes through/over the electrically-charged resistor. The warmed water is pumped back into the pool. This process continues until the desired pool temperature is reached.

This process is essentially the same for above ground as well as in-ground pool heaters. However, electric resistance pool heaters rely entirely on electricity, whereas heat pumps conserve electricity by pulling air into its heat exchanger. Heat pump compressors increase the heat, that creates hot gases that warm the water in the condenser. Standard heat pump pool heaters use reciprocal compressors to increase the heat. Higher efficiency heat pump pool heaters tend to use scroll compressors.

Types of Electric Pool Heaters

Electric resistance pool heaters consume less space, are initially low cost, and best-suited for small pools, spas, and hot tubs. They use electricity entirely to pull cold water in, heat the resistor over which the water is warmed, and return the warmed water to your pool. Operating costs can be expensive. Heat pumps are more cost-efficient alternatives.

Water-Source Heat Pumps

A water-source pool heater uses an in-ground geothermal process. Electricity is only used to get and transfer heat from source water, such as your unheated pool water, back into your pool. It does not use electricity to heat the water, which saves on operating costs.

Cold source water is heated as it passes over an evaporator coil inside a condenser. The coil warms Freon gas that passes through a compressor that makes it hot Freon gas. The hot gas passes through a condenser where the pool water enters and exits. The pool water is heated as it passes over the coil and returns into the pool. These heat pumps are extremely efficient in all weather conditions since they do not rely on outside air temperatures. Although operating costs are lower, their initial cost is higher.

Air-Source Heat Pumps

Air-source pool heat pumps only use electricity to pull heat from the air and transfer it to a heat exchanger. The liquid refrigerant is stored in the heat exchanger’s coils and converts from a liquid into gas when heat from the air passes over them. The refrigerant goes through a compressor into the condenser where the pool water is heated. The heated pool water is pumped back into the pool. The main drawback of air-source systems is their reliance on ambient air temperature in order to perform up to maximum efficiency.

What Features of Electric Pool Heaters Are The Most Important?

Electric pool heaters primarily operate using a metal resistor heating element and outside electrical current. Condensers, compressors, internal gases, and coils help each particular heater achieve maximum energy efficiency.

Heating Element

Pool water passes through the heating element, is warmed, and is then pumped back into the pool. The heating element is the most important part of the electric pool heater unit. It is made of an electrically charged nichrome wire resistor and comprises a significant portion of the unit. Since nearly all of the electrical current’s energy sent through this resistor becomes heat, it is important the resistor material sufficiently regulates the flow of the electric current.

Energy Efficiency

Energy efficiency is measured using the international COP (Coefficient of Performance) rating system for heating equipment. That is, for every unit consumed, x units are produced.

Traditional above ground electric resistance pool heaters have a COP of 1.0. That means that 1 unit of heat is provided for each unit of electricity; a 1:1 ratio, or 100% efficiency.

Electric in-ground pool heat pumps (i.e.: air-source) have a COP of 3.0 (300% efficiency). Geothermal water-source heat pumps that get and transfer heat from a consistent, renewable energy source that does not rely on ambient air temperatures may have a COP as high as 5.0 (500% efficiency).

For maximum efficiency, correctly size your pool heater to the pool area you wish to heat.

Adjustability / Control Panel

Your control panel determines the amount of energy your unit uses. A lot of electric current contains a lot of energy. You may decide to modify your electrical panel to reduce the amount of electricity your pool heater/heat pump uses. The control panel also allows you to set your pool’s desired water temperature and mode. The control interface communicates with the sensors and cues the fan motor and compressor when to power on/off.

Installation / Maintenance Requirements

A properly installed and maintained electric pool heater can outlast a gas pool heater. Installation and (annual) maintenance is essential for achieving peak efficiency and should always be performed by a professional knowledgeable in swimming pool electrical equipment. Refer to your Owner’s Manual for your unit’s maintenance schedule.

Advantages and Drawbacks of Electric Pool Heaters

In general, electric pool heaters are eco-friendly, emit zero emissions, are not greatly affected by temperature or weather, conveniently turn on and off, heat quickly and efficiently year-round. Their initial cost, reliability, and versatility are their primary benefits. They are generally less expensive to buy and have installed than gas or solar models. They do not depend on sunlight as do solar pool heaters, or negatively respond to extreme temperatures as gas pool heaters do. Many electric heat pumps also allow you to cool the water as well as warm it.

Electric resistance heaters are compact and have a low initial cost (approx. $2,000 new). They have an estimated 5-10 year life span. Electric convection heat pump pool heaters have greater energy efficiently yield (5.0-6.0 COP) and heat a larger pool area more effectively than their electric resistance pool heater (1.0 COP). Electric heat pump pool heaters also have a longer life span (10-20 yrs.) than electric resistance pool heaters (5-10 years).

Overall electric pool heater energy efficiency can depend on the type of electric pool heater you buy. Electric resistance heaters having lower energy efficiency can incur higher monthly operation costs (approx. $500-$600). Because of this and lower BTU output, electric resistance heaters are recommended as backup heaters or for smaller pools and spas. An electric heat pump’s initial cost is higher (approx. $3,000) but they afford higher BTU output making them better-suited for larger pools.

Review of Hayward CSPAXI11 Electric Spa Heater

The cleanly designed Hayward CSPAXI11 electric spa heater is a compact and efficient, feature-loaded, 11Kw electric pool/spa heater that may be installed either above ground or in-ground. The 304 stainless steel tank, threaded head, and safety sensor electric heating element are protected against corrosion and weather.

The Hayward CSPAXI11 electric pool/spa heater conforms to UL standards for indoor and outdoor use. It is easily installed, maintained, and serviced. Its “service ease” design allows easy access to and adjustment of internal controls. It has a front “On/Off” dial display and controls and “On” indicator light. The safety pressure switch will automatically shut off when it detects a drop in the water pressure, if the pump is turned off, or when the filter is dirty. This electric pool/spa unit’s heating element sensors also automatically shut off when they detect overheating.


This 240V Hayward CSPAXI11 electric pool heater model has all the features and capacity of heaters two times its size. It is recommended for efficient use in smaller above ground or in-ground pools, hot tubs, spas, and water heaters. It heats as fast as more expensive gas pool heaters and faster than solar and wood powered pool heaters.

It comes with a 1-yr. warranty. However, the warranty does not cover damage due to improper maintenance or the results of excessive water hardness, incorrect (pH balance) chemistry, or freezing. Do not use in salt water.

Hayward CSPAXI11 11 Kilowatt Electric Spa Heater

By Legacy Parts & Hardware


Last update on 2022-12-14 / Affiliate links / Images from Amazon Product Advertising API

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Electric pool heaters and heat pumps cleanly and efficiently extend your pool’s swimming season and usefulness. Technologies have increased efficiency and reduced costs, heating pollutants, and NOx emissions as well as conserve energy.

Products with a 5-star rating


Product5 Stars Votes
FibroPool FH120 Above Ground Swimming Pool Heat Pump142(37.7%)
Hayward W3H150FDP Universal H-Series 150,000 BTU Propane Pool and Spa Heater122(32.4%)
Hayward W3HP21404T HeatPro 140,000 BTU Pool Heat Pump113(30%)

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