Which is Better? Heater or Heat Pump?

Heaters are considered to be accessory equipment and are items that can be considered for the initial installation of the pool or added on years later, depending upon when you feel you would like to have the convenience of swimming in a warm pool or extending what for many is a short swimming season. A heater can add one to two months onto your swimming season; and for some people who have attached spas, having a heater can extend their spa experience well into the fall season.

The technology of swimming pool heaters has tremendously improved to support energy efficiency requirements, safety and ease of use whereby you can program your preferences for temperature and heated times pretty easily. Gone are the standing pilot lights that go out all the time and the inability to keep a perfect steady temperature throughout your heating season. Most heaters now are equipped with electronic ignitions, thus eliminating the need for standing pilot lights.

Selecting a system, be it a swimming pool heater whose primary source of energy is usually natural gas or propane, or a heat pump which is run using electricity, is dependent on several factors such as geographical location, lifestyle of the pool owner, weather conditions such as temperature, wind and humidity and the expected use by the pool owner: for example, are you using the unit to heat a pool and spa or just a spa? Do you use your pool several times a week or at weekends only?

My first question to a prospective buyer is whether they use their pool mostly on weekends and don't foresee using a heater during the week because of lack of pool use; or do they use their pool on a daily basis whereby they want to keep a steady temperature throughout the week without having to wait to have the water heated?

Simple Mechanics: I could get into heat pumps in depth, but let's keep things basic.

Heat pumps operate by drawing in outside air and converting it to heat. For heat pumps, the higher the air temperature, the more heat they can extract and convert into heated water. They generally need an outside temperature of at least 45 degrees Fahrenheit. For cold weather climates the heat pump was rarely recommended because of the temperature’s effect on efficiency, but technology has caught up and made the heat pump a viable option for all geographical areas with a swimming season.

Heat pumps are rated by BTU output and horsepower (hp). Standard sizes include 3.5 hp/75,000 BTU, 5 hp/100,000 BTU, and 6 hp/125,000 BTU.

Today the heat pump has a higher upfront cost than a pool heater; however, the money you invest up front will pay off over time because a heat pump uses half the amount of gas to get the same BTU’s as a pool heater and about a quarter of the amount of electricity as an electric heater. A BTU is derived from British Thermal Units and will increase from 75000 - 450000 BTU's for gas heaters.

A regular gas heater, be it propane or natural gas, is also sized for the pool in BTU's. The pump circulates the pool water, and the water drawn from the pool passes through the filter to the heater. The gas burns in the heater's combustion chamber, generating heat that transfers to the water which is then returned to the pool.

Gas heaters are most efficient if you are heating the pool water for a short period of time or if you want to heat the water quickly. You will typically get 1 degree rise per hour or less, depending on the pool size and outdoor conditions.

The sizing of your pool heater requires calculations of various items such as pool surface area, outside temperature and desired water temperature as well as wind exposure, night temperatures and humidity levels. Or you can just ask your pool professional for their assistance on selecting the correct size you need.

To determine what your choice will be; a heat pump or gas heater, we go back to the question of lifestyle. I usually say if you are a weekend pool warrior where you use your pool heater for the weekend and don't usually use the pool during the week, a gas heater will serve your needs just fine. You can turn on the heater on Thursday or Friday and your water will be warm for your weekend activities.

If, however, you like to swim in a warm pool and you use the pool throughout the week, a heat pump will be more cost efficient as you can set it on a temperature of 82 degrees F, for example, and it will keep your water at that steady temperature.

The differences in cost on average: as an example using the 82 degree desired water temperature for a pool season in New York from May 1st - Sep. 30 would be approximately $2400 for a gas heater and $1200 for a heat pump based on a 1000 square foot surface area.

The differences in initial outlay can be substantial. You will need to price a gas heater of the proper size and include the installation of the heater, which will include having the gas company install the gas line and hooking the heater up properly as well as doing electrical work if necessary. The heat pump generally will need a little more money spent up front, and you will want to have an electrician look at your current situation to see if you will need to upgrade to a 50 amp service, as required for most heat pumps. In our area, for example, a heat pump will cost approximately $1000 more than a gas heater.

$$ CAUTION: Water chemistry is extremely important when using heaters and heat pumps. Poor water chemistry can be corrosive and can cause havoc with heat exchangers, causing them to leak and add metals to your pool. Be diligent with your water testing; I have seen heat exchangers leak two weeks after installation; and the warranty will not cover replacing the exchanger because it was a water chemistry issue. Even if you have the newer cupro-nickel heat exchanger; take care to keep your water balanced; a heat exchanger can cost almost half as much as a brand new heater!!

SAFETY: If at any time you smell gas, move away from the heater and call your gas company or emergency services and they will advise whether to or how to shut the gas supply off safely. Heaters are one product I feel should be repaired and diagnosed by a professional. Please heed all warnings in your products manual.

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