Choosing A Pool Heater

An unheated swimming pool can only be used when it is warm enough, so your use of your pool can be increased by installing a pool heater. Pool heaters are available from several different manufacturers and in a range of power levels, which means that choosing the right one for you is not easy.  You also have to decide if you need a gas pool heater, a pool heat pump or whether you location is suitable for a solar pool heater.

Pool heaters come in a range of types and capacities and you need to carefully select the right one for your pool. This is not as easy as it seems as although it is easy to calculate the amount of water to be heated there are other factors to take into account which are harder to quantify.

Heater capacity is quoted in BTUs per hour. For example the Raypak 2100 models range from 206 – 406k BTU and the Hayward H Series ranges from 150-400k but the Hayward H250 seems to be most popular. (One BTU is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit.) A larger heater will be slightly more efficient but, at the same time, it would be pointless to spend more than is needed.

The factors to take into account are:

  • Size of pool – The volume of water in the pool and the surface area.
  • How you will use the pool? – Will you be heating the pool constantly or, for instance, just at weekends? If you are heating the pool intermittently then you will need a larger heater than if you are heating the pool constantly.
  • Temperature increase needed – What temperature do you want the water to be heated to and what is the air temperature in the coldest month you will be heating the pool?
  • How the pool is located – How exposed is the pool to the wind? Wind is a big enemy of heated pools because it increases evaporation and hence heat loss. The pool should be sheltered from the wind if at all possible.
  • Will you use a pool cover? – Pools that are not covered can lose 4° F to 5° F overnight in most locations. Use of a pool cover will reduce that by about 50%.

For an average location an indication of the requirement for a pool heater can be calculated as below:

Area of pool (sq. ft.) X Temperature increase needed in coldest month X 12

Of course this cannot consider the specific factors of location and use of an individual pool. In general you are better off buying a slightly bigger heater than you think you need. It will warm up the water more quickly and with less strain on its mechanics, which should help it last longer.

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