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How Big of a Pool Heater Do I Need?

Sizing your pool water heater can be complicated. There is an equation which can be used to simplify your pool water heater size and help you decide what way to go.

Pool Gallons x 8.33 x Desired Temperature Rise / 24 hours = required BTU’s.

You will need to keep in mind that a gas water heater will require higher BTU due to the fact of its efficiency. On an average, a pool water heater ranges from 5-90% when its comes to efficiency. Hence, if you calculate, every BTU will reoughly give you a .75 to .90 BTU's of output. A heat pump is quite different, and can potentially provide 3-6 times more heat than the input BTU. If you undersize your pool heater, no matter the type, the result will be slower and lower temperature rise, longer operating time, and shorter seasons.

How Much Heat Will a Pool Heater Add to My Pool?
A huge aspect of choosing your new pool heater is, what you need or expect the heater to do. A temperature rise of 20 degrees may be easily possible in your situation. You can base your decision off of when and how you’re going to be using the pool. If you’re looking to dramatically extend the swimming season, or even to heat your pool or spa year round, a gas heater is going to be the best choice. Although they are usually the most expensive to run, they do not depend on air temperature or sun exposure, which is usually low and in short supply in the colder months. A gas heater will also be your best option if you are more of a ‘weekend warrior’ in regards to pool use, and are looking to quickly raise water temperature.
A heat pump will be able to add up to a few weeks to a few months onto both ends of your swimming season. They rely on drawing warm air, so without that, they become inefficient and usually will not function well below 45-55 degrees Fahrenheit. For economical pool heating, however, and if you are an everyday pool user, a heat pump will be a great fit. Heat pumps heat slowly, and despite the large amperage circuits that run them, they run very efficiently and can operate for $1/day in most cases.

Solar pool heating is going to have the shortest effective range out of the main types of pool heaters. Solar, like heat pumps, must have warm temperatures to be functional. Not only does a solar heater need warmer temperatures than the current water temperature to work. In other words, a 75 degree day with 65 degree pool water would allow the solar heater to make up that 10 degree difference. Conversely, running your solar heater on a 65 degree day with 75 degree pool water would in fact cool the water. Some customers will even take the extra step and use a solar heating system in conjunction with either a gas heater or heat pump. This will give you the extension of the pool season you’ve been looking for with very low operating costs in the warmer months. Each of these heating options will be an outstanding addition to your swimming pool, and depending on the situation will be extremely effective in taking the chill off of the pool.