For inground pools less than 20,000 gallons, small gas heaters like the Raypak 206K BTU output are suitable. Pools up to 30,000 gallons should look at the Pentair 300K BTU or higher, and pools over 50,000 gallons should look at the Hayward 500K BTU.
Pool heaters measure their power in BTU (British thermal units). One BTU raises the temperature of one pound of water by one degree Fahrenheit. There are 8.33 pounds of water per gallon. That means that if you have a swimming pool that holds 20,000 gallons, it requires 166,000 BTUs to increase by one degree.
We would recommend at least an 85,000 BTU heat pump for a 20,000 gallon pool. If you would like to extend your swimming season into the late Fall or early Spring or you live in a colder area we would recommend a larger unit like the AquaPro 112,000 BTU or AquaPro 137,000 BTU models.
The pool's surface area divided by three gives you the minimal BTU size recommended for that particular surface area. Continuing the example above with the 15 x 30 pool, after dividing by 3, you get 150. Therefore, the minimum size heater that is recommended for a 15 x 30 pool is 150,000 BTUs.
Pools up to 15,000 gallons should look at the AquaPro 77K BTU or higher, and 20,000 gallon above ground pools should look at models like the TropiCal 115K BTU. Pools in very windy or colder areas, or those that don't use a pool cover should consider installing one size larger.
A pool heater can be undersized: if it cannot replace the heat lost through evaporative cooling, the pool's temperature will fall below the ideal. However, there is no such thing as oversizing a pool heater. The larger the heater's output, the faster it heats the water in the pool, and it will not begin short-cycling.
Calculate the pool surface area in square feet by multiplying the length and the width of your pool. Then, use this formula to figure out the BTUs you'll need your heater to put out: pool area (sq. ft.) x temperature rise x 12.
Generally speaking, the amount of BTUs required to heat pool water will be the same, no matter the size of the heater. But a larger one will work quicker than a smaller heater, especially if you have a large body of water you're warming.
Pool Heater Sizing Calculator and Rules
Subtract the average air temperature from the desired water temperature to get the required temperature rise. For size at 4 BTU's per gallon or 1 BTU per liter of water; to heat water in normal summer conditions when the ambient air temperature is about 70°F in a 24-hour period.
Determine BTUs needed to maintain your pool's temperature
To maintain the temperature, you need about 10 BTUs per hour, per square foot of surface, per degree above the air temperature. That means keeping a pool with a surface area of 300 square feet at 80 °F 60 °F weather would require 60,000 BTU per hour.
It still takes the same amount of energy to heat the hot tub water as it would to heat the pool water, so you wont save any money. The hot tub heaters are probably not powerful enough to heat the pool very well.
Efficiency and Installation
By nature, gas heaters have a greater environmental impact than electric. However, electric takes longer to heat up your pool water and is less efficient in colder temperatures. This is because they rely on outside heat to warm up the pool water.
The Raypak Digital Cupro-Nickel Propane 266k BTU Pool Heater, model 14951, is not the least expensive on our list, but for good reason. As far as pool heaters go, this is the pinnacle. Its 266,000 BTU, propane-fueled, heat production is ideal for most residential above ground or inground pools.
If you want to get as much time as possible out of your pool, however, a heater is a good investment. With a pool heater, you can easily be swimming May through mid-October, giving you a good five months of use out of your pool. That's literally double the amount of time you'd get without one.
No, you shouldn't leave your pool heater running all the time. Not only will it increase your electricity bill, but it will put unnecessary stress on your pool heater. Instead, you should run your pool heater to cycle when necessary during the day. That way, your pool will be warm throughout the day and night.
Water capacity is 4,440 gallons (90%) and it is ready for water in 45 minutes.
Length times width gives the surface area of the pool. Multiplying that by the depth gives the volume in cubic meters. If you'd like to find the pool volume in gallons, multiply your results by 7.5, as there are 7.5 gallons for each cubic foot.
It turns out that Olympic swimming pools have some pretty specific dimensions. They are 50 meters long, 25 meters wide, and 2 meters deep. In terms of volume, when full, these pools hold 2.5 million liters of water or about 660,000 gallons.
It depends on a few things to determine how long it takes a heat pump to heat a pool. However, overall a heat pump generally heats a pool after 24 to 72 hours by 20-degrees Fahrenheit. For smaller pools like a spa pool, the heat pump can heat a pool between 45 and 60 minutes.
12,000 BTU – ~550 sq. ft to ~800 sq. ft.
Overall, an undersized heat pump is better than an oversized one. An undersized heat pump will take longer to change the temperature. But, the unit won't be as loud and will last longer. An oversized heat pump will turn on and off more frequently, which will use more electricity.