Heat Pump Pool Heater Sizing

A great addition to a backyard pool is a heat pump pool heater. It can make that pool even more inviting on days when the sun is not hot enough to heat the water. Determining what size pump to buy for your pool requires more knowledge than just your pool size.  Do some measuring and find a few answers and you will be armed with the correct information to purchase the right pool heater.

Preferred Pool Temperature

Make a determination of how warm you would like the water. General preference is between 70 and 80 degrees Fahrenheit.

Regional Weather

Do some research with the National Weather Service to get an accurate average local temperature.

Pool Size

Determine the surface area of your pool. Calculate this as you would measure a floor, multiply length by width.


Using the average daily temperature, subtract your preferred water temperature, to determine what degrees your pool heater will need to produce. Multiply this degree with the surface area calculated, multiply this figure by 11, which will give you the BTU’s your heater size will require.

Pools heaters come in predetermined BTU sizes, opt for the one larger than your need. Say you calculate 32,000 BTU requirement and you find pool heaters at 30,000 BTU’s and 50,000 BTU’s opt for the 50,000 BTU’s