Help to determine correct heater


Bronze Supporter
Oct 31, 2016
Longview, TX
I am looking to install a heater for my 16'x35' SWG pool. I do not have natural gas or propane, so I believe my options decrease significantly. I live in East TX, and currently we can swim between around April thru early October.

Our goal is to be able to swim year around, so the real question is can a heat pump be sufficient to heat our pool?
Coldest ambient Temp is 25F
Desire temp 85F
18,000 gal, 665 sqft surface area

I've read that heat pumps do not work very well when ambient gets below a certain temperature, and you can only get about 15-20F degree rise from ambient.

Has anyone had any luck using an electric heater? Or maybe had a heat pump and electric heater in conjunction to save on electricity costs?



Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
It is all about BTUs. Unless you can plug into the local power grid you can't get enough heat from house electrical service to heat a pool your size.

It takes 1 BTU to heat 1 lb of water 1 degree. Your 18,000 gallon pool has 150,000 lbs of water. The largest Heat Pumps are around 140,000 BTUs. So the best you can expect is to heat your pool less then 1 degree an hour. In cold weather you can lose more then that heat from the water unless you use a cover on the pool to retain the heat.

Pentair has a Heat Pump Calculator to determine the appropriate size Heat Pump for your location. Pentair seems to do honest calculations based on the physics and efficiencies of each type of pump and energy source. It will give you the feasability of a heat pump across the months.