To my understanding a BTU is unit of energy to raise 1lb of water 1 degree F......But in terms of a heater/pool what is the math to find the time needed to raise the water say 1 degree....Was unable to find it on the net. If my pool drops "t" degrees during a cold week how long will it take with an "xBTU" heater to raise the temperature a "y" amount...This will help me figure cost to heat this water and time. I realize theres an efficiency factor of the heater as well. Anyone know of a chart/calculator??? This will also help me size my gas heater.
As an alternative I've considered a fire burning pool heating system (not in city limits). Anyone know of a source for these?