Want to know how long it will take to heat your pool in the winter season? Well, this is a question many people want to know, it is simple and complex as there are few variables to consider. The simple answer is to plug and play with this basic formula. Gallons of water (GW) multiplied by the weight per gallon (8.33lbs) multiplied by the degrees desired divided by the BTU output you have purchased for your pool. For example, a 15,000-gallon pool heated 20 degrees with a heater output of 3,36,0...