How Long Does It Take To Heat A Pool With A Propane Heater. Always oversize when purchasing a pool heater. Most current propane heaters won’t even begin working until the air is about 52 to 60 degrees fahrenheit.
Overall, a heat pump usually requires between 24 and 72 hours to heat a swimming pool by 20°f (11°c) and between 45 and 60 minutes to heat a spa by 20°f (11°c). The main obstacle with heating a pool is not the volume of water in the pool, but the amount of heat loss through evaporative cooling that occurs across the service. They also don’t go bad as fast as gas pool heaters do.
So how many hours will the heater run for?
The average propane pool heater burns about 1 gallon of propane per hour per 100,000 btus. This means you can turn on the heater a few hours before hopping into a warm pool. Pool heater costs at a glance. For a typical size 400,000 btu pool heater, that's 4 therms per hour.