Size Your Coates Swimming Pool Heater

When a swimming pool is in frequent use, a pool heater to make up heat loss may be all that is needed.
Use the following calculations to properly size the heater:

Swimming Pool Heater Sizing:

• Surface Area of the Pool (sq. ft.) = length x width
• Desired Pool Water Temperature: °F
• Average Outdoor Air Temperature: during months in use
• Temperature Differential: Different between air and pool temperatures during the coldest
month of use (desired pool temp. minus average air temp.)
• KW Required = Pool Surface Area x Temperature Differential x 12
Assumes a heat loss of 12 BTU/hour per square foot per °F of temperature difference
between pool and air. 1KW=3,413 BTU/hour

Spa Heater Sizing:

• When the rate of recovery and the spa heat-up time are important, or when the spa is used
frequently, use the following calculations.
• Capacity of Spa In Gallons = Length x Width x Average Depth x 7.5 (gal./cu. ft.)
-OR- Surface Area x Area Depth x 7.5 (gal./cu. ft.)
• Desired Water Temperature Rise Per Hour: °F
• KW Required = Gallon Capacity x 8.3 lbs./gal.) x Temp. rise °F/hr