Best for
- Gas-heater shoppers
- Heat-pump shoppers comparing capacity
- Owners deciding whether to upsize
Watch for
- Manufacturer sizing methods differ
- Heat pumps lose capacity in colder air
- Gas line and electrical service can limit equipment choice
Surface area drives heat loss
A large share of pool heat loss occurs at the water surface. Two pools with the same gallons but different surface areas can therefore need different heating capacity to hold temperature.
Define the job before choosing BTUs
Maintaining temperature, heating from cold for weekends and extending the shoulder season are different jobs. A larger heater shortens recovery time but may require larger gas or electrical infrastructure.
A cover changes the economics
Reducing evaporation can materially cut heat loss. If you routinely cover the pool when it is not in use, the heater may need to replace far less lost heat than an uncovered pool in the same weather.
Pool-equipment claims are often based on different pool sizes, operating modes or test conditions. Compare the same job, pool dimensions and ownership assumptions before choosing a product.