What size heat pump for 21 foot round pool?

To determine the appropriate heat pump size for a 21-foot round pool, consider several factors:

1. Pool Volume: Calculate the approximate water volume of your pool. The calculation for a 21-foot round pool is:

Volume = π × (Pool Radius)² × Pool Depth

Assuming a pool depth of 5 feet:

Volume ≈ 3.14 × (21 ft / 2)² × 5 ft ≈ 1767 cubic feet

2. Climate and Location: The ambient temperature of your region significantly impacts the heat pump's efficiency and required capacity. A mild climate requires less heating power than a colder region.

3. Desired Temperature Increase: Determine the desired temperature increase you want for the pool water. This depends on your personal preference and the season in which you'll use the pool the most.

4. Pool Cover Usage: Using a pool cover when the pool is not in use can significantly reduce heat loss, thus reducing the required heating capacity of the heat pump.

Based on these considerations, generally speaking, a heat pump with a capacity between 18,000 to 22,000 BTUs (British Thermal Units) should be suitable for heating a 21-foot round pool efficiently in temperate climates.

However, it's essential to consult with a pool expert or consult professional heat pump sizing guidelines and tools that consider specific climate data, pool insulation, and other factors for the most accurate heat pump sizing.