Pool Heater Output for a Target Heat-Up Time
The inverse of the pool-heater-btu tile: the heater output needed to warm a pool by a rise in a target time, output = (gallons x 8.34 x rise) / (target_hours x efficiency). Warming a 20,000 gal pool +10 F in 5.2 h at 80% needs a 400,000 Btu/h heater; ask for it in 3 h and it jumps to 695,000 Btu/h. Answers 'what size heater do I need' instead of the time from one heater. Ignores cover/standby losses, so add margin. The equipment ratings govern.
Formula and source
Q_btu = gallons x 8.34 x dT; required_output_btu = Q_btu / (target_hours x eff); the inverse of hours = Q_btu / (output x eff).
The sensible water-heating relation (1 Btu raises 1 lb of water 1 F) solved for the heater output, by name.
Audience
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