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Pool Heater BTU Calculator

BTU output needed from gallons, temperature rise, and heat-up hours, plus the rated size to buy after efficiency.

Inputs

Inputs and assumptions

Gallons to heat, spa included if heated together.

Desired degrees Fahrenheit.

Acceptable heat-up time. Gas 8-24 hrs, heat pump 24-72 hrs.

Gas ~0.8, heat pump COP handled separately.

Result

Heater size needed (BTU/hr)
104,250
Rated size to buy (BTU/hr)
130,313
Sizing estimate from label inputs. Confirm gallons, flow, BTU, and efficiency from manuals before buying equipment.

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Guides

01 Pool Heating Cost Guide (2026)

Related articles

01 Pool Build Budget Guide: Costs and Planning for 2026 02 Pool Pump Runtime Guide: Calculate Turnover and Set Your Schedule 03 Pool Heating Cost Guide (2026)

Workspace

Keep the assumptions with the result.

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