Last updated: April 23, 2026
HVAC BTU & tonnage calculator
Pick your SD County climate zone and home profile. Get a calibrated BTU load estimate and AC/heat pump tonnage range, good enough to sanity-check a contractor quote.
Want a real Manual J plus Manual S equipment selection? Call (442) 777-6440. Climate Pros SD matches you with a licensed company that runs those before quoting. We do not install.
Call (442) 777-6440How this works. Baseline BTU-per-sq-ft is a climate-zone rule of thumb for San Diego County, then home age and ceiling height apply multipliers. The result is a sanity-check estimate, not a bid. An actual install quote starts with a full Manual J from the matched licensed company. Climate Pros SD does not publish installed prices from this tool. Confirm live SDG&E offers at sdge.com/rebates.
FAQ
Is this a real Manual J?
No. A full ACCA Manual J calculation factors in window orientation, shading, infiltration rate, duct losses, and dozens of other variables per ACCA HVAC Design Excellence. This calculator is a well-calibrated estimator, good enough to sanity-check a contractor quote, not good enough to order equipment from.
Why do coastal and inland numbers differ so much?
Coastal San Diego averages 68-72°F most days year-round, so the design cooling load is driven by humidity + solar gain more than raw sensible heat. East County and inland hot zones run well above the coastal normals for weeks, which is a pure sensible-heat load and drives BTU requirements up nearly 2x.
Does this work for heat pumps?
Yes, in SD County, a heat pump sized for cooling is often correct for heating too, because heating loads are usually a fraction of cooling loads. Exception: backcountry at elevation (Julian, Pine Valley) where heating loads can rival cooling. The matched licensed company sizes those separately.
Do I need a Manual S equipment selection too?
Yes, if you're actually installing. Manual S takes the Manual J load and matches it to specific equipment (not just tonnage). Climate Pros SD does not publish an installed-price band from this calculator.
What about two-story homes?
This calculator assumes single-story or uniform two-story. True two-zone systems, where you want independent upstairs/downstairs control, need separate load calcs per zone and different equipment selection.
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