Manual J — Residential Load Calculation
Also known as: Manual J load calculationACCA Manual JHVAC load calc
Manual J is the residential load calculation standard published by the Air Conditioning Contractors of America (ACCA). It's what HVAC contractors use to determine the correct heat pump or HVAC system size for a given home — based on square footage, insulation, window count and orientation, climate zone, ductwork condition, and occupant load.
Manual J is the HVAC equivalent of the dwelling load calculation for electrical sizing. Both ensure the equipment is correctly sized for the actual load — not oversized (wastes energy, short-cycles) or undersized (can't meet demand). Any reputable HVAC contractor will do a Manual J before quoting a heat pump install.
Manual J is HVAC contractor territory. We do the dwelling load calculation for electrical sizing on our side. The two calculations inform each other — the HVAC contractor's Manual J output (BTU/hr rating) determines the heat pump model, which determines the electrical load, which we plug into the load calculation to determine whether your panel needs an upgrade.
Met this term in a quote or inspection report?
A free whole-home inspection turns jargon into a written assessment of your actual house — you keep the report either way.