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Manual J load calculation

Manual J is the Air Conditioning Contractors of America procedure for estimating a home’s heating and cooling load. The result is what a heat pump should be sized to. A unit that is too large short-cycles. A unit that is too small runs continuously and still misses the design temperature. Ductless heads in the wrong rooms have the same problem at the scale of one room.

A serious installer can show the load calculation, the outdoor design temperature they used, and how the capacity at that temperature compares with the load. “We put in what the last house got” is not a load calculation.

This directory has a Manual J field. It is true only when the public source says the installer performed or claimed Manual J. The Mass Save network file, the Efficiency Maine locator, the NYS Clean Heat finder, the TECH Clean California contractor file, and the Minnesota mechanical-bond export do not say that. Every launch listing therefore reads “Manual J: not in source.” An empty badge is not an accusation. It is the absence of a record.

Use the checklist in questions to ask a heat pump installer.

Last reviewed 2026-11-03. Publisher: ElectrifyRadar.