What is a Manual J calculation?

ACCA Manual J is the industry standard for residential load calculations in the United States. It determines the heating and cooling capacity needed for your home based on climate data, construction details, and other factors.

What are ASHRAE design temperatures?

ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) publishes design temperatures for locations across the US. These represent the extreme temperatures your HVAC system should be sized to handle.

How do I know what size AC I need?

AC size is measured in tons (1 ton = 12,000 BTU/h). This calculator determines your cooling load based on your location, home size, insulation, and windows, then recommends an appropriate AC tonnage.

Why is proper HVAC sizing important?

Oversized equipment cycles on and off frequently, wasting energy and reducing comfort. Undersized equipment runs constantly and can't maintain desired temperatures. Proper sizing ensures efficiency, comfort, and equipment longevity.

Heat Load Calculator (US)

Estimate your home heating and cooling requirements based on ACCA Manual J methodology. Get accurate BTU/h calculations for furnace and AC sizing using ASHRAE climate data.

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Where is your home located?

We use your location to determine the design temperatures for your region.

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ACCA Manual J Design Temperatures

Your location determines the outdoor design temperatures used in the calculation. These are based on ASHRAE climate data (99%/1% design conditions).