HVAC Load Calculator - Housecall Pro
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HVAC Load Calculator

Find the correct sized HVAC system for any project with our free and easy-to-use calculator.

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HVAC Load Calculator

This HVAC Load calculator allows you to determine the correct equipment size needed for an area based on the factors that influence the energy needed.

What is an HVAC Load Calculator?

An HVAC load calculator is a tool used to determine the appropriate size and capacity of an HVAC system for a specified structure or space. It uses factors such as square footage, ceiling height, doors and windows occupancy, and local climate conditions. With this information, the calculator can estimate the amount of heating and cooling needed to maintain a comfortable indoor temperature and humidity level. This helps ensure that the selected HVAC system is neither undersized, which could result in inadequate conditions, nor oversized, which could lead to energy inefficiency and higher costs.

What is the difference between an HVAC Load calculation and a Manual J calculation?

The HVAC load calculator offers a simplified approach for estimating heating and cooling needs. The Manual J calculation, developed by the Air Conditioning Contractors of America (ACCA), is a more comprehensive and detailed process that requires additional and more specific data to accurately determine the heating and cooling loads of a space. Some of this data may include the orientation of the structure, shading, and the construction materials, among other factors. While both methods are used to determine if an HVAC system is appropriately sized, the Manual J calculation is a more precise and detailed approach, which is why it is the industry standard for residential HVAC load calculations.

What are the most common sizes of HVAC equipment?


The most common sizes for residential HVAC systems typically range from 1.5 tons to 5 tons, with each ton capable of handling approximately 12,000 BTU/h. This range allows for flexibility in matching the system’s capacity with the specific heating and cooling demands of a space.


Commercial HVAC units, on the other hand, can range much larger, going from as low as 2 tons to over 50 tons for buildings requiring a substantial heating and cooling capacity. The size selected often depends on the methods outlined previously, considering factors such as square footage, insulation, and occupancy load.

What is the formula for calculating HVAC load capacity?

BTU/h = (square footage * ceiling height) + (windows * window factor) + (exterior doors * door factor) + (Occupants * 100)

It’s important to note that this formula serves as a guideline, and detailed calculations like those in the Manual J process would provide a more precise determination of HVAC sizing requirements.