How to Calculate Heat Load

winter is cold so know your heat load

An important aspect to properly planning a central air installation is the inclusion of a BTU calculation to ensure that your HVAC system can adequately heat and cool your home or office. Before we explain how to calculate heat load, we must answer an important question:

What is Heat Load?

Obviously the climate outside has an impact on the temperatures we experience indoors. In extreme climates, HVAC systems must work hard to maintain a comfortable environment. The “heat load” describes the quantity of cooling or heating required for a desirable in-home temperature.

Estimating Your Heat Load Calculation

For an accurate measurement, we recommend contacting an HVAC professional, because there are a variety of factors that can come into play.  These factors include insulation, building materials, number of windows, size and positioning of windows, appliances, electronics (computers, printers, etc. all put-off heat), how many people tend to occupy the home, and more. Heat load is measured in BTUs (British thermal units). One BTU is approximately 1055 joules and is defined by the amount of energy required for heating or cooling a single pound of water by one degree. Here is a simple to use formula. It is not intended to be the standard of truth, but it will definitely give you an idea of what direction to take in planning your HVAC system:

Heat Load Calculation Formula

  1. Take the square footage of your home
  2. Multiply that by the average ceiling height in your home
  3. Multiplied by the difference in temperature desired and the temperature outside
  4. Times a multiplier that represents that the target building is a sealed structure (.135)
hot sun peeking out from behind clouds

In order to illustrate the point further, here is a sample calculation: if you face 30-degree temperatures in your region and you want it to be 70 degrees in a 3,000 sq foot home with 8-foot ceilings, your calculation would look like this: 3000 x 8 x 40 x .135 = 129,600 BTUs Keep in mind that this is a very conservative estimate, meaning you probably will not need an HVAC system that puts out 129K BTUs. When you calculate heat load rather than turning to a professional you will get a less exact number. For reference sake, it seems that professional calculations tend to be in a range between 65-80% of what is calculated by the above formula. Example: a professional will likely find this home to require between 80,000-100,000 BTUs. As the saying goes, it is better to err on the side of caution. As mentioned, for proper planning we urge you to get a professional measurement of your heat load.

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Remember that if you need to replace any component of your system, PlumbersStock has great prices on a huge selection of HVAC parts. If you have trouble finding what you need, please contact us. Don't forget to update your HVAC tools. If you still don't quite understand how to calculate heat load, go ahead and contact us. Whether you heat your home with a boiler, a furnace, or just a space heater, we have you covered.

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