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What is static pressure?

Static pressure refers to the resistance against the flow of air through your system. Greater resistance yields higher pressure. When installing a new unit or diagnosing problems with an existing one, your HVAC technician may measure the static pressure of your system.

For an analogy, think of water flowing through a garden hose. If the end of the hose is open, the water flows out in a gentle stream—it’s under low pressure. But if you put your thumb over the mouth of the hose, partially blocking the opening, then you can make the water spray out a good distance. That’s because of the higher pressure pushing the water out.

The more you block the opening, the further the water sprays. You’re increasing the water pressure inside the hose by creating resistance.

Inside of an HVAC system, resistance increases the static pressure by making it harder for the air to flow. Like taking your blood pressure at the doctor’s office, taking the static pressure of your HVAC system can tell you a lot about the overall health of the system as a whole.

High static pressure leads to problems.

It’s important to check your system for high static pressure and correct it because otherwise you can end up with some very serious problems.

  • Higher energy bills: As stated before, high static pressure makes your system less efficient because it has to work harder to move the air. If your ducts aren’t sealed, high static pressure will make them even leakier, which again wastes energy and raises those energy bills.
  • Blower motor blow-out: Because the blower motor must work harder to move air against the resistance in the system, the motor will wear out faster. That’s not a cheap part to replace!
  • Compressor failure: The compressor is another major component that can be harmed by high static pressure. When the airflow is too low, the system may send liquid refrigerant into the compressor instead of gas. Over time, this damages the compressor and shortens its lifespan.


Ultimately, it’s important for your HVAC technician to measure the static pressure of your system and take steps to correct it if it’s too high. In the long-run, this care can save you money on your energy bills and help your system to be more effective and reliable.