Understand BTU and Its Effect on Your AC’s Performance

BTUThe BTU, short for British Thermal Unit, is the standard for measuring units of heat. It’s an important specification, because moving heat is an air conditioner’s main function. It extracts heat energy inside your home and moves it outdoors, where it’s dispersed into the air. What’s left behind is a cool, comfortable house.

The BTU specification represents the amount of heat an AC can move in an hour.  It’s usually expressed in tons (one ton equals 12,000 BTUs of heat). Most residential air conditioners are rated from 1.5 tons to 5 tons (from 18,000 to 60,000 BTUs), with the exact capacity depending on square footage of the home and other additional factors like sun exposure, insulation, and number of windows. A qualified HVAC contractor can perform a sizing survey, then utilize industry-standard software to calculate the proper cooling capacity in BTU tons.

Why Accurate Sizing Is Critical

Guesswork or “rule of thumb” sizing isn’t accurate enough to meet today’s standards for energy efficiency and cooling performance. In fact, air conditioners that are too small or too large are both generally unsatisfactory when it comes to monthly operating costs and indoor comfort.

There’s no fix for an undersized or oversized AC. Once it’s installed, you’re stuck with the consequences until a new unit replaces it. Here’s what’s wrong with both too small and too large BTU capacity:

  • An air conditioner with BTU capacity that’s too small for the house won’t cool adequately. What’s worse, it will run extended cooling cycles, sometimes running nearly nonstop, which wastes energy and increases cooling costs while indoor comfort remains substandard.
  • When BTU capacity exceeds home requirements, the air conditioner “short cycles,” turning on and off rapidly before the house is ever uniformly cooled to the proper temperature. Short cycling also impedes the air conditioner’s dehumidifying function, so indoor humidity rises and the house feels clammy. Wear and tear caused by short cycling also takes its toll on critical components like the compressor.

Talk to the pros at Paitson Bros. for more about how air conditioner BTUs impact home cooling and operating costs. We’ve been your go-to source for reliable HVAC information for 100 years.

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