A BTU is a measure of the heating or cooling power of an HVAC system. One BTU is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. We offer a wide range of systems from 9,000 BTU for small bedrooms up to 36,000 BTU and beyond for large spaces. Choosing the right BTU size is the most important step in your HVAC Load Calculation. An oversized unit will short cycle, while an undersized unit will never keep you comfortable. You can easily Sort by BTU on our site to find the perfect match for your home. It’s the universal language of climate control. Understanding BTUs helps you make an informed choice for your Multi-Zone or single-zone project.