Doubtless, you have heard that today's residential HVAC systems are so much more energy-efficient than their counterparts from just a decade ago, so it stands to reason that the bigger the system, the more money you will save in the long run. That is not necessarily the case. While figures such as SEER (seasonal energy efficiency ratio) for air conditioning and AFUE (annual fuel utilization efficiency) definitely play into energy efficiency, HVAC units must be properly sized for your home in order to run at peak efficiency levels. Systems that are too big for your home will waste energy and money, while the same goes for systems that are too small.
HVAC systems that are too large or too small for your home will cycle frequently, meaning they will turn on and turn off a lot, leading to a waste in energy, even if the new system is more efficient than the one you had. A cooling system that is too big cools down the temperature very quickly, but it does not run long enough to remove sufficient moisture from the air. Many people turn down the thermostat to make the air conditioner run longer to remove the moisture, increasing the utility bill.
Yet, how do you know if your HVAC system is properly sized for your home? The answer comes from a residential load calculation. When shopping for a new system, your contractor should perform these calculations based on the square footage of your home. These calculations go beyond square footage, however, as size doesn't tell the entire story. Load J calculations consider factors such as number, size, and placement of rooms; number, size, and placement of windows and doors; types of windows and doors; number and arrangement of floors; and your local climate. The formulas used to make these calculations have been computerized so they are quick and accurate. To ensure that your system operates at peak efficiency, also ask for a Load D calculation. This mathematical formula makes sure that your existing ductwork is sufficient to handle airflow properly.