Obviously, you know that investing in a larger HVAC system will cost you more money up front to buy the system but having a HVAC system that is too large for your home will also cost more money in operating costs, maintenance and repair costs, and ultimately replacement costs.
Short Cycling. It may seem odd that having a smaller, but properly sized, HVAC unit that runs for longer periods of time will use less energy than a system that is larger and doesn’t run consistently, but the reason for this has to do with short-cycling. A unit that is too large for your home will pump out a lot of air in a short period of time, quickly shut off, and then have to turn back on over and over again because the area of your home was not properly cooled. It requires much less energy to keep a smaller unit running consistently to maintain the temperature of your home than it does to have a larger unit start and stop over and over again to go through the cooling cycle repeatedly.
Expensive General Maintenance. Having a HVAC unit that is too large for your home will also cost you significantly more in the maintenance and repair costs, in every aspect, than having a smaller, properly sized unit would cost you. The larger your unit is, the larger and more expensive the air filter it will require is likely to be, and because you will need to change the air filter multiple times throughout the year these costs can really add up quickly.
Expensive Repairs. Additionally, if any repairs need to be made to a larger unit, most of the replacement parts for the unit including fans, motors, and condensers will all be more expensive than they would be for a smaller sized unit. This means if you have a unit that is too large for your home you will consistently be paying more money than you need to in order to maintain and repair the unit.
Excessive Wear and Tear. When you have a larger unit than what you need the short-cycling of the unit causes more wear and tear on the unit, increasing the likelihood of your system wearing down and needing repairs more often. An oversized unit also tends to experience premature failure, meaning you will need to replace the unit sooner than you should need to.