The average person thinks that bigger is better. If one is good, then two is excellent. This reasoning does not work in air conditioning sizing. A bigger air conditioner is not better. There are three reasons why:
1) Efficiency – Manufacturers never test their equipment in a home. They will sell you a unit and tell you it gets a certain SEER or efficiency rating, but that rating doesn’t mean anything in your home. They test their equipment in a laboratory. In the laboratory, the unit has to run at a certain state for 15 minutes to get that rating. In your home, the unit may take 20 minutes to achieve that state.
2) Highway Driving vs. City Driving – An oversized unit turns on, turns off, turns on, turns off. Just like city driving is hard on your car because of all of the stops and starts, being too large is hard on your air conditioning unit. Your unit will experience more wear and tear and run down more quickly if it is too big.
3) Dehumidification – When your unit is too big and starting and stopping, it is not properly dehumidifying your home. Your unit really needs to run from 15 to 30 minutes to do its maximum job in dehumidification.
A perfectly sized air conditioning unit would come on around 10:30 in the morning and run until midnight without shutting off. It would keep your thermostat below 80 degrees F – somewhere between 75 and 77 degrees F. You would be perfectly dry and perfectly happy. If you need to set your thermostat lower than that, you are probably not doing a good job at dehumidification, and you’re not comfortable in your home because of that.
If you’d like more information, give us a call! We would be happy to speak with you about air conditioning sizing for your home.