You know how the old saying goes: “If it’s bigger, it must be better” and “Everything’s bigger in Texas!” While some of us might have an affinity for super-size fries, bigger is definitely not always better when it comes to buying an air conditioning unit. Consider this contestant’s spouse who was featured on the documentary Hands on a Hardbody and who shared what happened when he took a 20-ton air conditioner from a large retail store and placed it in his mobile home:

Suffice it to say that the air conditioner he got on sale was not the right fit for his home and cooled his home too much! While this example is a unusual and a little extreme, purchasing the right size air conditioning and heating system is very important for a number of reasons. Here’s what you need to know:

How does an HVAC contractor determine how large of a unit to install?

The size of a central air conditioner and heater is often measured in tons, and many homes on average may use a unit that distributes 3-tons worth of air conditioning. A large office building or Walmart might use much more. Before your home was built, engineers determined your home’s heat load or how much energy would be required to regulate the indoor temperature. In addition to square footage, they would look at the parts of your home that are shaded by trees or nearby homes, the energy efficiency of doors and windows, the color of your roof, the type of insulation you have, and other design features of your home. From this and what is known about the Houston climate, they would be able to determine how much air conditioning and how large a unit or whether multiple units are needed to properly air condition all areas of your home.

What are the consequences for installing a unit that is too big?

If your unit is too big for your space, the first thing you may notice is that you aren’t as comfortable as you might expect. When your air conditioner starts up, it removes humidity from the air and it cools the air. If the unit is too big, it will cycle off before humidity is removed from the air. This means that it will cool quickly but the air is still sticky.  Long term, this can cause the walls in the home to sweat. This is much the same as what happens when you have a cold glass of ice water by the pool on a hot day. As the ice melts, water condensates on the side of the glass and drips down the side.  This is what can happen behind the walls when a unit is oversized. If this continues to happen it  can lead to a build-up of mold and mildew and adversely affect indoor air quality. At the extreme, it can rot the wood in the home from the inside out.

Don’t I need more A/C, I added on a room?

Maybe you will and maybe you won’t. The only way to definitively tell how much more air conditioning or heating you will need is to get a professional engineer to give you a new heat load that your HVAC contractor will use to sell you the right sized equipment. Normally what happens if there are no substantive changes to the home, an HVAC contractor will install the same size equipment that you had before. If you make changes to your home’s design such as adding a room, energy-efficiency features, etc., then a new heat load calculation may be in order.  If areas of your home aren’t cooling or heating properly it could be that the HVAC system is too small, but it could also be that there is an air distribution problem that can be easily fixed without the purchase of a larger unit.

Let us help you

Looking for reliable advice to cool or heat your home or business? Call Rob and Kenny at Terry’s A/C and Heating at 281-495-7830  in the Southwest Houston, Texas area and surrounding communities of Katy, Stafford, Richmond, Fulshear, Bellaire, Rice Village, Memorial, Meyerland, the Energy Corridor, Sugar Land and more. We don’t work on commission and we will never pressure you into a sale. We know changing HVAC equipment is a long term investment, so it’s important to us that you take your time and consider your options. Find out what our customers say about working with us and what makes us different from other HVAC contractors in the area. We would appreciate the opportunity to earn your business.