What Size Air Conditioner Do I Need? | Day & Night

Are you looking for a new air conditioner for your new build or did your old HVAC system finally give up on you? One of the first things to consider when installing a new HVAC system is the size of air conditioner you’ll need to stay comfortable all year long. We’ve put together a guide for homeowners to help choose the best size air conditioner for your home.

Factors That Affect the Size Air Conditioner You Need

There are multiple factors that affect the size air conditioner you’ll need in your home, including:
• Ceiling height
• Insulation
• Home size

Why Does Size Matter?

Times have changed. Back in the 1980s, electricity wasn’t as expensive, and homeowners often had large air conditioners. However, HVAC systems these days are built for efficiency. While older HVAC systems focused on bringing the temperature down in a home rapidly, modern HVAC systems work in cycles to steadily bring the temperature down.

If the air conditioning system is too big for your home, it will cost you more in utility bills. This increase in cost is because the HVAC system will turn on and off constantly instead of running a full cycle since it can cool the home so fast.

If the air conditioning system is too small for your home, it will also cost you more in utility bills. Small HVAC systems will run constantly because they’re not sufficient to cool your home properly.

How to Calculate the Best Air Conditioner Size For Your Home

There are a couple of different ways to calculate the best air conditioner size for your home. The first method is an old equation which is house square footage times thirty, divided by twelve thousand, and then minus 1. For example, a 2,000 square foot average American house would be calculated as follows:
1. 2,000 x 30 = 60,000
2. 60,000/12,000 = 5.00
3. 5.00-1.00= 4.00
According to this calculation, for an average American 2,000-square foot home, you would need a 4-ton sized air conditioning unit. However, keep in mind that this is for the average American home, and this calculation doesn’t capture the need for a higher-powered HVAC system for homes in arid or hot climates, such as right here in Arizona.

Another method for calculating the best air conditioner size for your home involves the consideration of more factors than just the home’s square footage. Consult an air conditioning sizing graph to get a general idea of what size air conditioner you need. Air conditioning sizing graphs typically show the different climate zones of the United States along with recommendations for the size air conditioner you need depending on your home’s square footage.

However, the best way to determine the right air conditioning size is to run a “Manual-J” calculation. This method is used by air conditioning contractors to determine the right air conditioning size for your home.

Whole House Load Calculation

A whole house load calculation is a form of the “Manual-J” calculation that determines the amount of cooling needed for the home as a whole. This calculation takes heat transfer between walls, the number of windows and their efficiency ratings, the type of insulation installed, heat transfer through the foundation, lighting, and ducting.

Room-By-Room Load Calculation

A room-by-room load calculation is essentially the same as a whole house load calculation, except it is performed for each individual room in the house and then added together to get the whole house calculation.

When Should I Use a Whole House Load Calculation and When Should I Use a Room-By-Room Load Calculation?

While both calculations have their uses in different situations, it’s generally useful to use the whole-house calculation if you are only replacing your HVAC system. However, if you’re replacing both the HVAC system and your ducting system, you should use the room-by-room calculation. An experienced HVAC contractor can also help you decide which size air conditioner will work best in your home.

Additional Tips for Determining the Right Size Air Conditioner For Your Home

1. Ask your contractor to perform a Manual-J calculation for your home. Just because your old unit was a certain tonnage, this doesn’t mean that you’ll be replacing that unit with the same tonnage. For the best efficiency and the most savings on utility bills, make sure to have the Manual-J calculation performed before picking and installing a new HVAC system.
2. Get multiple estimates. This advice works well for any project completed on your home. You’ll definitely want to get multiple estimates from different contractors.
3. Consider replacing the ductwork. If your ducts are improperly installed or work inefficiently, you will save more money in the long run by replacing the old ductwork.

The Next Steps

After you determine the right size air conditioning unit for your home, it’s then time to consider SEER ratings of possible HVAC systems. SEER stands for Seasonal Energy Efficiency Ratio, and the higher the rating, the more efficient the HVAC units. State legislation usually regulates the minimum SEER rating that is acceptable for newly installed HVAC units, so be sure to follow those guidelines.

How Can Day and Night Air Help?

With decades of combined experience distributed amongst its staff of highly-trained HVAC contractors, Day and Night Air can help you determine what the smallest size air conditioner you’ll need for your home to keep it cool all year long. Call today for an estimate and to talk to an expert!

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