Sizing Your Equipment

Use the color-coded map above to find your home’s zone. Then, reference the chart below to match the square footage of your home with your zone. This will help you choose the most efficient unit for your space.

	ZONE 1	ZONE 2	ZONE 3	ZONE 4	ZONE 5
1.5 Tons	600 – 900 sf	600 – 950 sf	600 – 1000 sf	700 – 1050 sf	700 – 1100 sf
2 Tons	901 – 1200 sf	951 – 1250 sf	1001 – 1300 sf	1051 – 1350 sf	1101 – 1400 sf
2.5 Tons	1201 – 1500 sf	1251 – 1550 sf	1301 – 1600 sf	1351 – 1600 sf	1401 – 1650 sf
3 Tons	1501 – 1800 sf	1501 – 1850 sf	1601 – 1900 sf	1601 – 2000 sf	1651 – 2100 sf
3.5 Tons	1801 – 2100 sf	1851 – 2150 sf	1901 – 2200 sf	2001 – 2250 sf	2101 – 2300 sf
4 Tons	2101 – 2400 sf	2151 – 2500 sf	2201 – 2600 sf	2251 – 2700 sf	2301 – 2700 sf
5 Tons	2401 – 3000 sf	2501 – 3100 sf	2601 – 3200 sf	2751 – 3300 sf	2701 – 3300 sf

Proper System Sizing

Choosing the right size central air conditioner for your home involves more than just guesswork—it’s rooted in science. One key approach to determining the correct size is through a Residential Load Calculation, a method that considers factors like your home’s size, number of occupants, insulation, and windows.

Another common way to size an air conditioning system is by checking the size of the unit you already have. While manufacturers don’t explicitly list the system size on the unit, you’ll often find the capacity coded into the model number of the outdoor unit.

Here’s a quick reference to decode the model number and estimate your existing system’s size (make sure to use the system model number, not the serial number):

18 = 1.5 tons
24 = 2 tons
30 = 2.5 tons
36 = 3 tons
42 = 3.5 tons
48 = 4 tons
60 = 5 tons

Why Bigger Isn’t Always Better

One important thing to remember is that bigger isn’t always better when it comes to air conditioners. Installing a unit that’s too large for your space can cause a problem called short cycling. This happens when the compressor shuts off before it runs long enough to properly dehumidify your home.

Short cycling doesn’t just make your home feel less comfortable—it also forces your system to turn on and off more frequently, leading to higher energy costs and unnecessary wear and tear on the unit. Ultimately, this shortens the lifespan of your A/C.

Properly sizing your air conditioner is critical for achieving the best performance and efficiency. Take the time to determine the right fit for your home and enjoy optimized cooling, comfort, and savings.

Heating Square Footage By Climate Zone

This guide will help you determine the heating requirements for your home. Here’s how to use it step-by-step.

30 – 35 Btu’s per square foot

35 – 40 Btu’s per square foot

40 – 45 Btu’s per square foot

45 – 50 Btu’s per square foot

50 – 60 Btu’s per square foot

Step 1: Determine Your Heating Factor

Use the lower number from the table if your home is well-insulated.
Use the higher number if your home is older or poorly insulated.
Not sure about your insulation? Play it safe and use the higher number—you’ll thank yourself later.

Step 2: Find Your Furnace Model Number (Optional)

If you know your furnace model number, you can skip the heating factor calculation. Lookup your model number to find the right match using our furnace model number decoder. If you need assistance, we’re just a phone call away!

Step 3: Multiply Heating Factor by Square Footage

Once you have your heating factor, multiply it by your home’s total heated square footage to find your approximate heating capacity requirement.

Example Calculation

For a home in the yellow zone with adequate insulation:

Heating factor = 40
Total heated square footage = 2,000 sq. ft.
Calculation = 2,000 sq. ft. × 40 = 80,000 BTU actual output

Step 4: Calculate Gas Furnace Output (If Needed)

To assess how much output your gas furnace needs, multiply the efficiency rating by the furnace’s input rating.

Example 1 (80% Efficiency)

Furnace input rating = 100,000 BTU
Efficiency rating = 80% (0.80)
Calculation = 100,000 × 0.80 = 80,000 BTU actual output

Example 2 (93% Efficiency)

Furnace input rating = 100,000 BTU
Efficiency rating = 93% (0.93)
Calculation = 100,000 × 0.93 = 93,000 BTU actual output

For the original example, an 80% efficient furnace with an input rating of 100,000 BTUs will meet the 80,000 BTU heating requirement for a 2,000 sq. ft. home.

Understanding the Variables for Choosing the Right HVAC System

Selecting the perfect air conditioner or furnace for your home involves multiple variables that directly impact the system’s efficiency. Key considerations include your home’s insulation, the type and number of windows, the number of stories, and construction materials. All these factors greatly influence the BTU requirements for both heating and cooling.

Insulation and Windows: If your home is well-insulated and has newer windows, you can typically choose a smaller system matched to your total square footage. However, homes with poor insulation, older windows, or a high number of windows require a larger system to counterbalance the higher levels of air and heat loss.

Home Layout: A two-story home places less strain on the heating and cooling system for the downstairs level because the upper floor offers additional insulation. That said, poorly insulated spaces or homes with many windows often demand additional capacity to maintain comfort effectively.

Sizing a Commercial Packaged Unit AC

Determining the correct size for a commercial air conditioning system is crucial for optimal performance. Whenever possible, it’s advisable to match the size of your current equipment. For new construction or building additions, follow these steps to calculate the ideal size system:

Calculate Square Footage:

Measure the total square footage of the building or area you want to cool, noting that the following method assumes an 8-foot ceiling.

Determine Base BTUs:

Divide the total square footage by 500.
Multiply the result by 12,000 to determine the base BTU requirement.

Add Additional BTUs:

Add 380 BTUs for each person typically occupying the space during working hours.
Add 1,000 BTUs for each window in the area.
Add 1,200 BTUs for each kitchen present.

Calculate Required Tonnage:

After totaling all BTUs, divide the final number by 12,000 to determine the required tonnage for your commercial HVAC system.

By carefully evaluating these variables and performing the necessary calculations, you’ll be well-equipped to choose the ideal HVAC system for your space.

How to Size Your Duct Work Correctly

Proper duct work sizing is essential when upgrading or modifying your system. To make the process easier, we’ve created a simple guide to help you estimate the correct size for your duct work. Keep in mind, this guide serves as a starting point and not a replacement for professional advice. We strongly recommend consulting a technician to inspect your duct work and ensure the sizing is accurate and optimal for your system’s performance.