If your air conditioner is too big, you are paying for a unit size you do not need. If your air conditioner is too small, your unit will be overworked, and your home may not reach the comfortable temperature you want. You can use our AC unit size calculator below to find the right size for your home. We also explain BTUs and everything else you need to know to pick an AC unit.
AC Unit Size Calculator
Ready to find out what BTU measurement your air conditioner should have? Select your home’s climate zone on the map above to get started using the AC tonnage calculator.
Once you learn what size AC unit your home needs, we recommend connecting with a local HVAC contractor to learn about costs for installation.
What Size AC Do I Need for a 2,000 sq. ft. Home?
While your answer will ultimately depend on where you live and how old your windows and insulation are, you can start by assuming you need an AC unit size of 40,000 BTU or approx. 3.5 tons.
If your home is newer or you have recently replaced the majority of your windows, you may be able to go down as low as 35,000 BTUs/3 tons.
If your home or windows are older than 15 years and/or you live in an especially hot climate, you may need to go up as many as 53,500 BTUs/4.5 tons.
You can use our AC size calculator above to find out what’s right for you.
What Are BTUs for Air Conditioners?
BTU stands for British Thermal Unit. It is a unit of energy used to measure the heating and cooling capacity of HVAC systems. One BTU unit is equivalent to the amount of energy needed to raise/lower the temperature of one pound of water by one degree Fahrenheit.
So, what does all that mean for you?
Well, simply put, if you have a bigger home, you will need an AC unit (or heater) with more BTUs. If you have a smaller home, you won’t need such a large BTU capacity.
What Is the Difference Between BTUs and Tons for AC?
Many air conditioners are measured in tons. As you are shopping for an AC unit, you might see a unit described as a 5 ton air conditioner, but it has no BTUs listed at all.
Tonnage begins at 1.5 tons and increases in .5 ton increments up to 5 tons. A 60,000 BTU unit would be equal to 5 tons, which, as we noted above, is the largest residential air conditioner available.
If you are doing your own calculations and land between tons, size up to the nearest half or whole.
Having a system that is slightly too large will not add much to your cost but will absolutely ensure your home stays cool. Rounding down may mean your unit is overworked, which decreases the lifespan of your air conditioner.
Why Does AC Size Matter?
The size of an AC unit directly impacts its cooling capacity. A correctly sized AC can effectively cool a room or space to a comfortable temperature, ensuring optimal comfort for occupants. An undersized AC will struggle to cool the area adequately, resulting in insufficient cooling and discomfort. Conversely, an oversized AC may cool the space too quickly, leading to frequent on-off cycles, poor humidity control, and uneven cooling.
AC size also affects energy efficiency. When your unit is the right size, it uses just the right amount of energy to cool your home effectively. Units that are not the right size may consume more energy than necessary, leading to higher energy bills.
We created the table below so you can get a general sense of what size air conditioner you may need for a variety of home sizes.
| Home Size | Central AC Size - BTUs | Central AC Size - Tons |
|---|---|---|
| 1,200 | 18,000 - 24,000 | 1.5 - 2 tons |
| 1,200 - 1,500 | 24,000 | 2 tons |
| 1,500 - 1,800 | 30,000 | 2.5 tons |
| 1,800 - 2,500 | 30,000 - 36,000 | 2.5 - 3 tons |
| 2,500 - 3,500 | 42,000 - 48,000 | 3.5 - 4 tons |
How to Calculate BTU Per Square Foot for Air Conditioners
A good general rule to start with for finding the right size AC unit is to have 20 BTU for every square foot of house. So a 1,000 square foot home would need a 20,000 BTU air conditioner. Remember, you can then convert this to tons. 12,000 BTUs are equivalent to one ton.
However, a few other factors can influence how many BTUs you need:
- Do you live somewhere with extreme temperatures?
- Does your home have older insulation?
- Does your home have older windows?
Do I Need One AC Unit or Two?
Did the AC size calculator above recommend more than one unit for your home?
The largest residential air conditioning units typically have a capacity of 60,000 BTUs. But based on your home’s square footage, age, and where you live, you may need more capacity than that. In that case, you need multiple AC units.
Multiple units may be split up by floors. So you might, for instance, have a unit for the upstairs and a unit for the downstairs.
If your home has roughly the same square footage downstairs as upstairs, you can look for two units of the same size. If one floor is notably smaller than the other, then choose a larger size unit for the floor with more square footage and a smaller size unit for the floor with less square footage.
What Are SEER Ratings for Air Conditioners?
SEER stands for Seasonal Energy Efficiency Ratio. It’s a rating system used to measure how energy efficient an air conditioner is.
The higher the SEER rating, the more efficient your AC is. Higher SEER ratings then translate into lower utility bills.
In the U.S., all air conditioners must have a SEER rating of at least 14.
A SEER rating of 16 or higher is considered very efficient. It is a good choice for those concerned about energy costs. However, keep in mind that a higher SEER rating tends to mean a more expensive system. On the other hand, that higher investment up front means lower monthly bills, so you will eventually earn back the money you spent.
Wondering what you can expect a new AC unit to cost? Click below to use our cost calculator.
Why Your Home’s Age and Number of Windows Matters When Choosing an AC Size
The more energy-efficient your home already is, the less BTU capacity your air conditioner will need. If you got a higher BTU number than you expected when you used our AC size calculator, energy-efficiency of your home is probably why. Here’s what to consider.
Your Home’s Age
Older homes have older materials in them. That means not only are things like the insulation not as energy-efficient as products that are on the market today, but that your home has had time to wear out elements like weather-stripping and caulking. So you may have more points of entry for the elements to find their way in and for conditioned air to make its way out.
And all of that means you may need an air conditioner with a higher BTU capacity than newer homes may need.
Number of Windows in Your Home
Windows are one of the main culprits of energy loss. Old frames develop air leaks and older glass may not have multiple panes or be as insulating as newer glass.
If you have a lot of windows in your home, and the windows are all (or are mostly all) older, then you have a more significant potential for energy loss. To keep your home at a comfortable temperature, you will need an air conditioner with more BTUs.
Where Is Your Home Located?
If you live in a region where the temperatures soar during warmer months, then you will need an air conditioner that can handle the highs.
Instead of multiplying by 20 for every square foot, you may need to multiply by 30 or 35. Choose the higher end of that scale if your home is older or has a lot of windows with older glass/frames.
Do I Need an HVAC Contractor?
If you used our AC size calculator and know what you need, we recommend comparing top AC brands next.
The only way to get an exact quote on a new air conditioner is to get in touch with a professional contractor. Our research shows that meeting with three to four contractors is the magic number to get the best price on a new system.
Be sure to point out any older windows or other potential energy problems in your home as you are getting quotes.
If you don’t want to spend the time researching and calling contractors, you can click the button below and have Modernize match you with up to four contractors in your area.
Compare top-rated HVAC pros in your area.
Read real homeowner reviews, explore qualifications, and view promotions. Modernize makes it easy to browse professionals and find one that will be perfect for your project.
