Time to add some cooling to your home and wondering what size unit you need? Maybe a 2.5-ton vs a 3-ton air conditioner?

Here’s a tip, bigger isn’t always better.

Here’s another tip, and this one is critical. Properly sizing any HVAC appliance is based on a whole lot of math, not guestimates or estimates. But yes, estimates are easier to come by. And they’re free.

And manufacturers do provide estimates, which helps homeowners narrow down their choices.

For example, a 30,000 BTU, 2.5-ton air conditioner is made to effectively cool a home between 1,200 and 1,500 square feet. A slightly larger 3,600, 3-ton unit, is designed for homes that are 1,500 to 1,800 square feet.

But as I said, this is an estimate, and you shouldn’t buy a 3-ton air conditioning unit just because your home is 1,600 square feet. So what should you do and why?

First, and because estimates are beneficial, I’ll provide the size you probably should be looking at based on your home size. Then I’ll explain how you take that ballpark estimate and make sure it really is the right size for your home. Because maybe you should be buying something smaller.

Estimating the Right Size Air Conditioning Unit for Your Home

As mentioned, the HVAC industry does provide general guidelines for sizing an air conditioner. And it’s good to have these in your head before you call several of your local HVAC professionals to come and give you quotes. Because knowledge is power.

2 air conditioner
Check guidelines for sizing of air conditioners before calling your local HVAC

How Air Conditioner Sizes are Measured

The cooling capacity of an air conditioner is based on the number—in tons—of British Thermal Units (BTUs) it can remove in an hour.

The industry standard for central air conditioning units is that they begin from a minimum size of 1.5 tons and get larger in half-ton sizes. So, 1.5-ton, 2-ton, 2.5-ton, and so on. And each half-ton will cool an estimated 750 to 1,000 square feet of space.

Here are your ballpark estimates. But please note these are at the higher end of the scale, not the lower end.

Air Conditioner SizeHome Size
1.5-ton unit (18,000 BTUs)1,500 square foot home
2-ton unit (24,000 BTUs)2,000 square foot home
2.5-ton unit (30,000 BTUs)2,500 square foot home
3-ton unit (36,000 BTUs)3,000 square foot home
3.5-ton unit (42,000 BTUs)3,500 square foot home

From there, things get much more granular.

One extremely important piece of data needs to be calculated into the equation when sizing HVAC equipment. Where you live, and how hot it is there.

The HVAC industry uses zones for this, typically zones 1 through 5.

map showing the climate zone
Where you live and your climate are important in sizing HVAC system

Let’s do some comparisons of the three sizes we’re specifically talking about. 2, 2.5, and 3-ton air conditioners. And I’ll use zone 1 and zone 5. The hottest and coldest zones respectively.

If you have a 1,200 square foot home and live in a hotter climate, depending on a lot of variables, you could need a 2 (24,000 BTUs) or 2.5-ton (30,000 BTUs) unit. But if you live in a cold climate, a 2.5-ton unit will likely be oversized.

Here’s another example.

If you live in a home that’s about 1,800 square feet, has standard 8-foot ceilings, average sun exposure, and it’s a cold climate, you’ll probably need a 3-ton, (36,000 BTUs) unit. Change that to a hot climate, and you’ll need to upsize that to a 3.5-ton (42,000 BTUs) unit. Assuming all variables remain the same.

What are the Variables?

I mentioned a few variables that will impact what size equipment you need, but that is just the tip of the iceberg.

bedroom with big windows
Windows are one of the variables you need to consider for your HVAC system

Here’s a list of variables that an HVAC professional will take into consideration when properly calculating the size.

  • Appliances.  Are you cooling your kitchen as well? Or your laundry room? Appliances that give off heat are a variable.
  • Building Materials. Is your home made of brick? Stucco? Siding? All will impact heat gain differently.
  • Ceiling height. If you have higher than standard ceilings, this can create a cooling deficit due to the increased volume of air.
  • Climate. If you live in a hotter climate, you’ll probably need a larger unit.
  • Electronics. Just like appliances above, your electronics give off heat.
  • Insulation. What R-value is your insulation, and how much of it do you have?
  • Lighting. The type and amount of lighting in your home will impact heat gain.
  • Occupants. Yes, your body gives off heat.
  • Windows. The area of windows in your home. What direction they face, and how many hours of direct sunlight you get. Do you have any natural shading against the house? Trees, hedges, and so forth.

How to Properly Size an Air Conditioner

First, this can be done by the homeowner, assuming they can wrap their heads around it. And there are proper heat load calculators you can find online, but still, the process is fairly complex.

So what is heat load?

If you add up all the conditions I mentioned above, you’ll get your heat load—sometimes called heat gain. And the sum will be expressed in either BTUs or Kilowatts.

This sum is important because your air conditioner needs to be sized big enough to be greater than the heat gain.

Everything that’s going on on the other side of our doors and windows—temperature-wise, at least—has an impact on the interior temperature of our homes. Heat load simply refers to the amount of heating or cooling that is necessary to counteract it, allowing us to be comfortable inside.

Here is the method to calculate your HVAC load.

  • Step 1. Take the square footage of the area to be cooled and multiply by 31.25
  • Step 2. Calculate heat gain through your windows and then multiply that amount times 1.4, assuming you have no shading against your south-facing windows. Note that you would only use 1.4 under these specific conditions. The number would change if you had, for example, south-facing windows with no shading.
  • Step 3. Calculate the heat generated by each occupant, using 600 BTUs per person.
  • Step 4. Add up all the heat generated by all appliances and electronics in the home, using the power wattage for each, and then multiply by 3.4.
  • Step 5. Add up the total wattage used by all household lighting, and then multiply by 4.25.
  • Step 6. Add the totals of steps one through five to find your total heat load.

In theory, adding up all those BTUs should provide you with the HVAC load necessary to heat or cool a home.

Completely lost? Not surprising. And this is why getting a professional in to suggest a proper size based on their load calculations is the best idea.

Having said that, you’ll find that even some pros want to cut corners and ballpark the number for you. And that means you could end up with a unit that is too big or too small for your home. Either will be inefficient in your space and will end up costing you more in operating costs than it should.

If you have a pro that doesn’t want to do a proper job right from the get-go, do you really want them installing equipment in your home? Think about that for a bit.

Conclusion

So, which size is better for you? Should you go with a 2 ton, 2.5 ton, or 3-ton air conditioner? Well, if you made it through all of the above without your eyes crossing, you’ll know I can’t answer that for you.

Or at least I can’t answer that with any degree of certainty. And you want certainty because uncertainty won’t come cheap in this case.

But I can provide you with vague, loose, estimates.

2-ton unit (24,000 BTUs)2,000 square foot home
2.5-ton unit (30,000 BTUs)2,500 square foot home
3-ton unit (36,000 BTUs)3,000 square foot home

Thanks for reading! Hopefully, we’ve provided some useful information. And while you’re here, why not check out the related articles below? Maybe we can help you with something else as well.