Here’s something that happens a lot. We’ll either get a call from a homeowner or a customer will ask us during a service call. It starts with a simple question:
“What size air conditioner do I need for a 2,000 square foot house?”
Or maybe the house is 1,500 square feet. Or 3,000. It really doesn’t matter because the answer is always the same.
There’s no way to know what size AC you need until we perform a Manual J load calculation.
This calculation is a series of exercises an HVAC consultant should perform to determine the right AC size for your home. In arriving at the correct size, the design engineer will take a variety of measurements throughout your home and take note of several key attributes. Ultimately, the right AC might be a 2 ton, 3 ton, 4 ton, or even 5 ton unit! Everyone’s home is unique and different, regardless of square footage.
Instead of going to all that trouble, could we just hazard a guess? Maybe. But a guess is still a guess.
And we don’t think you should spend thousands of dollars on somebody else’s best guess.
The limitations of “rules of thumb”
Many HVAC contractors will happily provide a very specific answer to your question about the AC in the 2,000 square foot home. Depending on whom you ask, you might be advised to purchase a 3.5 ton unit. Other contractors will steer you toward 4 tons.
In our climate zone, these would be the “normal” AC sizes for your 2,000 square foot home. Most contractors will pick one size or the other and install the AC without a second thought.
But this is a big mistake.
Contractors’ rules of thumb fail to consider a lot of really major factors that impact the AC size you should select for your home. These factors include:
- Orientation of the home relative to the sun
- Number of windows, their sizes, and locations
- Number and locations of exterior doors
- Insulation levels in the attics, crawlspace, and walls
- Room-by-room ceiling height
- Attic knee wall specifications
Do you see why two different 2,000 square foot homes might have vastly different heating and cooling needs? Square footage is just one factor to consider when sizing an air conditioner; it’s far from the only factor.
Sizing an AC based on square footage is like tailoring an entire suit based solely on somebody’s inseam. By not taking all of the necessary measurements, you will probably end up with something too big or too small.
And in the Atlanta region, what we usually find are air conditioners that are way too big for the homes where they’re installed.
Perils of oversizing your air conditioner
Ok, let’s say you decided to hire the contractor who said your 2,000 square foot home needed a 4 ton air conditioner. If it turns out that 3 tons was actually closer to the right size, what’s the harm? Doesn’t 4 tons just mean you have more cooling capacity when you need it?
Sadly, this is not the case. Contractors often oversize HVAC equipment because they’re worried about not giving you enough cooling or heating capacity. But an AC that’s too big can cause all sorts of problems, such as:
- High summertime humidity: Have you ever wondered why you still feel hot even though the thermostat says it’s 74 degrees? In homes with oversized air conditioners, the AC doesn’t usually run long enough to remove much humidity from the home. You’re uncomfortable because the humidity is still high, even though the AC satisfied your thermostat setting.
- Inconsistent or uneven temperatures: An oversized AC will cool your home really quickly. What ends up happening is that some areas feel really cold while other areas still feel hot. This is because the AC doesn’t run long enough to distribute the cool air throughout your home.
- High energy bills: Since they satisfy the thermostat setting so quickly, oversized air conditioners turn on and off a lot. This is called short cycling, and it’s very expensive. AC’s consume most of their energy during startup; therefore, the more frequently your AC starts up, the more you spend on cooling.
The solution to these problems is to get the AC size right from the start. Don’t listen to the guy who says you need a 4 ton unit without so much as pulling out a tape measure! The right way to size your AC is to have a pro perform a Manual J load calculation.
The right way to calculate AC size
Earlier, we discussed some of the factors involved in determining the right size AC for your home. Any time we’re tasked with a new air conditioner installation, we take the time to record a variety of measurements from throughout your home. Then we enter that information into a software application.
The application crunches the numbers for us and tells us what size AC your home needs. Basically, we do the data entry and the computer performs the Manual J load calculation.
One advantage of having an HVAC pro perform this step is that we’ve done a lot of load calculations before. On the rare occasion where the result seems odd based on our experience taking measurements throughout the home, we know how to review our work to identify any issues with the data we gathered. People with less experience might not realize when something is amiss with the results.
We do this before every new air conditioner installation. The way we see it, performing a load calculation prior to an installation is a critical part of professional HVAC ethics.
In the end, you will get the right size AC for your home. You’ll enjoy the best possible comfort and efficiency, not to mention a longer lifespan for the equipment.
So, can we really answer the question, “What size air conditioner do I need for a 2,000 square foot house?”
Yes! We can answer it. But only after we perform the load calculation.
And the size we recommend isn’t ever the right size for just any 2,000 square foot house. It’s the size that’s right for your 2,000 square foot house.
At PV Heating & Air, we perform on-site load calculations at homes in Metro Atlanta. In addition, we provide load calculations to clients nationwide who are able to provide the necessary data about their homes. To learn more or schedule a load calculation at your home, give us a call at (404) 994-2229 or fill out the form below!