Then mathematically and by definition, the more tonnage, the more air the unit can cool in a hour—which leads many to purchase the biggest unit they can afford, thinking that their house will cool faster and they can just turn it down once it reaches “cold.” But bigger tonnage doesn't mean it cools faster; it's simply ...
A undersized system will run more and remove more humidity in cooling, but you give up being able to keep your home at, or near, setpoint on the really hot days. A oversized system in a humid area will not run enough to remove enough moisture from the home and it could cause issues with mold and mildew.
For an Entire House
However, as a shortcut, most HVAC experts agree that you need a 1.5-ton (18,000 BTU) unit for a 1,000-square-foot space, a 2-ton unit for a 1,500-square-foot home, and one additional ton for every 500-square-foot increment.
Since an oversized AC is too powerful for your home, it will quickly cool your home then shut off, which can raise your energy bills and wear out your AC (from all the starts and stops).
However, the truth is an oversized system will not do a better job of cooling the house or provide any extra comfort over a properly sized unit. Air conditioner size is calculated in BTU (British Thermal Units) and tons, and measures how much heat the system can remove from the home in one hour.
For example, when considering what size air conditioner is needed for a 2,000 square foot home, you would likely choose a 3 or 3.5 ton unit, depending on the climate where you live.
Then mathematically and by definition, the more tonnage, the more air the unit can cool in a hour—which leads many to purchase the biggest unit they can afford, thinking that their house will cool faster and they can just turn it down once it reaches “cold.” But bigger tonnage doesn't mean it cools faster; it's simply ...
Your air conditioning system is one of the biggest culprits behind skyrocketing electric bills. When your air filter is dirty, refrigerant levels are low, your thermostat is faulty or you lack proper maintenance, your A/C system can end up using a lot more energy than it should.
3.5 Tons (42,000 BTUs): Suitable for homes ranging from 2,100 to 2,400 square feet. Installation cost ranges from $3,800 to $5,500. 4 Tons (48,000 BTUs): Suitable for homes ranging from 2,400 to 2,700 square feet. Installation cost ranges from $4,000 to $6,000.
Most times, we believe that a mini-split system is worth the cost. Not only can it be an affordable and versatile alternative to a traditional HVAC system, but they can also save money in the long run with how efficient they are.
As a general rule of thumb, a 3-ton AC unit is typically capable of cooling approximately 1,200 to 1,500 square feet. However, it is always recommended to consult with a professional HVAC technician to determine the appropriate size of the AC unit for your specific needs.
Higher Utility Bills
A bigger unit simply gobbles more power than a smaller one. To make matters worse, your oversized air conditioner will likely never reach its promised level of energy efficiency. Just as it is cycling up to its most efficient level, the thermostat will tell it to shut off again.
The right tonnage ensures that the AC can effectively cool the space without overworking. Choosing the correct tonnage directly affects the cooling efficiency of the unit. If the AC is undersized for the room, it will struggle to cool the space adequately, leading to longer running times and higher energy consumption.
Is It Better to Oversize or Undersize AC Unit? Neither oversizing nor undersizing your AC unit is ideal. Both scenarios can lead to issues with efficiency, comfort, and longevity of the system.
If your air conditioning system is too big, it cannot completely cool your home. This means that you'll have hot or cold spots throughout your home. An AC system that is too large doesn't run long, so the cool air can't be equally distributed through your home. This causes some areas to be cool while others are warm.
But when an oversized unit is in place, it cools far faster and limits the cycle, which causes muggy, damp conditions in many cases due to high humidity. This can also lead to mold formation and a musty, uncomfortable smell.
If your air conditioner is too big, you'll have hot spots – or inconsistent cooling – throughout your home. Hot spots occur most often when cold air doesn't disperse through the home efficiently enough. You'll notice that some of your rooms are cool and comfortable, while others are hot and humid.
BTU: British Thermal Units
This is probably the most important of the air conditioner ratings as this is what tells you how much space the unit can cool. One BTU is the amount of heat that is needed to raise a pound of water on degree Fahrenheit.
For those of you that don't understand the way AC systems work, a 2-ton unit typically provides cooling for about 900-1,400 square feet of space – give or take.
The average cost of installing a new central air conditioner in 2024, including equipment and labor costs, is $5,750 for a 3-ton unit in a 2,000-square-foot home. On average, a new AC unit cost will fall between $3,300 and $7,800.
While every unit is different, and every homeowner has a different understanding of when their central air conditioner is broken beyond repair, it's fair to say that, with proper maintenance and care, you can expect a good 15 to 20 years of cooling from a new high efficiency air conditioning system.
Homes measuring 1,000-1,500 square feet: You'll need a 2-ton unit, which corresponds to a cooling capacity of 24,000 BTUs per hour. Homes measuring 1,500-2,000 square feet: You'll require a 3-ton unit, equivalent to 36,000 BTUs per hour. Homes measuring 2,000-2,500 square feet: A 4-ton unit is necessary.