What Size Air Conditioner Do I Need?

Air conditioners are incredibly useful for keeping your home at a comfortable temperature. If you live somewhere with very hot summers or that is very humid, then you will find that having a good air conditioner can be the difference between suffering through sweaty days and sleepless nights, or being comfortable at home all year round.

Getting the right unit

Air conditioners are complex machines, and it is important that you get the right type for your needs. If the air conditioner is too small or too large, then you will find that it doesn’t run efficiently; you will be wasting power and sacrificing comfort too.

What happens if it is too small?

If you have an air conditioner that is too small, then you will find that it cannot effectively cool your home. It will run permanently, starting a cycle, monitoring the temperature of the air and never finishing that cycle because the air in your property doesn’t reach the target temperature. A standard air conditioning unit’s cycle should last 20-30 minutes. If yours runs for a lot longer than that, or will not stop running, then there is a high chance that your unit is too small. A unit that is too small costs more to run and will either leave you with a property that never quite gets cool enough or one where the temperature is patchy throughout the house.

Problems With Having Too Big of a Unit

If having too small of a unit is a problem, then one natural conclusion is just to buy the biggest unit that you can. Unfortunately, it is possible to have a unit that is too big. Bigger does not always mean better in the world of air conditioning.

If your AC unit is too big, then you may find that it is very noisy when in operation. The noise might be so bad that it keeps you awake at night. In addition, bigger air conditioning units will cool the air much more quickly, and that can cause humidity problems. With an air conditioner that is correctly sized, the air will cool as it passes over the unit’s coil, and water vapor will form on the coil itself. When you have a unit that is too big, instead of the air reaching its dew point as it passes over the coil, it will condense more quickly, and this can lead to a sticky, humid feeling in your home. Having too much humidity often can lead to mold and dust mite problems.

In addition, just as a small air conditioner is inefficient because it is running all the time, powering a bigger air conditioner than you need is a waste of energy too. It is much less expensive to run an appropriately-sized air conditioner.

How to Determine the Perfect HVAC Unit Size

To determine the required power of an air conditioning unit, you need to perform a load calculation. This will give you a reading of ‘BTUs’ (British Thermal Units), which is the strength of the air conditioner. This takes into account several factors, including the area size, the number of people who are usually in the property and the number of windows the property has as well as what the rooms are used for. The formulas required to do this are quite complex since you will need to know the size of the property, the size of the windows, which direction the windows face, and the power and type of any appliances and lighting in the room.

You can find free HVAC Thermal Load Calculator tools online that will help you to perform these calculations. It is always a good idea to have your air conditioning contractor do the calculation for you, and if you have any concerns about the results that they come up with, sanity check them yourself later.



The Different Types of Units Available

There are several different kinds of air conditioner available, including central air conditioners and heat pumps which are designed to heat or cool the entire property, as well as ductless mini air conditioners, room air conditioners, and evaporative coolers. These all work slightly differently, and choosing the right type is as important as choosing the right size.

Room air conditioners can be mounted onto windows and are handy if your property is older and it would be hard to install a central air conditioner, or if you just want to cool one particular room. Ductless mini air conditioners are an excellent choice for very small areas as well. Evaporative coolers release moisture into the room as they work, which makes them a good choice for dry climates and for people who have certain respiratory conditions. These coolers are less effective in environments that are already humid, however, so it is prudent to seek advice from a specialist contractor before you spend a lot of money on a cooling system.