Visual Guide to Determining the Right Sized Air Conditioner for Your Home

In the heat of the summer, many people turn to air conditioners to help keep comfortable indoors. A single room air conditioner is a very effective way of cooling a specific area of the home, and is a great alternative to central air conditioning for smaller spaces, homes without ductwork, and for homes located in areas where you only need the air conditioner a few days a year.

But what many homeowners may not realize is that room air conditioners need to be sized properly to be the most effective. Too small and they may not cool properly. Too large and they will waste energy and raise your bills, without providing you with any additional benefits.

Taking information from Energy Star, we’ve created this graph to help you better understand the best air conditioner for your needs.

Room Size and Circumstances Determine the Right Size for Your Air Conditioner

Air conditioners work by exchanging air, condensing it and cooling it as it moves from outside to indoors. And each air conditioner can only handle so much volume before it becomes ineffective. That’s why it’s important to choose the right sized air conditioner. A unit that’s too small will struggle to keep up with the demand in the room, while a unit that’s too large will use more energy to complete the same task as a smaller, better sized unit.

Air conditioners are labeled by the number of British Thermal Units (BTUs) that they expend. It’s important to know just how many BTUs are necessary to cool a space. The graph helps break this down for you easily; it shows you the number of BTUs necessary for a room’s size.

Because there are factors that can alter the number of BTUs beyond the room’s size, the graph shows you the size of air conditioner you will need not only for square footage, but also when used in a kitchen, in a sunny area, and if the space is heavily shaded. You can see the difference easily for what is required. For example, a room measuring 150 square feet only needs 4,500 BTUs if it’s in a shaded area, but the same size space needs 9,000 BTUs if the unit is cooling a kitchen, which tends to become more easily heated with cooking appliances.

Other Factors to Consider

Size is the biggest factor to consider when choosing an air conditioner, but it’s far from the only one. There are several other considerations you may need to make to choose the best air conditioner for your needs.


Not all air conditioners are created equally. Some may be inexpensive, but they can cost you more long term both in energy consumption and by wearing out more quickly and requiring either repairs or replacements.

When selecting an air conditioning unit, check for a couple of things. The first is how efficient it is; Energy Star rated air conditioners will use less energy than standard models. The second is how good the warranty is. Better quality models will have longer warranties and will protect against more issues, ensuring that the unit will last longer.

SEER Number

If you plan on using your room air conditioner on a regular basis, then you will want to ensure that you purchase a more efficient model. Most air conditioner units will display their efficiency in a number known as SEER - Seasonal Energy Efficiency Rating. A SEER of 13 is considered an efficient model, but a unit that has a higher SEER will save you even more. The highest SEER units will cost more up front, but will save you the most long term.


Most room air conditioners will have additional features beyond a temperature setting. Programmable thermostats, remote controls, fan speed settings, and more are all options on today’s air conditioners. When determining the right unit for your needs, be sure to weigh these features as well. Having a programmable thermostat can help you save more, while varying settings can help you control your comfort level better. Take a look at the features available and determine which ones you will you use the most to determine the best unit for your needs.

Make an Informed Decision

Air conditioners can help you stay cool and comfortable in the summer heat. But if you choose the wrong sized unit, it may not function as well as you had hoped. Make sure you pay attention to the room’s size and location when selecting your unit, and that you factor in things like warranty and efficiency as well as features. In the end, you’re sure to have an air conditioner that can help keep you cool for many years to come.