Air Conditioner (Heat Pump) Replacement / Installation

How To Size An Air Conditioner

It’s really important to size an air conditioner correctly. The reason for this is simple. If you get the size wrong, it won’t operate as well as it should. So check-out Hilltop Plumbing’s quick guide on how to size an air conditioning unit!

It’s really important to size your air conditioning unit correctly.

The reason for this is simple. If you get the size wrong, it won’t operate as well as it should.

In other words, if your unit is too big for the space you’ve chosen, its compressor won’t run long enough to properly dehumidify your house.

Worse yet, the more unnecessary space your AC unit has, the harder it will have to work to generate cool air, which means you will end up paying the price in higher electricity bills.

So, in order to help you out, here’s our guide on how to size an air conditioner.

But before we get to that, it’s worth noting that there are lots of different kinds of air conditioners, and the type you choose to purchase will have an impact on how you size it.

Different kinds of air conditioners

Window unit air conditioners

These can be installed either in a single a or double-hung window and they usually come with ‘accordion panels’ which can help ensure a tight fit.

Built-in air conditioners

These are permanent units that are installed on your wall. They generate both cold and hot air. They tend to be more expensive than ordinary window units. However, on the plus side, they don’t take up valuable space on your window.

Freestanding air conditioners

These can be shifted between rooms and located in any space in your house. One downside is that you might have to drain them every now and again, as they tend to build up reservoirs of moisture. 

 Getting the right size unit for the right size space

The British thermal unit – or BTU – is a rating system that tells you how rapidly and efficiently any given AC unit can cool a room.

The rating scale tends to range from around 5,000 BTUs to upward of 20,000.

A unit with a low BTU rating will struggle to cool a big room. However, an oversized air conditioner in a small room will accelerate on and off, which wastes a whole lot of energy!

Don’t ignore other factors, either.

Ceiling height, room insulation, light exposure, location and – of course – the climate of the part of the world you live in will all have a bearing on the BTU number of a room and, therefore, on what size of AC unit you need.

In fact, there’s a basic sizing formula that can help you work out what kind of AC unit you’ll need for your room.

For brightly lit rooms, go for a unit that provides ten percent more BTUs than what is otherwise required by the room size.

For your kitchen, go for a unit with an extra 4,000 BTUs than what is required.

And for rooms that usually have more than two people in them, add an upwards of 600 BTUs per person.

How to calculate the size of a BTU or AC unit

Here’s another way of finding out how to size an air conditioner: multiply the length times the width of the room or area to be cooled, then multiply that number by 25 BTU.

This system will guarantee that your room is adequately cooled.

Why it’s best to get a specialist fitter

Of course, if you want to ensure that your AC unit is properly sized and installed, the best thing to do is to hire a professional team to come and measure your home.

So if you really want to know how to size an air conditioner, the experts here at Hilltop are always ready to help!

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