Choosing An Air Conditioner: How Many BTUs Do I Need?

If you’ve been looking at air conditioners, you’ve probably encountered something called a BTU rating. While defining what a BTU rating is gets a bit complicated, in short, when talking about air conditioners, the BTU rating corresponds to how much space an air conditioner can adequately cool.

Getting an AC unit with an adequate BTU rating is important – too little power, and your AC unit won’t cool your room, too much, and you run into other problems like inefficiency and feature failure – but figuring out how much you need might be a bit of a head scratcher. Luckily, AppliancePartsPros.com is here with another great guide. In this tutorial, we’re teaching you about BTUs, what they are, why the right rating is important, and how to figure out what BTU rating you need for your home. By the end, you should be well on your way to purchasing an air conditioner that’s right for you.

Let’s get started!

What Are BTUs?

The British thermal unit (BTU) is a measure of energy required to produce a certain amount of heat. You may have seen the value before, represented either as a full number (14,000 BTU) or an abbreviated number (14k BTU); BTU ratings are assigned to appliances like ranges, solar water heaters, fire pits, furnaces, and, of course, air conditioners. The actual definition of BTU is the amount of energy required to raise the temperature of one pound of water by one degree Fahrenheit – but what does that mean for air conditioners?

Simply put, the BTU rating of an air conditioner tells you how much heat a unit can remove from nearby air per hour. The higher the BTU rating, the more space an air conditioning unit is capable of cooling. That may sound like a case of bigger is better, but don’t rush out to buy the highest BTU rating AC unit you can find. In the next sections, we’ll review why you should purchase an AC unit with a BTU rating appropriate for your home’s size.

Why It’s Important To Have The Right BTU Rating

At first glance, it may seem like going with an AC unit with a high BTU rating is the way to go, but that isn’t the case. An AC unit that’s too powerful for the room it’s in can be more of an annoyance than a benefit.

If your AC unit’s BTU rating is higher than what is needed:

• It will cycle on and off more quickly. That doesn’t just mean more annoying noise – the process will tax the unit’s components more quickly, shortening the AC unit’s lifespan.
• That increased cycling frequency also lowers efficiency, which means a higher electric bill.
• It may also interfere with features like humidity control and air filtering – that quick cycling means those features won’t run as long as they need to to work.
• The higher the BTU rating, the more expensive the AC unit, so you may have paid way more than you needed for something that may end up costing you more in the long run.

And what if you’ve got an AC unit with an insufficient BTU rating?

• First and foremost, it likely won’t adequately cool the room it’s in, in general.
• If your AC unit has humidity control or air filter features, it likely will fail to completely filter or remove humidity from the air, resulting in a cooler but still musty/humid room.
• You’ll likely see a higher electric bill than you should. AC units are big power eaters in general, but an AC unit with an inadequate BTU rating will run constantly to try and reach an appropriate temperature, resulting in more electricity consumed.
• The AC unit will wear out faster, because it’s working harder to cool the room.

How Many BTUs Does My Air Conditioner Need?

To figure out the BTU rating you need, you’re going to need to do some math, so it’s time to grab that calculator. Here’s what you need to know about calculating the BTU rating you’ll need for your AC unit:

• To start, you’re going to need the total square footage (length, width, and height) of the room you want to cool  – that includes things like closet space. If you don’t have this information readily available, grab a measuring tape.
  • Measure the length and width of the room in feet and inches, then multiply those two numbers together to get your square footage.
  • If you’re working with a triangular room, multiply the length and width, then divide that number by two.
  • For more complex room shapes, like circular or rhomboid rooms, divide the room into smaller squares and triangles, then use the above methods to get your total.
• BTU calculations put out by Energy Star and the EPA assume that you have 8ft between floor and ceiling. If your ceilings are lower or higher, you may need to use an online BTU calculator to get a more appropriate rating for your needs.
• The EPA estimates that 20 BTU are needed for every 1 square foot of space, however, this estimate is a bit conservative. Instead, check out the Energy Star estimates:

Square Footage	BTU/hr needed
100 – 150	5,000
150 – 250	6,000
250 – 300	7,000
300 – 350	8,000
350 – 400	9,000
400 – 450	10,000
450 – 550	12,000
550 – 700	14,000
700 – 1,000	18,000
1,000 – 1,200	21,000
1,200 – 1,400	23,000
1,400 – 1,500	24,000
1,500 – 2,000	30,000
2,000 – 2,500	34,000

Once you’ve got your number, you’ll need to make some adjustments based on certain circumstances:

• If you’re cooling your kitchen, increase the number by 4,000 BTUs to account for the appliances running in there.
• If more than two people regularly occupy a room, add 600 BTUs for each additional person.
• If the room is heavily shaded (doesn’t get a lot of sun exposure or has few windows), reduce the number by 10%.
• If the room is frequently in direct sunlight, increase the number by 10%.
• How well insulated is the room you want to cool? If there are gaps under doors or around windows or cracks in the wall, this will affect how hard your AC unit needs to work to cool the room. We can’t give a specific number to account for these issues – it’s best to try your best to fix any issues with insulation before installing an air conditioner in a room, but if that isn’t an option, a slightly higher BTU rating should help to account for the difference.

Now, after all this math, you should be left with the appropriate BTU/hr rating for the space you want to cool. Next up – which AC unit to buy!

How to Find An AC Unit That Fits My Needs

Now that you know what BTU rating to shoot for, you can start shopping around for air conditioning options. Let’s take a look at air conditioner BTU ranges.

• Portable air conditioners can run from between 8,000 BTU to 14,000 BTU. Definitely more than adequate for cooling most average-sized rooms, potentially tipping into overkill.

• Window AC Units typically have a capacity between 5,000 and 12,500 BTU, making them appropriate for most average-sized rooms.
• Ductless mini-splits come in a wide range, from as little as 9,000 BTU for a single room, more whole-house options that have ratings up to 48,000 BTU.
• Central air will cool your whole home. For residential properties, you can expect to see between 20,000 and 50,000 BTUs.

With an idea of what type of AC unit you need, you can now consider other features, like SEER ratio (higher is better, sort of like how many mpg your car gets), how quiet a unit runs, and extra features like timers, air filtering, and humidity control.

We recommend these four ductless split MRCOOL units to our customers, based on their square footage. They are easy to install yourself and cool/heat your home the whole year round. The BTU units are expressed in thousands, 12 BTU = 12,000 BTU units as referenced above.

The 12 BTU can cool and heat 500 square feet : https://www.appliancepartspros.com/mrcool-energy-star-diy-12-hp-115b25-ap7192776.html

The 18 BTU can cool and heat 750 square feet: https://www.appliancepartspros.com/mrcool-energy-star-diy-18-hp-230b25-ap7192779.html

The 24 BTU can cool and heat  1000 square feet: https://www.appliancepartspros.com/mrcool-energy-star-diy-24-hp-230b25-ap7192782.html

Getting The Most Out Of Your Cooling System

Before we wrap up, here are a few extra tips to get the most efficiency out of your cooling system, whatever you use:

• Make sure your AC unit is venting in an appropriate way – vents should be pointed in the direction of the area you want to cool and should be kept clean and free of anything that might block them. If installing your AC unit in a corner, make sure it is able to direct airflow out into the room.
• Keep condenser coils clear of dust and debris! This can drastically increase efficiency and lower your electric bill.
• If you can, make sure your thermostat is installed in a place where it isn’t exposed to appliances or lamps that produce excess heat. It will misread the temperature in the room.
• Check for gaps in windows, doors, and walls, and seal them up to ensure your room is properly insulated.
• Keep curtains and blinds closed to keep heat from the sun out.

We hope this guide has made BTU ratings a bit easier to understand. Once you’ve got yourself set up with the perfect cooling system for your home, why not head back our way to see how else AppliancePartsPros.com can help? Whether you’re in search of cleaning tips, DIY tutorials, or the replacement parts you need to keep your appliances in tip-top shape, you can find it here!

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