Air Conditioner BTUs?

BTU – Air Conditioning Lingo Confusion

Have you ever shopped for a window air conditioner or a portable ac and realized that there is certain language right on the outside of the box that supposedly tells you everything you need to know about the AC?

But the problem is no one seems to know what that language means?

The specific term I’m talking about is BTU.

What are Air Conditioning BTU’s?

BTU stands for British thermal unit. It is the amount of energy needed to heat or cool 1 lb. of water 1° f at sea level.

That tells me everything I need to know. Not.

The funny thing is, never in my life have I ever known what a BTU is. And I’ve never met anyone that did either.

Seems like an odd way to label an air conditioner when not too many people really seem to know what it is.

But if you’re shopping for a new AC, it’s a term you better become familiar with pretty quickly.

Room SizeSquare FootageHow Many BTUs?How Many Watts Used Per Hr
10 x 151505000 BTU1465 w
12 x 121445000 BTU1465 w
14 x 142006000 BTU1758 w
12 x151806000 BTU1758 w
20 x 204008000 BTU2344 w
18 x 2545010000 BTU2930 w
20 x 2550010000 BTU2930 w
25 x 3075015000 BTU4396 w
30 x 3090018000 BTU5275 w
30 x 35100025000 BTU Range7326 w
35 x 40140035000 BTU Range10250 w
38 x 40150037500BTU Range10990 w
40 x 45180045000 BTU Range13188 w
45 x 50225055000 BTU Range16118 w
50 x 50250062500 BTU Range18316 w

Let’s get down to the nitty gritty.

Hhow many BTUs do I need_

How many BTUs do I need? What size air conditioner do I need?

The quickest way to give you a ballpark figure of how many BTUs you need is to use a simple formula.

Square footage (length times width)  x 25

This is a rough figure based on a square room with average 8 ft ceilings and one or two windows that are not directly in the Sun.

If the area you are looking to cool off has higher ceilings, increase the amount by 10%.

Likewise if the room is the direct path of the sun, increase the amount 10% again.

Another factor to consider is the kitchen.

Are you trying to cool off the kitchen or is the kitchen in the vicinity that is adding heat into the area you’re trying to cool off?

If that’s the case then increase the amount of BTUs by 4,000 to combat the extra heat given off by the stove and other cooking equipment.

If you’re dealing with the Arizona Sun or any other high heat climate, tackle on another 10 to 12% of BTUs.

Don’t overdo it.

Bigger is not better when it comes to air conditioners

You might think that if your room requires 5000 BTU then getting an AC that has 8,000 BTU could only add more power and do a way better job.

Not so.

That might be  hard fact to accept for those of us who want bigger and better,

But putting too big of an air conditioner into too small of a square footage will cause humidity to build up in your room.

Humidity is not the result you were going for, presumably.

Humidity makes the room feel hotter than the temperature actually is.

Too large of an AC in too small of a space will not allow for the condensation in the unit to properly displace, which will cause it to evaporate and come back into the room as humidity.

A large AC and a small room will also cycle on and off much faster and use much more energy.

The same ratio can happen with an AC that is too small and a large room except for the AC will continually run without turning off and use much more energy.

how many BTU's per watt

What are BTUs in Watts?

How many watts an air conditioner is going to use is also a big variable when it comes to shopping for an AC.

1 BTU is worth .293071 watts per hour

Energy cost from running the AC is one of the biggest energy hogs you will have in your house hands down.

Energy saving is a must during the summer. Running the AC day and night will put your electric bill through the roof.
So finding some ways to keep cool rather than the AC is always a smart thing to do.

A few tips to keep cool in summer

1.  Bump your thermostat up

Most of us want the kind of cool air you get when you walk into a hotel lobby or a department store in our house.
But the reality is the comfort comes with a hefty price tag.
Simply learning to keep the thermostat a little higher and being comfortable in a little warmer space will have dramatic results on your energy bill. By just going from 72° to 75 on your thermostat, you could see a surprising change in the amount of your bill.

2.  Ceiling fans

Ceiling fans, well technically do nothing to change the actual temperature, they do pull heat away from you so that you actually feel cooler in hot weather. Ceiling fans are much less expensive to run than the air conditioner also.

3.  Shade

Shade can come in the form of plants, shutters, curtains, etc.

Shading your windows can have a great effect on the amount of heat that comes into your room.

Summing it up

Choosing an AC with the proper BTUs for the size room that you want to cool is a must.

But how many people do you know that really know what a BTU is or what they’re supposed to do with that term?

BTU stands for British thermal unit.
If you’re in the HVAC industry or deal with heating and air very much then it is a term or an acronym that you are probably very familiar with and no how to use properly,

But for the rest of us, there is an easier way to determine how many BTUs you are going to need when purchasing an AC.

An easy formula is to take the square footage of a room and multiply by 25.
W x L x 25
And since we all know that rooms come in all different kinds of sizes, we simply add in 10% if the ceilings are higher or if it’s a particularly warm room that sits in the Sun.

It’s also important to know that when it comes to purchasing an AC, more BTUs does not equate to a cooler room.

Two large of an AC will cycle on and off too quickly and will not displace the condensation quickly enough which will cause your room to be extra humid.

An AC should help reduce humidity, definitely not add to it.

You should also be aware that the more BTUs and air conditioner has, the more watts it’s going to consume, and the higher the energy bill is going to be to run the unit.

Published by

Dennis Reed

Dennis Reed Owner and Author @