How To Tilt A Window Air Conditioner: Should You Even Tilt It? Angle?

Tilted window air conditioner. That’s quite an interesting concept. Many homeowners are asking should a window air conditioner be tilted at all.

This dilemma about window AC being balanced, tilted, tilt angles, and so on is quite simple to answer. If the window AC should be tilted or not depends on only one thing:

Is your window air conditioner leaking water inside?

Yes: As we have written in the article about window AC leaking water indoors, an inward tilted unit can cause the window AC to leak. The inward tilt can prevent the accumulated water to be drained via the drainpipe, located at the back (outdoor side) of the unit.

Even a balanced unit can leak. In this case, tilting the window AC unit outwards makes sense. We are going to talk about how to tilt a unit and what tilt angle you should use (the maximum window AC tilt angle is calculated via the maximum 1/2 inch elevation of the indoor part of the window AC unit.

should you tilt a window ac unit
Window AC tilt determines the access of the drain pipe to the accumulated water in the drain pan.

Of course, if the window AC unit is leaking outside too much, tilting the window AC unit inward might not be the best idea. In all likelihood, you have a partially or completely blocked drain pipe.

No: If you don’t see the window AC unit leaking water, you don’t have to tilt the unit. This is quite simple. There is a myth that if you tilt a window AC at a certain angle, you increase its efficiency (or even reduce noise levels). That’s just a myth; if you don’t see water leaking out of the front (indoor part) of the window AC, you should not tilt your unit.

We will look into how and by how much (tilt angle) window AC unit should be tilted. But first, let’s explain why you should tilt a window AC unit at all:

Why Should A Window Air Conditioner Be Tilted At All?

If air conditioners wouldn’t reduce as dehumidifiers (and reduce moisture levels), we wouldn’t be talking about leaning a window AC unit at all. The main and only reason why these units may be tilted is water accumulation.

Window AC units accumulate water in the drip pan, located at the bottom of the unit. A drain pipe, usually located on the outdoor side, is used to continuously drain the water and prevent the drip pan from overflowing.

In order for the drain pipe to do its job, it has to be in contact with the water accumulated in the drip pan. The drain pipe is nothing more than the pipe; it’s located a bit over the bottom of the window AC.

Inward Tilt

Now, if the window AC is tilted inward, the water is being accumulated at the indoor part of the drip pan. That means the water levels will have to rise substantially before they reach the drain pipe. That means the drain pipe can’t possibly do its job because it has no contact with the water. Higher levels of water may cause the window AC unit to leak water inwards.

Tipping the window AC unit outdoors will help the drain pipe to do its job.

Balanced Window AC Unit

In most cases, we have a balanced window AC unit that is leaking water indoors. Tilting the unit outwards seems like a good idea here, right?

That’s exactly right. This leakage usually occurs when the unit has to work extra hard (high moisture areas) to reduce the indoor relative humidity levels. The result is an increase in accumulated water in the window AC’s drip pan and failure of the drain pipe to drain the water quickly enough.

We will start to see the drip pan overflowing (there is more than 1 culprit of why the drip pan might be overflowing, including the blocked drain pipe; you can read all about the drip pan overflowing here).

To help the window AC unit drain the water quicker, we may tilt it by half an inch. You have to elevate the inward-facing part. We are going to look at how to do this step-by-step further on.

The main thing that you have to figure out when you know you have to tilt a window AC unit is this:

Window AC Tilt Angle (1/2 Inch Or About 1.6°)

What angle should a window AC unit be?

Your unit should be tilted just right. If you tilt it just a bit, it may be too little to prevent indoor leakage. Can you tilt a window AC too much? Of course, you can. When the window AC unit is tilted too much, there is a small chance of the unit falling off the window sill (that’s what many people think of as the first concern).

tilt angle for a small window air conditioner
Tilt angle depends on the width of the unit. Here is the smallest 5,000 BTU window AC unit with a 13-inch width.

The reason concern with AC unit being tilted too much is that the internal parts of the window AC units might not be working as efficiently as when balanced. Anything from dust filter, to fan, evaporator, or condenser coil was created with a balanced window AC in mind. If you tip it too much, something might go wrong due to gravity pulling at too big of an angle.

Now, there is no code that would give you direction of how much should a window AC be tilted. As a general rule of thumb, however, we always say that you should not elevate the inward part by more than 1/2 inch.

When you want to slope a window AC unit, just generally just lift the indoor part by this half of an inch. The angle this makes depends on the width dimension of the unit.

Not to bore you with trigonometry or geometrics, but this is a clear case of a triangle case. If we know how wide the window AC is and that the indoor elevation is 1/2 inch we can calculate the angle the window AC unit is tilted at like this:

Window AC Tilt Angle = Tg-1 (0.5 Inches / Width Of AC Unit)

calculating window ac tilt angle

Basically, we use the tangent function (Tg) to calculate this. We have to figure out how wide is the window AC. We have talked a lot about the window AC dimensions in inches here, but we have only addressed the length and the height of the window you need to be able to install a unit on the window sill.

Here is how wide window AC units are:

  • Smallest 5,000 BTU units are about 13-inches wide.
  • Biggest 25,000 BTU units are about 28-inches wide.
tilt angle for a big window AC unit
Very big 24,500 BTU window AC units have about 28-inch width.

Here is the calculation for both the smallest and the biggest window AC unit tilt angle:

Tilt Angle (Smallest Unit) = Tan (0.5 In / 13 In) = 2.2 degrees (2.2°)

Tilt Angle (Biggest Unit) = Tan (0.5 In / 28 In) = 1.0 degrees (1.0°)

Most AC units are somewhere in between this 1.0 degrees and 2.2 degrees angle. An average window AC unit’s tilt angle is 1.6 degrees.

We can see that this ‘0.5 inches elevation’ general rule gives us very small angles and there’s quite a big difference between 1.0° and 2.2°. Using the equation above, you can calculate how much you have to tilt the inward-facing side of the window AC to get to the average 1.6° angle (if you don’t know how to do it, you can use the comment section below and we’ll help you out).

With the right angle figured out, let’s look at how to tilt a window AC step-by-step:

How To Tilt A Window AC Unit? (Step-By-Step Directions)

Tipping a window AC unit is quite easy in theory. However, if you don’t want to tilt it by too much or too little, you have to make the calculation above. On top of that, you have to adequately underpin the inward part of the unit. If you don’t do that properly, the unit might be unstable and vibrate too much, resulting in an unnecessary noise unit.

Here is the simple step-by-step way how to tilt a window air conditioner:

  1. Determine if the unit has to be tilted at all. Check for indoor water leakage; that’s the main indicator that tells you the window AC unit should indeed be tilted.
  2. Calculate the tilt angle. You can elevate the indoor part by 1/2 inch (rough estimation), or shoot for a 1.6-degree angle (precise estimation). For precise calculation, you will need to know the width of the unit and use a bit of trigonometry.
  3. When you figure out how much you should elevate the indoor part. You have to choose what material to use to put it under the window AC unit. Good choices are a piece of wood, durable plastic, or even cardboard.
  4. Run the unit and make sure it’s stable and produces as little noise as before. You should also see an increase in the window AC unit drainage outdoor. This will reduce the likelihood of water accumulation in the drip pan and unwanted indoor leakage.

All in all, you have all the information about how to tilt a window AC unit here. Of course, should you tilt a window AC unit is another matter (check the indoor leakage). If you have to tilt the AC unit, make sure you choose the right angle and the right material to do it.

We hope this helps somebody from keeping a room with the window AC unit dry.

6 thoughts on “How To Tilt A Window Air Conditioner: Should You Even Tilt It? Angle?”

  1. I have an LG 18000 AC/HEAT window unit. Dimensions are 17” height 26” width
    28 3/4” long. How much tilt should I have.??
    Thank you

    • Hi Jason, the usual recommendation is to tilt it by 0.5 inches (lift the side facing the indoors by 0.5 inches). But as we have seen in the article, this is a bit too simplified a recommendation. The roughly average tilt we calculated is 1.6 degrees.
      In your case, you have a 26″ width; how much to lift it up for the 1.6-degree tilt? Alright, you have to use the sinus function like this: sin 1.6° = Elevation Height / 26″. You express the ‘Elevation Height’ like this: Elavation Height = sin 1.6° * 26″ = 0.73 inches. You have to convert degrees to radians to make this calculation, but all in all, you have to lift your window AC by 0.73 inches to get that 1.6 degree angle. Hope this helps.

  2. How do I drain my drain pan and see if my drain line is clogged up on my window air conditioner? I have a 5-6 thousand but LG unit.

    • Hi Caroline, you should disassemble the unit a bit. You want to remove the front panel and check how to access the drain panel. There should be a hole in the drain panel; check if these is debris or a clog in there, and remove it. You can drain the drain pan by just tilting the window AC unit towards the drain hole, the water should flow through that hole outdoors. Hope this helps.

  3. Hi, I just put in a replacement unit and it ‘appears’ to have no tilt. I’m not sure how to evaluate this (other than wait to see if it leaks inside). Can you tell me? The guy who helped put it in (too heavy for me!) used his smart phone and said it appeared level and we did not know what to do. Do I use a level (how can that assess such a small angle of tilt?!) or how else to assess? Also, what you are calling ‘width’ of the unit seems to me to be the ‘depth’ instead. Looking from the front, the ‘rectangle’ area would be the height X width. Then, how much it goes from front of unit to back of unit would be (to me) the ‘depth.’ Anyway, can you assist me in measuring tilt? THANK YOU

    • Hi Vicky, alright, you might be overthinking this a bit, and that’s good. With a new unit, you don’t have to tilt it. Most units (90%+) will work just fine. If you see window AC leaking indoor, you might put a 1/2 inch of paper under the unit on the indoor-facing side, and that’s usually enough. Hope this helps.


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