How Much Should a Window Air Conditioner Be Tilted?

Air conditioners are a tremendous asset to a home. They regulate the temperature, humidity, and air quality, allowing you to operate with full control over the environment.

How you install a window air conditioner will have a huge impact on how effective it can be, and it’s important that they are fitted at an angle, or you could have serious issues.

This guide will help you understand the best way to fit a window air conditioner and the impact it will have.

How To Tilt A Window AC To Get The Perfect Angle

Most window AC units come with detailed installation instructions, and this will vary depending on the make and model, but here are some steps to get the perfect window AC tilt angle:

  1. .Remove the lower sash of the window
    Remove the lower part of the window where the AC unit will sit.
  2. .Use the extensions to fill the window fully
    Most AC units will come with extensions so you can comfortably fill the space. You may also need to use mounting brackets to support the AC unit unless it sits on the windowsill itself.
  3. .Lift the unit
    Air conditioners can be heavy, and you must handle them carefully, or you can risk injury. You should always try and hold the window air conditioner level, or some elements can move inside. Lift with your knees, and don’t put strain on your back. You may want to ask a friend for help if you’re struggling. Once you lift the unit, you should fit it into the space.
  4. .Tilt the unit
    This is where you need to tilt the unit before you complete the work. AC units should be tilted about half an inch and should not be tilted more than 1 inch, though this may vary depending on the model. Tilting is done by adjusting the metal brackets and angle of the unit in the window.
  5. .Lower the window and seal
    Once your AC unit has been fitted, you need to secure it in place. Ensure the other part of the window is lowered, and use the weatherproof sealant all around the edges. This is often provided by the supplier.

By following these steps and tilting the unit appropriately, you can ensure the moisture stays on the outside and you don’t bring dampness into your home.

How Important Is Having the Right Amount of Tilt?

Having the Right Amount of Tilt

Window air conditioners are fitted directly to windows, and they work by pulling in cold air from the outside to cool your home. They have a simple design but need to be fitted correctly, or they could have an adverse effect on your home.

Window air conditioners need to be tilted to stop any moisture building up in the device or in your home. By tilting the air conditioning unit slightly, you allow the water gathered to be drained outside.

If your air conditioner isn’t tilted, then water can build up in and around your device. This can lead to a lot of moisture being spread throughout your home. This will cause dampness or mold growth from your window AC to damage your belongings.

However, if you tilt your window air conditioner too much, then the oil within the compressor can all gather on one side. This will damage the device and can ultimately cause it to burn out and stop working.

All window air conditioners should be tilted, but only slightly, and it’s all about finding that right balance.

Do’s & Don’ts of Installing a Window AC Yourself

  • Remember to tilt your unit so that moisture can drain outside.
  • Measure your windows before you choose your unit to make sure it fits. Also, make sure you measure the room to get the square footage (by multiplying length and width together). This will indicate how big an AC unit you need.
  • Make sure you can reach an appropriate power source for your AC unit from the window.
  • Attach all mounting rails and side panels. These will help hold your AC unit in place and fill all the gaps around the unit and the window. Make sure you tighten all the screws in place.
  • Assume your windows are suitable. Make sure you assess them thoroughly to see if they can take the load.
  • Don’t lift a heavy AC unit alone. They can weigh over 100 pounds so find a friend to help you.
  • Don’t leave any flaps unsecured. Use the extendable flaps at the side of the AC unit to connect to the side of the window. This will help hold it in place but make sure they are all screwed down and secure.
  • Don’t forget the L brackets. L brackets fit to the bottom of the window and keep it connected to the AC. This prevents anyone from opening the window and the AC unit from falling out.

Installing a Window Air Conditioner in a Tilt (Casement) Window

Tilt windows work differently from standard windows, and it’s a bit more challenging to fit a window AC unit. Below are the steps you need to follow for the main types of tilt window:

Half tilt windows

Only half of these windows open by tilting outwards to let air in. For these, you need to:

  1. .Check the window
    Make sure there is no rot or cracks and that the window is in good condition. Only proceed to the next step if you’re sure the window frame can support the weight of an air conditioner.
  2. .Remove the non-tilt portion of the window
    You’ll need to remove this and replace it with a wood panel. You’ll then be able to drill a hole in the wood to fit the air conditioning unit. Remember, there will be a lot less light in the room after this.
  3. .Slide in the air conditioner sleeve
    Once you’ve drilled an appropriate hole, then you can fit the air conditioner. Remember to tilt the unit to avoid any moisture build-up inside. Once fitted, you should make sure it is all secure and add in extra supports as needed.
  4. .Seal the edges
    Once fitted, caulk the edges where the window and the air conditioner touch, so it’s fully sealed.
Half Tilt Window AC Frame

Vertical tilt windows

These allow the whole window to tilt open rather than just a portion. For these, you’ll need to:

  1.  Remove the window
    Carefully remove the entire glass pane.
  2.  Fit the support bracket
    Screw in the metal support bracket to the window frame. This will be used to support the AC unit, and once fitted, securely lift the unit onto the bracket.
  3.  Close the window
    Close the window and see where the AC unit touches the window and fits. Extend the side panels so that the air conditioner touches the window on all sides and secures it in place so it won’t move.
  4.  Seal the edges
    Once it is fully fitted on all sides, use a weatherproofing sealant to fill gaps around the outside. Please note that the tilting window will no longer be able to open once this is fitted.

The examples above are for traditional window air conditioning units, but manufacturers now have a range of specialist tilt window models. For these, you will need to follow their instructions which will take you through the process.

The video below explains how to fit an air conditioning unit to a tilt window.

People Also Ask (FAQ)

Should a window air conditioner be level?

No, window air conditioners should be tilted to stop moisture from coming into the home and causing dampness.

How do you install a window air conditioner that opens sideways?

Most window air conditioners are designed to be used in windows that open vertically and can’t be used in horizontal opening windows. It’s vital that you never turn your air conditioner to make it fit because they rely on gravity to function correctly. Instead, look for a specialist model that will work in your window.

How do you seal a window air conditioner gap?

For gaps of less than 1/8th inch, you can just use the weatherproofing sealant. Sealing larger gaps requires a piece of weatherproofing and a foam sealant to fully close the gap.

Related Article Best AC Window Sealer Reviews

How do you prop up a window AC?

Window ACs are propped up and supported by the windowsill itself or with brackets fitted to the window.


Air conditioning units are incredibly valuable and give you full environmental control of your surroundings. To get the most from your window AC unit, you need to make sure it’s tilted between 0.5 and 1 inch so that all moisture drains outwards.

So, follow this guide and make sure you’re getting the most from your window air conditioning unit.

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.