How to Install a  Window Heat Pump Like a Pro - DIY Tips

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Window style heat pumps are gradually overtaking window air conditioners with the benefit of heating in winter. It's a logical progression, especially with advances in technology, making everything smaller and easier to self-install.

In this article, we will look at the installation process for a window heat pump, which should take very little time to do with the help of a willing pair of hands.

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What is a window heat pump?

As explained in this article, window heat pumps are devices similar to window type ACs, but instead of only cooling, they also heat. These units are mounted in a window frame where the front end faces the room while the back side outdoors. They are designed to remove the warm air from a room - in the summer, capture the heat (latent energy) from the outside air in winter, and use it for further heating operation.

Window heat pumps are the cheapest option when compared to the central HVAC system or even mini-split option. They are ideal for a single room or an apartment.

What size do I need?

Firstly, you need to accurately size the heat pump for the space you wish to cover. Window style heat pumps are available in different power ratings or capacities.

The heat pump capacity depends on the number of BTUs (British Thermal Units), or how much heat you need to raise the temperature of the water.

Measure the room's floor area to get the total square footage, which will give you a guide for the size of the unit you need. The formula for the area is length X width, so if the room has a rectangular shape where one wall is 12 ft. long and the adjacent wall is 10 ft. long, the room area is 12 X 10=120 sq. ft.

Use this table as an approximate guide:

Room Size (sq. ft.)
150-300 5,000-7,000
300-450 7,000-10,000
450-550 10,000-12,000
800-1000 15,000-18,000
1,300-1,600 22,000-24,000

It's important to avoid under or oversizing the heat pump for your room size. Either choice will cost you money, lead to inefficiencies in the unit's performance, and shorten its life. If you have any doubts, you should check it out with a qualified HVAC professional because what may seem like a great deal could end up costing you a lot of money in the longer term.

So, inform yourself or ask for help.

Before the installation

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Measure up

Once you've matched the unit size to the room size, you need to select the window you wish to use for the installation and measure it carefully. Open the window to the maximum and measure the clear space there. Many window heat pumps need a minimum space of around 13", so make sure you note this size.

Window style heat pumps are not very wide, and they should fit most average window spaces easily with an open, clear width of between 22" and 35". Take your measurements with you to the supplier and double-check before you purchase.

Power needs

Also, check the power requirements for your selected model. Smaller and medium-size units will usually plug into a standard home outlet (3 prongs), but do some research first, especially if you need a larger unit. Depending on the model, these units can use either 115 or 240 V.

You may require an electrician to install a dedicated supply for your new window heat pump, so be prepared. If you get a unit with 115 volts and want to use an existing electrical circuit, make sure there are no other loads on the same circuit - to prevent overloading.

It will be best to select a window close to an outlet, as the heat pumps come with power cords that are approximately 6 feet long.

Note: Manufacturers do not recommend extension cords.

Which one is best?

Check out Energy Star* recommended products and the SEER  ratings for maximum efficiency; there is a useful SEER calculator here, and once you have decided on the model you wish to buy, check around for the best prices. Read online reviews, which will give you valuable information to assist with your buying decision.

It pays to check things like the length of warranty and precisely what it covers. Best to know upfront before something happens.

Let the fun begin

So, you've made your purchase, the unit is ready for installation, and you are keen to get started.

What do you need?

A couple of screwdrivers or a cordless unit with a range of bits, as these units vary in the sizes and types of screws or fixings they supply.


Ensure you check for damage and that all the parts are there, brackets, screws, fixings, seals, etc., before you begin.

Test run & fitting

If everything is in perfect condition with no damage, separate the unit from its cabinet. Carry out a test run with the empty cabinet. Open the window fully and place the cabinet in the space and check the fit and clearances.

Make sure the unit is in the position that suits you. It's usually best to center the heat pump in the space; however, your installation may be different, so place it where it suits you best. Once you are satisfied, bring the cabinet back inside, slide the unit back into place and secure it.

Two pairs of hands are useful at this stage as even though they are small, window heat pumps are heavy, and you may also be working in a restricted space.

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Fix the brackets & curtains

Most of the brackets will already be in place on the cabinet; however, every installation will be slightly different; you may need to fit some modifications to the windowsill to ensure correct levels and secure placement of the heat pump.

Fit any support brackets recommended by the manufacturer and ensure they are secure before removing the cabinet, sliding the heat pump back inside, and fixing it in place.

Fix the self-adhesive sealing strip supplied to the underside of the open window. The lower edge of the window frame will fit tightly against the top of the heat pump when in place and will hold it securely.

In addition, there will be two side pleated 'curtains' like accordions, or side panels, which fill the gaps on either side of the unit in its final position. These side panels should be fitted with screws to each side of the cabinet before finally placing the heat pump in the window. The panels would reduce warm/cold air and pollutants getting into your home.

Installation tips

To support the weight of your new heat pump, make sure that the window is strong and there are no weak spots. If there are, fix them.

With assistance, slide the complete heat pump into place in the window opening and the required position. In the case of the vertical windows, lower the window frame until it presses down on the top of the heat pump cabinet to hold it in place.

Note that the heat pump should tilt downwards a little to the outside to assist with drainage of condensate. Most of the unit's weight will be outside. If the unit is level or tilts inwards, it may leak into the room.

You may need to support the rear of the heat pump to keep it in position; if you have access outside, that will make it easier; however, the window frame pressing down across the top of the heat pump should hold it securely in place.

Extend the curtain panels on either side of the unit to fill the gaps. Secure them in place with screws.

Use a small angle bracket between the lower and upper sash window frames to lock them in position and prevent accidental or deliberate opening.

The last thing to do is plug it in (best not to use an extension cable) and run it up. Check everything is running properly and that heating and cooling modes are working. There will be a remote control, so check it works too.

Make sure to hang onto the manual and guarantee information; you never know when you'll need it.

Proper air circulation is important

Buying the best window heat pump is cool, but did you consider its location and air direction upon installation.

If you buy a large unit to cool and heat several rooms, make sure that recirculated air can reach other rooms as well because if it doesn't, it will cool/heat only one room and have short cycles.

If there are pieces of furniture in front of the heat pump, recirculated air will hit the obstacle and quickly return to the louvers and satisfy the thermostat, without having a chance to reach other room areas.

Note that cabinet louvers must have no obstructions and should provide free air movement.

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Final bits & pieces

There will usually be a foam sealing strip fitted between the upper and lower window frames to insulate the gap and prevent insects from getting inside. If there isn't one supplied, it's a worthwhile investment to cut down on leakage.

The unit should also have one or two brackets to secure it firmly to the windowsill on each side for extra safety.

There may be gaps around the heat pump that require additional sealing or insulation to prevent leaks, which will lower the efficiency of your unit and push running costs up. It is well worth the effort to do it straight away.

How to maintain a window heat pump

After your heat pump was installed correctly and was running for some time, now is the time for maintenance. Two things need to be done to keep the unit running with no issues; keeping both air filters and coils clean, removing any obstacles that can reduce the performance and efficiency.

Common problems

Cold air and poor insulation. Upon installation of the plastic side panels, you will successfully keep bugs and animals away from entering the room, but you will have another problem, especially in winter - the cold air will be coming in. Solution is either to add extra foam insulation or buy insulated accordion-style panels.

No support. Window heat pumps are heavy and they can easily damage your window, especially vinyl type. Use L brackets to support your unit and make the proper weight distribution. It is not safe to leave the unit balance on the window sill with the window closed.

Incorrect tilt. Install the heat pump so collected condensation can properly drain. Check the manufacturer's instructions to see do you have to tilt the unit or not. In general, heat pumps and ACs are designed with channels that allow proper drainage, so no tipping is required.

The heat pump is working hard. Install a heat pump in a window that is not directly exposed to the sun. The better option is to use a window that is facing north and is in the shade.

No outlet nearby. If there is no 3-prong electrical outlet nearby, you might want to hire an electrician to connect the heat pump or buy an extension cord designed for air conditioner and heat pump use.


It's all done and is relatively quick and easy to accomplish, especially with a bit of help to lift it. 

It's a natural progression from the usual window air conditioners, which have been the air coolers of choice for many decades.

Heat pumps at this size with their well-known low running costs, combining efficient heating and cooling in a neat compact unit, make them an obvious choice for single-area air conditioning.

If you are trying to avoid costly pipework and retrofitting ducting in your central HVAC system, a window type heat pump might be the solution if extra power is needed.

Make sure you hang onto the manual and guarantee information; you never know when you'll need it.

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