Overview of Window Mounted Air Conditioners with Heat

By | October 10, 2014

Overview of Window Mounted Air Conditioners with Heat
Small window-mounted air conditioning units have been used for years to cool a home when it is hot, but these units now come with the capability to both heats and cool a home.

I have been using a small window-mounted air conditioner to cool a small office I have that is an add-on to my home for some time now. The way the room was built makes it impossible to run a vent from the home’s main central cooling and heating system.

The small unit has worked quite well during the summer, but during the winter, I have had to use space heaters. Recently it stopped working; I did get my money out of it; having bought it seven years ago but needing a replacement, I began to read reviews online.

To my surprise, they have been making small window heat pump units for some time now. This is exactly what I needed a small window unit that can both heat and cool; let me get rid of the space heaters. Also, depending on how efficient the unit is, it will be much cheaper to run than space heaters.

After spending a better part of a day reading reviews on Amazon and advice in forums, this is what I found out and what to look for when buying a window-mounted air conditioning with heat.

Heat Pump vs. Heat Strips
Some window mount units will heat a home using heat strips which are no better than an electric space heater. Heating with a filament that heats up when power is applied, as with space heaters, is inefficient and runs the power used up. A heat pump with a good SEER rating, while more expensive initially, will be cheaper to run long-term.

A heat pump works the same way air conditioning works, only in reverse when heat is needed. It uses a compressor (pump) to cycle refrigerant at different pressures through the unit. A heat pump will use gases such as the refrigerant’s ability to heat and cool at different pressures to give out the wanted temperature. Two fans are used as the refrigerant is cycled; one blows into a home, and one outside blows away. Depending on what is wanted, cold or heat, a heat pump will blow into a home at the desired temperature.

If you already run space heaters during the winter and the power usage doesn’t bother you, then getting the cheaper units that are not heat pumps may work for you. You can tell these units are not heat pumps by the words Supplemental Heating or Heat Strips in the title.

What works for one person might not work for the next person so just be aware of the differences.

How Efficient is the Unit
A SEER rating will tell you how efficiently a unit is; the better the SEER rating, the cheaper it will be to run the unit. The SEER rating will only show the power rating when a unit is in Air Conditioning mode or HEAT Pump mode. The SEER rating won’t apply if it is using heat strips to heat the air.

The old window mount unit I used for years had a SEER rating of 5, which today is laughable. Anything below an 8 SEER rating is not up-to-date with technology. Many units are now 13-17 SEER.

How Big a Unit Do You Need?
How much a unit can cool or heat a home is measured by the BTU of the unit and the square feet it can cool or heat. To get the square feet of a room, simply multiply its width by its length. For example, a 10X10 room would be 100 square feet.

There are calculations you can do to get the exact BTUs you will need to cool or heat a room, but a general rule is that for every 250 square feet, you need 6,000 BTUs of power. Of course, you may need more if a room isn’t well insulated or the weather is extreme.

BTU and Square Feet Sizing Chart
Area To Be Cooled (square feet)—-Capacity Needed (BTUs per hour)
100 up to 150———————————–5,000
150 up to 250———————————–6,000
250 up to 300———————————–7,000
300 up to 350———————————–8,000
350 up to 400———————————–9,000
400 up to 450———————————–10,000
450 up to 550———————————–12,000
550 up to 700———————————–14,000
700 up to 1,000———————————18,000
1,000 up to 1,200——————————-21,000
1,200 up to 1,400——————————-23,000
1,400 up to 1,500——————————-24,000
1,500 up to 2,000——————————-30,000
2,000 up to 2,500——————————-34,000

If you are an electrician, you won’t have to worry about rewiring a room, but if you are not, then be sure the voltages match the outlets the unit will be in, most likely 120 Volts. Some units are 240 Volts which is what an electric clothes dryer uses; most outlets in a home are 120 volts.

There are more options than ever when buying a window-mounted air conditioning unit that can both heat and cool. Even portable units can be moved from room to room as needed. What works for one person may not work for another person.

Category: HVAC how to window mounted air conditioner

About Aaron H. Benetti

Aaron H. Benetti an HVAC technician who has worked in the field since 1991. He began his career as an HVAC installer and later began doing troubleshooting and repairs. Around 2010, he began to write books on HVAC topics, mainly tutorials and how-to information. Currently, Aaron works as an HVAC tech and also writes many articles and posts for websites as well as books and videos on HVAC topics.

12 thoughts on “Overview of Window Mounted Air Conditioners with Heat

  1. Richard Walker

    I bought a new Frigidaire window unit from Lowe’s. This is a heat /air unit. This unit blows cools air during the winter, very little heat if any and it will not cool during the summer. Which part I must replace?

  2. Tom

    Mine works like a charm but it’s a little different than I was used to. Instead of blowing hot air until it heats the cool room to the desired temp, it blows air that’s basically the desired temp. It feel like cool air is blowing, but if I set it for 75, within an hour it’s 75. After that the fan cycles to move the air and test the temp and that feels like cold air blowing too, but it still maintains the 75 degree temp. It can be 40 degrees outside and I can get it to 80 inside (but it never feels like hot air blowing. And it doesn’t run constantly to get there.

    PS, I check the temp against a separate thermometer on the wall.

  3. Charley

    No heat cool air when temperature drops. So dissatisfied with this purchase.

  4. Micah Youmans

    I’m having a problem with mine as well. As soon as it gets like 40 degrees outside, the heater starts blowing cool air. What is the problem? Very upsetting considering we paid almost 500.00

  5. Antonio Wells

    My brand new frigidaire window unit with heater cost
    Cost me over $500 with a warranty and it only keeps
    The room fairly warm it’s more or less not doing
    It’s job what can I do is it some sort of trick like
    Holding two buttons and counting to 10


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