Window heat pumps on an apartment building
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Sustainable comfort, window-sized

Window Heat Pumps Bring Efficiency to Renters and Smaller Spaces

Daren Wang
January 14, 2024

Suddenly, heat pumps are everywhere. From being recommended by the United Nations as a major tool in the fight against climate change to helping dry your clothes more efficiently, they are getting all kinds of attention right now.

But people tend to think that the only way to cool or heat our homes with a heat pump is to use a whole-home system. And unless you are building a new home, that would mean replacing an existing HVAC system. If you don’t own your home or can’t afford that big investment, you’re stuck with a traditional heater or air conditioner. But that’s not true.

Enter the window heat pump. Good for both contemporary and vintage homes, these units are a great option for renters or homeowners who aren’t ready to invest in an entirely new system. The compact units are sized to fit most windows and look like an updated window air conditioner. They offer the same cooling function as an air conditioner, but a window heat pump can be turned into a heater with the flip of a switch and keep your home comfortable much more efficiently and cleanly than an old-fashioned furnace.

So what exactly is a heat pump?

During the summer, it functions like an air conditioner, sending cool air into the room and directing heat outside. However, in the winter, while traditional air conditioners are stowed away, the heat pump pulls double duty as a highly efficient heater, sending waves of warm air into your home.

Whereas traditional heaters generate warmth by burning fuel or sending electricity through a resistor to make it hot, heat pumps warm a room by extracting heat from the external air and transferring it indoors. This method is much more efficient and climate-friendly than electricity-dependent heat-generating alternatives like space heaters.

How does a heat pump work?

A crucial component in this process is the refrigerant, a chemical housed within the heat pump. The refrigerant moves continuously through an evaporator, condenser, compressor, and expansion valve.

As it passes through the expansion valve, the liquid refrigerant expands into a gas and that chemical process drops its temperature. It passes through the evaporator coil, where warm air blows over it and cools. That air is blown into your home, cooling it.

The refrigerant absorbs the warmth of the air that has been blown over it and is then compressed into a high-pressure, high-temperature liquid. That liquid is run through another set of coils, and cool air is circulated across it, cooling the gas again while warming the air. The cycle repeats to maintain the cooling effect in the room.

To provide heating, the cycle is reversed through a reversing valve, extracting heat from the external air and introducing it indoors. And even though it might be cold outside, the compressed refrigerant is even colder and can absorb energy from the warmer outside air.

What’s the best heat pump for me?

Heat pumps are very efficient, so efficiency is a top concern for most buyers. Because heat pumps serve as both a heater and an air conditioner, their efficiency is measured on two scales.

Air conditioning efficiency is measured by its Seasonal Energy Efficiency Ratio (SEER). A higher SEER higher value signifies better efficiency. Many consider a SEER rating of 16 as a good target.

When looking at the heating efficiency of window heat pumps, the focus shifts to the Heating Seasonal Performance Factor (HSPF). An HSPF of 9 or higher is deemed efficient, making heat pumps with this rating an excellent choice. This metric underlines the device's proficiency in providing warmth during colder seasons.

If tracking SEER and HSPF numbers is a little too much for you, the coveted Energy Star certification serves as a valuable guide for energy efficiency. Window air conditioners/heat pumps bearing the Energy Star label are accredited by the United States Environmental Protection Agency, attesting to their energy efficiency and adherence to higher quality standards in manufacturing. Keeping an eye out for these certifications is a great step in selecting window heat pumps that is both well-made and environmentally friendly.

When shopping for a heat pump, finding a climate-friendly and efficient unit is key, but there are a bunch of other factors to consider.  Let’s take a look at the key features that can help tailor you decide which unit works for you:

Heat Pump Size

Ensure the heat pump size corresponds to the room dimensions for optimum performance. A unit too small strains to meet temperature requirements, while an oversized one may lead to excessive energy consumption. British Thermal Unit (BTU) is the industry standard for measuring heat pump size. The right BTU for your home depends on the size of your living space and the climate zone you live in. For more on how to calculate that number, check out this wikiHow page.

Air Filter Options

Consider the types of air filters supported by the window heat pump. Units with washable filters simplify maintenance and are more cost-effective. For allergy sufferers, units with HEPA filters are valuable, blocking out 99.97% of particulates 0.3 microns or larger.

Timer Function

A built-in timer allows convenient scheduling for heat pump activation or deactivation. This feature enhances energy efficiency and can help you fine-tune the system to suit your life. For units with an IR remote control, smart AC controllers can provide precise scheduling.

Ball-Bearing Motor

Look for units equipped with ball-bearing motors for quieter operation. This newer technology ensures less noise and quicker starts, helping you have a more quiet, pleasant cooling or heating experience.

Wi-Fi Compatibility

Many window heat pumps offer Wi-Fi connectivity for remote control through smartphone apps. Even without built-in Wi-Fi, smart AC controllers can make your heat pump smart. These controllers offer advanced features such as week-long schedules, temperature and humidity triggers, geolocation, and usage tracking, providing a comprehensive control solution.

If you are looking for a climate-friendly way to warm or cool your home and aren’t in a position to go with a new whole-home heating and cooling system, the new wave of window heat pumps is a great option.

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