New York window heat pump: heating down to minus 22 degrees

In the United States, an unusual heating appliance is causing a stir: it sits in a window, withstands Arctic cold and lowers electricity bills.

While many people in Europe still rely on conventional radiators or bulky split air-conditioning systems, a different approach is gaining ground in New York: a compact air-to-air heat pump fitted like a window air-conditioning unit – but designed for heating, even in freezing sub-zero conditions. Here is the technology behind it, what it could mean for the European market and whether looking across the Atlantic is worthwhile.

How a window heat pump takes on winter

Clattering cast-iron radiators, draughty older buildings and power-hungry electric supplementary heaters are everyday realities in New York. This is precisely where manufacturer Midea is positioning its new window heat pump. The unit is placed into a standard vertically sliding window opening, wedged firmly in position and sealed – and it is ready to operate.

Drilling through walls, arranging installers or setting aside an entire day are unnecessary. Early users report installation times of under an hour, without specialist tools or a professional tradesperson. That is a compelling benefit in densely built-up cities with large numbers of rented flats.

“A heat pump installed like a window unit is ideal for older buildings where wall openings are not permitted or wanted.”

The system is primarily intended for:

• older rental buildings without modern heating technology
• blocks of flats where building services can barely be altered
• urban social housing requiring rapid modernisation
• small flats with no space for outdoor units

That is the central principle: replacing purely electric direct heaters with efficient heat-pump technology, without extensive building work.

Technology in detail: heating down to minus 22 degrees

As an air-to-air heat pump, the appliance draws in outdoor air, extracts thermal energy from it and transfers that heat indoors. Its key feature is a specialised refrigerant circuit combined with a modern inverter compressor, allowing the system to keep operating even in severe frost.

Performance in cold weather

Officially, the system functions at outdoor temperatures down to around minus 25 degrees. According to the data sheet, it still provides practical heating output down to minus 22 degrees:

Outdoor temperature	Usable heating output
-22 °C	around 1.4 kW
8.3 °C	around 2.6 kW

An output of 1.4 kilowatts is sufficient for a well-insulated room or a small studio flat. At milder temperatures, the output rises considerably. The speed-controlled compressor adjusts this automatically.

“Rather than simply being ‘on’ or ‘off’, an inverter compressor continuously adjusts its output – saving electricity and delivering more even heat.”

Because the appliance does not repeatedly run at full output before switching off, energy use falls. Room temperatures fluctuate less, which users generally find more comfortable: the room no longer overheats in short cycles and then cools down again.

Quiet operation despite powerful technology

Noise is a major weakness of many window-mounted units. Midea attempts to address this with a dedicated Silent mode. At its quietest setting, readings are around 29 dB(A), broadly comparable to a soft whisper or the sound level in a very quiet flat.

In standard heating mode, the level increases to around 51 dB(A). However, this remains within a range familiar to many users of split air-conditioning systems or modern ventilation equipment. In a bedroom within a noisy city, this is usually not a deciding drawback – especially as traffic, sirens and neighbours outside are louder anyway.

Heavy weight and blocked windows

Convenience comes at a cost, and not merely a financial one. The window unit weighs around 59 kilograms. Once installed, it permanently blocks most of the window opening. Ventilating the room and cleaning the window become more difficult, while less daylight enters.

Many people in small flats are therefore hesitant. A white box in the only window, which can barely be moved, bothers some people much more than a compact wall-mounted unit in an unobtrusive location.

• high weight: difficult to handle without a second person
• fixed position: the window can only be used to a limited extent
• visual impact on the building façade

This could prove particularly contentious in countries with strict rules governing the exterior appearance of buildings.

The drawback: price and regional limitations

The entry cost is high. Depending on the version, prices currently range from around US$2,800 to US$3,000, excluding subsidies. Housing providers and public authorities are therefore testing the technology in targeted urban pilot schemes, including in Boston and Canadian cities, sometimes with grant support.

“The manufacturer is initially targeting professionals and housing associations, rather than an impulse private purchase from a DIY store.”

Midea hopes that increasing sales will bring costs down. High-volume mass production could move the units into significantly more attractive price ranges in the medium to long term. Until then, the system remains an investment for pilot schemes and urban energy-refurbishment programmes.

Why Europe will have to watch for now

For Germany, Austria and Switzerland, one mundane but decisive issue stands in the way: window design. The appliance is built for vertically sliding sash windows – standard in older American buildings but almost unknown in central Europe.

Tilt-and-turn windows dominate there instead. They cannot simply be “built over from below”, as New York residents do. An identical product therefore cannot be adopted without modification. Countries such as Canada or the United Kingdom, where sliding windows are more widespread, could benefit far sooner.

For German-speaking markets, this means that while the idea may inspire manufacturers, the specific design is unsuitable. Possible alternatives include bespoke frame solutions for tilt-and-turn windows or modular outdoor units integrated into existing balcony doors. It will still take time before such versions reach the market.

What this window heater means for the heat transition

Despite these barriers, the concept demonstrates the possible direction of travel: away from central, slow-reacting heating systems and towards flexible, room-by-room solutions. In cities with large stocks of older buildings, replacing entire heating systems is particularly difficult. A window heat pump offers minimal intervention in the building fabric.

This makes sense for typical applications such as:

• upgrading individual, particularly cold rooms without rebuilding the entire system
• offering tenants a more economical alternative to fan heaters
• covering transitional periods when central heating has not yet been switched on
• reducing peak loads in district-heating areas

Because heat pumps multiply the electrical energy supplied to them, both CO₂ emissions and running costs can ideally fall – provided the electricity mix contains sufficient renewable generation and power prices remain manageable.

What consumers in Europe can already look out for

Even if this particular appliance does not simply appear in local DIY shops, it still offers useful lessons. When buying or planning an air-to-air heat pump, it is worth examining several key figures closely:

• Cold-weather operating range: Down to what sub-zero temperatures does the unit reliably provide heat?
• Modulating compressor: Does the system use inverter technology to reduce electricity consumption?
• Noise levels: How loud is the appliance in typical operating modes?
• Installation effort: Are core-drilled holes, an outdoor unit or structural assessments required?

Anyone investing in a split system or air-to-air heat pump today should ensure that it operates as flexibly as the New York window unit: adjustable output, reasonable noise levels and effective operation below zero.

Looking ahead: possible versions for German-speaking markets

From a technical perspective, there is nothing preventing the development of a similar concept for local window designs. Manufacturers could, for example, create narrow outdoor units integrated into specially adapted frame elements for balcony doors or fixed glazing.

The combination with solar installations on roofs or balconies is particularly interesting. If a small air-to-air heat pump runs on self-generated solar electricity during the day and uses grid power only in the evening, its overall balance improves substantially. Such packages could appeal to owners of urban flats who do not want to, or cannot, replace a large central heating system.

Risks remain at the same time: incorrectly sized units provide too little output in winter, poorly planned installation can transmit noise into neighbouring flats, and overly airtight sealing creates a risk of moisture problems. Anyone considering such systems therefore needs sound advice and should not rely solely on marketing claims.

At first glance, the New York window heat pump seems like a niche product. In reality, it clearly shows how much potential lies in combining simple installation with modern inverter technology – an approach that could also prompt new and unexpected heating solutions in German-speaking markets over the coming years.