How do air conditioners work, and what is the effect on the environment?

The need for cooling is quickly increasing, putting strain on both the planet’s electricity grids and the global heatwaves, which are getting longer and more intense. With 2024 the hottest year on record and 2025 not far behind, air conditioning is no longer a luxury for many – it’s a lifeline.

Al Jazeera explores the mechanisms of air conditioning, examines cooling history, and offers practical advice on how to protect your AC and lower energy costs.

How does cooling work?

Air conditioners cool indoor spaces by moving heat from inside your home to the outside using a chemical fluid called a refrigerant. The process begins with the indoor unit heating up the room with cold, low-pressure liquid refrigerant and moving the warm air in. The refrigerant absorbs the heat as the air travels across the coils and evaporates into a gas, cooling the air in the process. A fan then blows the cooled air back into the room.

A compressor raises the pressure and temperature of the now-warm refrigerant before moving to the outdoor unit. The refrigerant transforms into a liquid in the condenser coils by releasing heat into the outside air. The cycle then repeats.

How long have air conditioners been in use?

In 1820, British scientist Michael Faraday discovered that compressing and evaporating ammonia could chill air. The foundation for contemporary refrigeration and cooling systems was made with this early breakthrough.

American physician John Gorrie approached the subject in a practical way in the 1830s. He built a machine in Florida which created ice and used it to cool hospital rooms, aiming to treat patients suffering from tropical diseases.

At a New York printing press, Willis Carrier, an American engineer, created a system to regulate humidity and temperature in the early years of air conditioning. Carrier’s invention is regarded as the first true air conditioner despite its claims to combat humidity, which causes paper to contract, expand, and change in color.

By 1914, the first residential air conditioner was installed in a Minneapolis mansion. It was large, roughly the size of a room, and not very affordable for a typical household.

The first window-mounted cooling unit was created in 1931 by engineers HH Schultz and JQ Sherman to make it easier for each room. This innovation paved the way for household adoption in urban areas.

The 1940s and 1950s saw a rapid expansion in air conditioning use. AC entered homes and offices after World War II thanks to economic growth, mass production, and booms in suburban housing. In this context, toxic refrigerants like ammonia and propane were replaced with Freon (a chlorofluorocarbon, or CFC), making systems safer, smaller, and installation-friendly.

In Japan, the mini-split system was first developed in the late 1950s as a more effective alternative to cumbersome window treatments and central HVAC systems. Its key innovation was a ductless design, which delivers air directly from an outdoor compressor to an indoor air handler – minimising energy loss typically caused by ductwork.

By the 1970s and 1980s, mini-splits had become common in both North America and Asia. Their flexible installation and energy efficiency made them ideal for older buildings where retrofitting ducts was costly or impractical, as well as for homeowners seeking precise, room-by-room climate control. This is when inverter technology, which increases the compressor’s efficiency, was developed.

Governments adopted energy efficiency standards for cooling systems in the 1990s as a result of rising energy costs and growing environmental concerns. In response, manufacturers introduced more efficient compressors, thermostats and system designs to reduce electricity consumption. The Clean Air Act of the United States was amended during this time to eliminate ozone-depleting chlorofluorocarbons (CFCs). Hydrofluorocarbons (HFCs), like R-134a, are now more common. But while HFCs don’t harm the ozone layer, they are potent greenhouse gases which contribute significantly to global warming.

Air conditioners began to incorporate digital controls, motion sensors, and smart thermostats in the 2000s, bringing a new wave of innovation. Automated systems made systems more adaptable and effective, while Wi-Fi connectivity made it possible for users to change temperature settings remotely.

By the 2010s, concerns over global warming and the environmental effects of refrigerants triggered a transition away from hydrofluorocarbons (HFCs). In parts of Asia and Europe, new refrigerants like R-32 and R-290 (propane) are already being used, indicating a shift toward low-emission, climate-friendly cooling.

How to select the ideal air conditioner

Choosing the best-sized air conditioner is essential for keeping your home comfortable and your energy bills under control. Having the right size can save you both money and trouble because an AC is a long-term investment.

A small fan will not work as well as a large room because it won’t be able to cool it at all. On the other hand, an oversized AC may cool the space too quickly without removing enough humidity, leaving the room uncomfortably cold and damp.

Other factors to think about:

• Higher tonnage may be required for sun-exposed rooms.
• Ceiling height: Higher ceilings mean more air to cool.
• More people occupy the building, and more heat is produced.
• Appliances may require additional cooling in rooms with computers, microwaves, or TVs.

How to protect your air conditioner

Air conditioners work extremely hard in the hottest months, and proper maintenance can help reduce energy usage, extend the system’s life, and prevent breakdowns.

How can you ensure that yours runs smoothly:

• Don’t set the thermostat too low
• Keep the air filters clean.
• Give it a break
• Don’t keep turning it on and off
• Keep the shade for the outer unit.

How to cut down on energy used by air conditioners

• Install and set a programmable thermostat
• The thermostat can be raised by about 4 degrees using a ceiling fan.
• Seal any gaps and openings to prevent warm air from entering the room.
• Avoid using heat appliances
• To reduce the heat produced by the sun, open the curtains.
• When using kitchen appliances or taking warm baths, use exhaust fans to expel heat.

How much do air conditioners contribute to global warming?

While air conditioners offer much-needed cooling from the sun, they also significantly contribute to global warming, the issue they’re attempting to solve.

Around 2,100 terawatt-hours (TWh) of electricity were used globally in 2022, according to the International Energy Agency (IEA), which includes air conditioners and electric fans. That’s about 7 percent of total global electricity use, which was roughly 29, 000 TWh. Cooling accounts for nearly 20% of electricity consumption, specifically in buildings.

A cost is associated with this enormous energy demand. The IEA estimates that space cooling was responsible for about 1 billion tonnes of CO₂ emissions in 2022 from electricity use alone – about 2.7 percent of global CO₂ emissions from fossil fuels and industry.

And that’s only the start. Refrigerants, which are potent greenhouse gases used in many AC units, are not included in these figures, which add to the cooling’s impact by increasing the climate footprint.

While air conditioning helps us to be comfortable in a world of rising heat each year, it also risks deepening the climate crisis unless cleaner energy and climate-friendly technologies are adopted.

A cooling system experience a global surge

Air conditioner use is rising due to global warming and the rapid urbanization.

Demand for cooling is rising fastest in tropical and subtropical regions, particularly in urban areas.

Because of the “urban heat island effect,” which is caused by heat being trapped in cities by asphalt and concrete, they heat up more quickly than their neighboring countryside.

By 2018, a country like Japan, the US, and South Korea had almost universal air conditioning, according to the IEA. In contrast, ownership remained low in heat-exposed but lower-income nations such as India and South Africa, where access is limited despite intensifying heatwaves.

Countries with higher incomes and hot climates, such as South Korea and Saudi Arabia, where 63 percent of households have AC units, are more prevalent. In addition, as cooling transitions from a luxury to a basic need, AC ownership is rapidly increasing in emerging economies like Indonesia (20%) and India (13).

How to build a homemade air cooler

Here are some construction instructions for a DIY cooler made of styrofoam, ice, and a fan if you don’t have an air conditioner or are trying to cut energy costs.

Although this won’t help with humidity, it can provide temporary cooling when the day is hot.

Source: Aljazeera