With absolute heat records broken everywhere in France, the temperature of the globe skyrocketing, a single question arises: how to bring the thermometer back down? The choice seems to be moving towards air conditioners: between 2017 and 2020, the equipment rate of French households almost doubled, going from 14 to 25% [1] . This growth does not seem to be slowing because if already 10 air conditioners are sold per second throughout the world, the IEA predicts a further tripling of the world stock by 2050. But air conditioning means consuming energy, which amounts to emit greenhouse gases, therefore ultimately, to heat up…? So air conditioning, what emissions? what alternatives? We're studying that.
Global stock of air conditioners, 1990-2050
The impact of air conditioning on the climate: When the air conditioning heats up
Air conditioning emits more than 4 million tonnes of CO 2 eq per year in France. This is almost half of the country's air transport emissions [2] and represents the equivalent of the emissions of 400,000 French people. But why does air conditioning emit so much?
To operate, air conditioning uses a significant amount of energy . This consumption is all the greater as the requested temperature is lower than the outside temperature. For example, the energy used for air conditioning in the United States is equivalent to the entire energy consumption of Africa. In France, air conditioning is responsible for 4.5% of greenhouse gas emissions generated by electricity production, or more than 900 thousand tonnes of CO 2 eq .
2 emissions associated with the production of electricity consumed by air conditioning systems in 2020 [3]
But this is not the majority of greenhouse gas emissions from air conditioners; the majority of these emissions are due to refrigerants. These fluids are essential for the operation of machines but are also powerful greenhouse gases and are always partly released into the atmosphere. R-410 for example, widely present in air conditioning equipment, has a global warming power (GWP) more than 2000 times greater than that of CO 2 . ADEME estimates that the losses of these fluids represent more than 3.4 million tonnes of CO 2 eq each year.
Global warming power of refrigerant gases lost by air conditioning systems (teqCO2 – 2020) 3
To this we would still have to add the emissions due to the production of machines, their transport, their installation, their end of life... We therefore probably well exceed 4 million tonnes of CO 2 eq per year and this in a market in strong demand. expansion.
But then, in a country like France where greenhouse gas emissions must be divided by 5 by 2050 [4] , can we do without air conditioners?
Why protect yourself from the heat?
It seems difficult to simply do without cooling. In fact, protecting yourself from the heat has at least 2 major advantages: being more productive and reducing mortality during heat waves .
With the development of air conditioning, mortality during periods of extreme heat decreased sharply in the United States from the 1940s until it was divided by 3 in the 1970s. The importance of cooling during heat waves, in particularly for the elderly, no longer needs to be demonstrated. Beyond mortality, it has been shown that morbidity is also increased by high temperatures for numerous diseases (respiratory, cardiovascular, diabetes, intestines, etc.) [5] .
Productivity to be strongly impacted by temperature. According to a study by the Massachusetts Institute of Technology, it drops by 1.5 points per degree above 15°C. On a global scale, a study shows that productivity decreases with the average temperature of the territory [6] . More heat means less production.
Production per capita as a function of average temperature6
We thus understand how difficult it is to do without cooling as lowering the temperature of our living environment is beneficial for our health and our productivity. But then, how can you cool your interior without raising the temperature of the globe?
Alternatives to air conditioning
Let's focus on 2 applications of air conditioning: the office and the car .
A cooler office
According to ADEME, air conditioning represents around 5% of greenhouse gas emissions from residential or tertiary buildings . An upward trend in this estimate is nevertheless anticipated, due to its strong correlation to global warming on the one hand; the multiplication of urban heat islands on the other hand, with city/rural temperature differentials that can peak at +4°C. In Phoenix (United States), for example, air conditioners are responsible for an increase in outdoor temperatures of around 2°C.
Visualization of temperatures in 2008 for a heatwave night[7]
So how can we reduce temperature, energy bills and greenhouse gas emissions? The equation is not simple but admits some solutions studied in particular by ADEME [8] and OID [9] .
Certain installations make it possible to greatly reduce cooling needs:
- Greening roofs and facades are very effective solutions (the temperature difference can reach 15°C) with numerous co-benefits (well-being, support for biodiversity, air quality, acoustic comfort, etc.) but sometimes costly (750€/m² for installation and 60€/m² for maintenance)
- solar protection ( preferably) has the advantage of being effective and inexpensive (solar filters, sunshades, awnings, reflective glazing, solar films, etc.)
- Certain work can be undertaken to improve the insulation of the building or increase the albedo of the walls and roofs. Thermal renovation work reduces the need for cooling in summer but also for heating in winter.
Several good practices make it possible to simply reduce consumption:
- Turn off the air conditioning when the premises are unoccupied
- Prefer opening windows to air conditioning as much as possible (ventilate the premises in the morning and evening)
- Do not set the air conditioning to a temperature lower than 5°C compared to the outside temperature. Below this, overconsumption increases sharply as does the risk of thermal shock, irritation and headaches.
Ride cool
In the car, reducing the use of air conditioning allows you to reduce the vehicle's greenhouse gas emissions by 15% according to ADEME [10] . Air conditioning actually leads to excess fuel consumption of around 1 L/100km for the most recent vehicles and in particular 2 L/100km in town. So how can you reduce your fuel bill and your carbon footprint at the same time?
In summer, opening the windows in town allows you to cool the cabin without turning on the air conditioning. On the highway, opening the windows slows down the vehicle and therefore results in increased fuel consumption of around 5%. However, using air conditioning causes excess consumption of around 0.4 L/100km [11] . Leaving the windows open would therefore ultimately consume less fuel than using air conditioning.
In any case, a few simple practices can help reduce unnecessary consumption:
- Turn off the air conditioning when it turns on automatically but is not needed
- Do not turn the air conditioning on too high: less than 5° difference with the outside temperature to avoid excessive overconsumption
- Use recirculation mode to breathe less polluted air and consume less energy (deactivate this mode from time to time during long journeys or open the windows)
- Turn on the air conditioning only after a few minutes of windows open when the car has been in the sun
- Turn off the air conditioning 10 minutes before the end of the journey to maintain freshness without unnecessary consumption
How to consume less fuel?
To conclude
Air conditioning represents 4 million tonnes of CO 2 eq per year in France in a rapidly growing market. These emissions are mainly due to leaks of refrigerant gas necessary for their operation but also to their energy consumption. To reduce personal and national emissions by 80% by 2050 and adapt to climate change, it is necessary to rethink cooling. Improving your use of air conditioning by turning it on only when necessary and at a reasonable temperature already allows you to improve your balance sheet. To reduce or even eliminate the need for air conditioning, certain practical measures can be taken such as greening facades and roofs, installing solar protection or thermal renovation. Finally, we will now have to pay more attention to the thermal issues of buildings and cities from their construction so as not to suffer from increasingly significant temperature variations. Ultimately , whether at work, in the car or at home, alternatives exist to save your wallet and the planet!
[1] Ecological Transition Agency (ADEME), Air conditioning: towards reasoned use to limit the impact on the environment , 2021
[2] Ministry of Ecological Transition and Territorial Cohesion, Ministry of Energy Transition, Gaseous emissions linked to air traffic , 2021
[3] ADEME modeling – CODA Strategies
[4] Ministry of Ecological Transition and Territorial Cohesion, Ministry of Energy Transition, National Low-Carbon Strategy (SNBC) , 2021
[5] Bart Ostro, Stephen Rauch, Rochelle Green, Brian Malig, Rupa Basu, The Effects of Temperature and Use of Air Conditioning on Hospitalizations , American Journal of Epidemiology, 2010
[6] William D. Nordhaus, “Geography and macroeconomics: New data and new findings”, Proc Natl Acad Sci US , 2006
[7] Descartes Group, 2009
[8] https://expertises.ademe.fr/professionnels/entreprises/performance-energetique-energies-renouvelables/lenergie-bureaux/dossier/ventilation-climatisation/conseils-agir
[9] Sustainable Real Estate Observatory, Guide to adaptive actions to climate change , 2022
[10] Ecological Transition Agency (ADEME), Automotive air conditioning: Energy and environmental impact , 2020
[11] Ecological Transition Agency (ADEME), Automotive air conditioning: Energy and environmental impact , 2020
