Heat, electricity demand, CO2 emissions and costs. Here is the impact of air conditioning in 25 countries

Installing an air conditioner in the home leads to an average increase in electricity consumption of 36%, according to the most accurate models. A recent international study coordinated by Enrica De Cian (Ca' Foscari University of Venice) together with other researchers from the Euro-Mediterranean Centre on Climate Change (CMCC), Iiasa, ifo Institute and Boston University analyses how the adoption and use of air conditioners are impacting household energy consumption worldwide. On particularly hot days, when temperatures exceed seasonal averages and the 'Cooling Degree Days' index (a climate indicator that estimates the energy requirements for cooling buildings during hot weather) is high, this increase can rise by up to 57%. In many nations, especially those already suffering from extreme heat waves, the air conditioner is no longer a fad, but a health necessity, especially for the elderly, children and vulnerable people. The increase in global temperatures - estimated at more than 1.1°C compared to the pre-industrial era - is prompting more and more households to equip themselves with a cooling system, even in regions that until a few years ago did without one.

However, the study highlights a socio-economic divide: energy consumption for air conditioning varies greatly according to income. Households with high incomes consume an average of 1,436 kWh per year for cooling alone, those with lower incomes stop at around 679 kWh. The discrepancy is not only explained by the ability to purchase the appliance: wealthy households tend to choose more powerful models and use them for longer, covering more rooms and maintaining very low indoor temperatures, even on less hot days. Conversely, those with less money often use older or less efficient air conditioners, and only turn them on during the hottest hours, to keep costs down. There is talk of a 'new form of summer energy poverty': it is no longer a question of not being able to heat the house adequately in winter, but of not being able to afford to keep it livable in summer.

In the United States, where penetration is already very high and homes are large, consumption per family is among the highest in the world, with intensive use generating strong summer peaks; in India, the share of air-conditioned homes is still low but will grow rapidly, pushing electricity demand to levels that will require an increase in generation capacity of up to 29%, with major implications for emissions if energy remains fossilised; China, already with a significant diffusion, will see a less explosive increase in percentage terms but huge in absolute value, given the population, making it strategic to switch to efficient systems and renewable sources; in Europe, on the other hand, penetration starts from lower levels and the overall impact on the grid is lower, but the increase in heat waves is accelerating adoption, especially in southern countries, posing here too the problem of combining comfort, sustainability and reduction of 'cooling poverty'.

The predictions are clear: without targeted action, the phenomenon is set to grow rapidly. Today, 27.5% of the world's homes have an air conditioner. According to the different socio-economic scenarios analysed, this share will rise to 40.7-54.6% by 2050. In terms of consumption, global electricity demand for domestic cooling will increase by almost two to three times current levels: it will rise from current levels to between 976 TWh and 1,393 TWh per year. The environmental consequences are not to be underestimated: additional emissions are estimated at between 670 and 956 million tonnes of CO₂ per year, with a social cost that could range between USD 124 and 177 billion.

A possible way out exists, and it is surprisingly consistent with the problem. Areas with the greatest solar potential also tend to be those where cooling demand is most sensitive to energy costs. In other words, installing photovoltaic panels could significantly reduce the economic and environmental impact of air conditioners, because solar energy production coincides with peak usage times. This synergy could be one of the keys to meeting the challenge: not to eliminate comfort - which for many is now a necessity - but to make it sustainable. The risk is that a vicious circle is created: the warmer the climate, the greater the demand for cooling, which in turn, if fuelled by fossil fuels, contributes to global warming.