With heatwaves becoming more frequent and intense, the demand for air conditioning is expected to surge. However, experts warn that simply installing more AC units could lead to a costly, energy-intensive, and unequal future. Instead, adopting passive cooling strategies offers a smarter and more sustainable alternative.
Rising Temperatures and AC Usage
A survey of over 1,600 UK households conducted by researchers found that two-thirds used fans in the summer of 2022, while one in five used air conditioning. Most of those AC units were purchased during or after that year's 40°C heatwave, highlighting how quickly habits can change. The same survey revealed that 80% of UK homes experienced overheating in summer 2022, a fourfold increase from a decade earlier. By the end of this century, temperatures in the UK are predicted to exceed 40°C every few years, driving a sevenfold increase in AC ownership over the past decade.
The Hidden Costs of Air Conditioning
Relying heavily on AC might seem like a natural response, but it comes with hidden costs. Cooling requires vast amounts of energy at peak demand times. In 2022 and 2023, the UK had to briefly restart a coal power plant to keep the grid stable. AC also deepens inequalities, as wealthier households can afford the quick fix while lower-income groups are left vulnerable.
Passive Cooling First
Just as winter energy demand is tackled with an 'insulation first' approach, summer cooling should prioritise 'reduce cooling demand first.' Hot climate countries like those in southern Europe offer valuable lessons. Passive cooling measures include:
- Shading and shutters to block sunlight before it enters a building
- Natural ventilation to let heat escape during cooler hours
- Reflective and light-coloured surfaces to deflect solar radiation
- Building orientation to minimise heat gain
- Trees and green infrastructure to cool neighbourhoods
Many of these measures are low-cost, quick to install, and long-lasting. In Rome, window shutters are ubiquitous yet dramatically reduce the need for mechanical cooling. Once demand is lowered, remaining needs can be met by efficient ACs or reversible heat pumps.
Adapting Behaviour
Building design alone is insufficient; behaviour must also adapt. In Spain, the hottest hours are reserved for siestas, with outdoor activities paused and people more active in mornings and evenings. Culturally, keeping curtains closed during the day and opening windows at night is standard practice. In the UK, heat is still culturally framed as 'good weather,' leading to beach trips and barbecues even when dangerously hot. This mismatch between perception and risk poses a major public health challenge.
UK energy policy remains focused on winter, often overlooking the risk of trapping summer heat in well-insulated homes. Overheating risk must be embedded into housing policy, with a clear plan to decarbonise cooling alongside heating. Public risk communication also needs improvement. While early warning systems like red, amber, and yellow alerts are helpful, they are insufficient in a country where many still see 30°C as perfect picnic weather. Targeted campaigns are needed to shift mindsets and encourage proactive action before heat arrives.
A Cooler Future
The 40°C day in 2022 was a wake-up call. We can respond with more AC—and higher bills, emissions, and inequality—or redesign our buildings, streets, and routines to work with the climate, not against it. AC will still have a role during extreme heat, but it should be the last resort, not the first instinct. By reducing cooling demand first and meeting remaining needs efficiently, Britain can stay cool without overheating the planet.
