With heatwaves becoming hotter and more frequent, demand for air conditioning is expected to rise significantly. However, if the UK and similar countries respond to hotter summers simply by installing more AC, they risk creating a costly, energy-hungry and more unequal future. But there’s a cooler, smarter way forward.
Colleagues and I have surveyed more than 1,600 households across the UK and found that two-thirds used fans in the summer of 2022, and one in five used air conditioning. The vast majority of those AC units were bought during or after that year’s 40°C heatwave – showing how quickly habits can shift.
In our survey, 80% of UK homes reported overheating in summer 2022, four times more than a decade ago. By the end of this century, the temperature in the UK is predicted to exceed 40°C every few years. It’s no wonder that the same survey found a sevenfold increase in air conditioning in the decade prior to 2022.
Relying heavily on AC might seem like a natural adaptation, but it comes with hidden costs. Cooling requires huge amounts of energy at the exact moments when demand is already high. In 2022 and 2023, the UK had to briefly restart a coal power plant to keep the lights – and the air conditioners – on.
AC also deepens inequalities. For wealthier households, it’s a quick fix. But for others, especially lower socioeconomic groups, it’s a dangerous gap in protection.
Passive cooling first
We already have a template for tackling winter energy demand – “insulation first”. That’s because it’s a lot harder to warm a house than it is to stop heat escaping in the first place.
A similar principle applies in summer – “reduce cooling demand first”.
Hot climate countries like those in southern Europe have had lots of practice and we can learn from them. That means starting with passive cooling measures that reduce the need for mechanical cooling in the first place. These measures include:
- shading and shutters to block sunlight before it enters a building
- natural ventilation to let heat escape in cooler hours
- reflective and light-coloured surfaces to deflect solar radiation
- buildings orientated to minimise heat gain
- trees and green infrastructure to cool neighbourhoods.
Many of these are low-cost, quick to install and long-lasting. In Rome, for example, window shutters are so common you barely notice them, yet they dramatically reduce the need for mechanical cooling.
Once demand is lowered, remaining needs can be met by ACs or reversible heat pumps.
Public behaviour matters too
Adapting our building design is not enough. We must adapt our behaviour too.
In Spain, the hottest hours are for siestas. Outdoor activities are paused, and people are more active in the mornings and evenings. Culturally, they understand that keeping curtains closed during the day and opening windows at night can prevent homes from overheating.
In the UK, heat is still culturally framed as “good weather”. Sunny weekends trigger beach trips, barbecues and more outdoor activity, even when it’s dangerously hot. This mismatch between perception and risk is a major public health challenge.
Even as the climate warms, UK energy policy is still designed for winter, not summer. Energy efficiency programmes often overlook the risk of trapping summer heat inside well-insulated homes. The UK needs to embed overheating risk into housing policy, and needs a clear plan to decarbonise cooling alongside heating.
Public risk communication must also catch up. Early warning systems such as red, amber and yellow warnings are great start, but they’re not enough in a country where many people still see 30°C as perfect picnic weather. We need targeted campaigns to shift mindsets and encourage proactive action before the heat arrives.
The 40°C day in 2022 was a wake-up call. We can answer it with more AC – and more bills, emissions and inequality – or we can 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. Reduce cooling demand first, meet the rest efficiently – and Britain can stay cool without overheating the planet.
