Sleepless in a heatwave: Why efficient cooling is becoming essential in UK homes in 2025
Britain is enduring another burst of mid-30s°C heat this August, with heat-health alerts issued for large parts of England. Forecasts also flag more frequent “tropical nights” in the UK, when temperatures don’t fall below 20°C, which are especially disrupting sleep patterns.
Hot nights, poor sleep: what the research shows
- When homes overheat, sleep quality suffers
UK studies show that higher indoor daytime temperatures are associated with more reports of disturbed sleep, while international research finds that warmer nights reduce both sleep duration and quality. The effect is particularly pronounced for older adults and women, who are more vulnerable to heat. - Hotter nights are becoming more common
The Met Office reports that nights with temperatures above 20°C are becoming increasingly common in the UK, intensifying fatigue and reducing next-day performance – effects noticeable even in otherwise healthy people.
UK homes aren’t built for this – and it’s showing
- Overheating is on the rise
A 2025 study, based on experiences in 2022, found that the proportion of UK homes reporting overheating had risen from 18% in 2011 to 80% in 2022. Half of those surveyed said the heat had disrupted their sleep. - Even “efficient” properties can overheat
Airtight, well-insulated properties designed for winter energy efficiency can trap heat during summer if they lack adequate shading and ventilation. Part O* of building regulations aims to limit overheating in new builds, but tackling overheating in existing homes remains the bigger challenge. - One in five homes overheats already
Research from Loughborough University suggests that around 20% of homes are already overheating, creating significant health and wellbeing risks during heatwaves.
Heatwaves and health risk: why sleep matters
- Heat-related deaths are a growing concern in the UK.
The UK Health Security Agency (UKHSA) estimates there were 1,311 deaths linked to the summer heat events of 2024, and over 10,000 heat-related deaths between 2020 and 2024. Quality sleep is not just about comfort – it plays a vital role in staying healthy and safe.
Are fans and quick fixes enough?
Many simple measures, such as night-time ventilation, closing blinds during the day, and using lighter bedding, can help, but they are often not enough during extended hot spells or in noisy, urban areas where windows stay shut at night. External sun-shields and shading can be highly effective at reducing heat gain and are being trialled as affordable, easy-to-install options.
Why air conditioning and heat-pump cooling are rising in Britain
- More households are installing cooling
Air conditioning ownership has risen sharply, reaching around 21% in 2022 compared with just 3% in 2011, according to peer-reviewed research published in 2025. This marks a major change in a country that has traditionally gone without cooling. - Heat pumps can cool, too, offering year-round comfort
Reversible air-to-air heat pumps provide efficient heating in winter and cooling in summer. They are increasingly chosen by energy-conscious buyers as a year-round solution that supports net-zero goals, especially as the electricity grid becomes greener and solar generation peaks when cooling demand is highest.
The sleep case for efficient cooling
When bedroom temperatures rise above 26–27°C, it takes longer to fall asleep and the amount of deep sleep decreases. On hot nights, when temperatures remain above 20°C, many UK homes struggle to cool down without active systems. A properly sized, A-rated split unit or air-to-air heat pump can maintain the ideal 18–20°C range for restorative sleep.
Costs in 2025: what UK households are actually paying
- Higher SEER means lower costs
Modern UK split-system air conditioners and heat-pump systems now commonly achieve SEER ratings of 6+, meaning they deliver over 6 units of cooling per unit of electricity used. - Typical bedroom setup and running costs
A high-efficiency 2.5 kW unit running on a moderate night-cool setting typically costs around 10–20p per hour to operate, which is significantly less than older portable or fixed AC units from only a few years ago. - Targeted use saves more
Running for 4–6 hours overnight in one bedroom costs less than £1 per night during peak summer, while delivering uninterrupted sleep comfort.
Practical steps homeowners can take to keep cool
- Block the sun
Stop heat before it gets inside. Use external shading, sun-shields, or awnings, and keep blinds or curtains closed on sun-facing rooms during the day. - Cool your home overnight
When outdoor temperatures drop, let cooler air in by opening secure night vents or trickle vents. If noise or security is an issue, focus on cooling bedrooms. - Choose the right cooling system
For most bedrooms, a quiet and efficient 2.5 kW SEER 6+ split AC or reversible heat-pump system will keep you comfortable without wasting energy. - Use your system wisely
Pre-cool the room before bedtime, run fan on low / eco mode, you can set temperature to 18–20°C (not 16°C) to avoid energy waste and over-cooling. - Plan for the future
If you’re planning renovations, factor in cross-ventilation, Part O* standards for extensions or new rooms. Consider reflective glass or adding greenery outside to help reduce summer heat build-up.
If you’re not sure which cooling option is best for your home, the Smart Projects team can help. We’ll guide you through your options and design a solution that keeps you cool, saves energy, and adds value to your property. Speak to us today for friendly, expert advice tailored to your needs.
*Part O is a section of the UK Building Regulations that focuses on limiting overheating in new residential buildings.