England is already on track for its highest number of heat-related deaths since records began. For households that can’t afford to cool their homes, the price cap increase announced this week makes a dangerous situation worse. And it hits hardest for people on low incomes living in poorly insulated homes, private renters, older people, Disabled people, and families with young children.

At the Centre for Sustainable Energy (CSE), we’ve modelled what it would cost to keep a home safe during summer heat and what happens to fuel poverty numbers if we start counting cooling as a basic energy need. The answer is that fuel poverty rates could rise to 17%, and in a more extreme climate scenario, to as much as 29%. Yet the current definition of fuel poverty doesn’t account for summer cooling at all.

What the new price cap means for those struggling to stay cool

The new price cap marks yet another increase in the maximum price per unit of energy that suppliers can charge. This means that, even assuming their energy consumption stays the same, households will have to pay more for their annual energy bill. 

But energy consumption is not staying the same year-on-year. Summer overheating is likely to create a growing demand for the electricity needed to cool homes to a safe temperature. This means that bills will not only be higher due to the increased cost of energy, but they will also be higher because people are using more electricity across the summer months. 

Not everyone is equally affected. The households likely to need more energy to stay cool are the same households that simply can’t afford this extra cost: households in more vulnerable circumstances on low incomes with high heat exposure. This is most likely to include:

• People in poorly insulated or poorly ventilated homes.
• Private renters with limited control over fabric improvements. 
• People who need a cooler home to stay safe i.e. older people, disabled people and families with young children. 

This also includes households managing energy debt built up over winter, who might already be self-disconnecting. Total debt has now reached £4.79 billion in the first quarter of 2026, with £3.6 billion of this being arrears with no repayment arrangement. Households that are entering summer with an unserviceable debt are unable to afford basic comfort measures like fans. 

Why summer cooling needs should change how we think about and define fuel poverty 

Fuel poverty has traditionally been framed as a winter problem: it’s officially defined as the inability to afford enough energy to heat the home to a reasonable standard. But this concept is becoming increasingly outdated. As summers get hotter, some households also need energy to keep their homes safe during extreme heat. This means the definition of fuel poverty risks overlooking a new form of energy hardship that’s just as dangerous to health: the inability to afford to stay cool. 

At CSE, we’ve modelled the extra energy needed to keep a home cool in summer and looked at how this could affect annual bills. If the fuel poverty definitions were to account for this extra energy needed for cooling, then the total number of people in fuel poverty would rise, and the fuel poverty gap would increase. 

Our headline estimates are: 

• Annual bills and the price cap could rise by up to £140. 
• The fuel poverty rate¹ is likely to rise to 14-17% (LILEE) or 36-38% (10% definition) of English households. 
• The fuel poverty gap² could increase by 13-37%. 

In a more extreme summer climate, the estimates increase: 

• Annual bills and the price cap could rise by up to £740. 
• The fuel poverty rate is likely to rise to 25-29% (LILEE) or 44-52% (10% definition). 
• The fuel poverty gap could increase by 100-195%. 

Why current fuel poverty definitions don’t account for summer risk 

In England, fuel poverty is currently measured using the Low Income Low Energy Efficiency (LILEE) definition. A household is considered fuel poor if it lives in a property with a fuel poverty energy efficiency rating of band D or below, and if its residual income falls below the poverty line after required energy costs are modelled. Prior to this, a household was defined to be in fuel poverty if it needed to spend 10% or more of its income on fuel costs to keep adequately warm. 

Both these definitions use a methodology that models heating requirement based on the need to heat the main living space to 21^oC, with the remaining occupied rooms reaching 18^oC. They make no allowance for cooling an overheated home. 

This trend is likely to get worse as our climate warms. As such, there will be a growing requirement to cool homes to keep them safe.  

Because overheating is increasingly a safety issue. The UK Health Security Agency (UKHSA) has already reported that England is on track for the highest number of heat-related deaths in a year since records began. In a preliminary assessment, it said there were ~2,877 heat-related deaths during the May and June heatwaves, almost double the figure for the whole of last year. This is comparable⁴ to the annual number of excess winter deaths, an issue that triggered the National Institute for Health and Care Excellence (NICE) to develop guidance in 2015 to help protect people from the health risks associated with cold homes⁵. 

To understand how fuel poverty policy could evolve in the UK, we can look to warmer climates like Australia and the US. In Australia, the government tackles summer energy poverty by offering targeted electricity rebates and emergency hardship grants to households that hold pensions or concession cards i.e. typically low-income households or those with a health need⁶. In the US some states offer protection to vulnerable households for non-payment of gas or water services during extreme weather conditions for vulnerable populations. However, it’s been recently reported that these rules are failing to keep pace with our warming⁷. 

The original fuel poverty definitions were created to identify households that could not afford to keep their homes adequately warm and meet their basic energy needs. If we aren’t accounting for the extra energy needed to keep homes cool in summer, then we’re no longer accounting for their basic energy needs.

What’s the potential impact of summer cooling needs? 

There are three important dimensions to this question: 

• What’s a reasonable indoor temperature threshold, and how is this set to make sure our homes are both safe and comfortable? 
• What assumptions do we make about the number of days where cooling is needed and how warm it is outside? 
• What’s the best combination of measures to deliver cooling, and are there co-benefits for winter warmth? 

For the purpose of this initial exercise, we did some basic modelling using the existing fuel poverty temperature thresholds to look at a range of options, from a modest safety-based standard to stronger comfort-based standards. Any future research will need to establish the upper limit of safe temperature within a home. For example, the World Health Organisation recommends maintaining an indoor temperature of between 18^oC and 24^oC. A more complex definition is the Chartered Institution of Building Services Engineers (CIBSE) TM59 assessment of overheating risk in homes which sets a limit of 26^oC for Category I (more thermally sensitive/vulnerable occupants).

We used a simple physics-based building energy model to calculate the figures below for a typical building of 90m² total floor area (more details on the model and assumptions can be found in the Appendix). Rather than look at the optimal set of measures to cool a home, which would require detailed research, we based the figures on a cooling system (e.g. air conditioning unit) operating at a Coefficient of Performance (COP) of 3.5 (i.e. 1 kWh electricity gives 3.5 kWh cooling). We have not looked at the use of fans which offer comfort rather than safety.

Table 1: Estimated impact on annual bills

Scenario	Indicative additional electricity demand (kWh)	Approximate annual cost at 26.32p/kWh
2026 cooling scenario: Living room cooled to 24°C​ (daytime)	150–460	£40–£120
2026 cooling scenario: Living room cooled to 21°C​ (daytime)	230–540	£60–£140
2026 cooling scenario: Living room cooled to 21°C (daytime) and master bedroom cooled to 21°C (overnight)​	260–580	£70–£150
2026 cooling scenario: Living room cooled to 21°C (daytime) and all bedrooms to 18°C (overnight)​	350–680	£90–£180
2026 cooling scenario: Whole house cooled to 21°C (daytime) and all bedrooms to 18°C (overnight)​	950–2090	£250–£550
Extreme future cooling scenario: Whole house cooled to 21°C (daytime) and all bedrooms to 18°C (overnight)​	1450–2820	£380–£740

It’s important to note that these are very basic calculations using a simple physics-based building energy model for a specific building. To get a more accurate estimate, there needs to be more detailed and accurate modelling using tools like the Household Energy Model (which includes cooling demand). However, they illustrate the potential scale of the issue. A modest cooling standard (living room only cooled to 21°C in the daytime) might add around £60 to £140 a year to required energy costs for affected households. In an extreme future cooling scenario (+2°C over 2026 average monthly temperatures) with repeated heatwaves requiring multi-room cooling for long periods over the summer, the additional requirement could plausibly add around £380 to £740 a year at the new capped electricity unit rate. 

How this could change fuel poverty numbers

The most certain impact would be on the depth of fuel poverty. The latest official statistics estimate that 2.36 million households in England were in fuel poverty in 2025 (under the LILEE definition), with an average fuel poverty gap of £379. Table 2 below shows the likely impact on the fuel poverty gap under a 2026 cooling scenario where energy needs increase by £60 to £140, as well as the more extreme scenario which creates an additional need of £380 to £740. 

Table 2: Estimated impact on the fuel poverty gap

Scenario	Annual additional cooling cost	Fuel poverty gap	Percentage increase in fuel poverty gap
Baseline official estimate (2025)	–	£379	–
2026 cooling scenario: Living room cooled to 21°C (daytime)	£60–£140	£429–£519	~13–37%
Extreme future cooling scenario: Whole house cooled to 21°C (daytime) and all bedrooms to 18°C (overnight)	£380–£740	£759–£1,119	~100–195%

To estimate the impact of these additional costs on fuel poverty, we used a model we’ve developed using English Housing Survey data. The latest version published is the 2023 version, which is why the baseline figures below are from 2023.  

• Under the LILEE definition, 11.4% of English households (2.80 million) were in fuel poverty in 2023⁸.  
• Under the 10% definition⁹, 34.1% of English households (8.73 million) were in fuel poverty in 2023. 

We’ve chosen to include both fuel poverty definitions in our analysis because they are both relevant to energy policy. The LILEE definition is the official definition of fuel poverty in England. Because it focuses on energy efficiency and income poverty, it is less sensitive to fuel prices. Scotland, Wales and Northern Ireland use a definition based on a household spending 10% of its income on fuel, which means rates of fuel poverty defined in this way are far more sensitive to fuel costs. Whilst we’ve only modelled the impacts in England, showing both definitions gives a good indication of the likely impacts for the whole of the UK. 

Table 3 and Table 4 show the potential impact of summer cooling need on fuel poverty under two of the modelled scenarios. For example, if bills were to increase by £140 per year due to cooling needs, then fuel poverty would rise to ~17.3% under the LILEE definition and ~38% under the 10% definition. Under the more extreme future cooling scenario, fuel poverty could rise to as much as 25-29% under the LILEE definition and 44-52% under the 10% definition. 

Table 3: Estimated impact on fuel poverty (using the LILEE definition)

Scenario	Fuel poverty rate	Percentage point increase	Additional households in fuel poverty (million)	Total households in fuel poverty (millions)
Baseline (2023)	11.4%	–	–	2.80
2026 cooling scenario: Living room cooled to 21°C (daytime)	~13.8–17.3%	+2.4 to +5.9 pts	~0.6–1.4	~3.4–4.2
Extreme future cooling scenario: Whole house cooled to 21°C (daytime) and all bedrooms to 18°C (overnight)	~24.8–29.2%	+13.4 to +17.8 pts	~3.3–4.4	~6.1–7.2

Table 4: Estimated impact on fuel poverty (using the 10% definition)

Scenario	Fuel poverty rate	Percentage point increase	Additional households in fuel poverty (million)	Total households in fuel poverty (millions)
Baseline (2023)	34.1%	–	–	8.73
2026 cooling scenario: Living room cooled to 21°C (daytime)	36.4–38.3%	+2.3 to +4.2 pts	~0.6–1.1	~9.3–9.8
Extreme future cooling scenario: Whole house cooled to 21°C (daytime) and all bedrooms to 18°C (overnight)	44.4–52.4%	+10.3 to +18.3 pts	~2.6–4.7	~11.3–13.4

Implications for energy policy

The wider policy challenge is that England’s fuel poverty framework currently recognises the energy required to maintain safe temperatures in winter but not the energy required to maintain safe temperatures in summer.  

As the climate warms, that distinction will become increasingly difficult to justify. We will be talking about both excess winter and excess summer deaths. Fuel poverty is no longer solely a question of staying warm in winter; it is increasingly about maintaining healthy, resilient and affordable homes throughout the year. If overheating becomes a recognised energy need, fuel poverty policy, energy affordability support, retrofit programmes and price protection mechanisms will all need to evolve accordingly. 

So, what needs to happen to help make our homes healthy, resilient and affordable?

1. Fuel poverty measurement should recognise safe summer temperatures. The methodology needs to identify a temperature threshold that provides safety alongside reasonable comfort.  
2. Price protection needs to reflect essential cooling demand. If cooling is a necessary health protection, policy should consider whether vulnerable households need targeted bill support, social tariffs or protected blocks of essential electricity use during periods of extreme heat. 
3. Retrofit policy must avoid creating homes that are only safe in the winter. Insulation remains vital, but homes also need ventilation, heat pumps that offer summer cooling, shading, reflective surfaces, external shutters, green infrastructure and designs that reduce overheating without simply adding electrical load. 

Do we need a Safe Homes Plan?

Retrofit policy is a vital part of the picture especially given the government is embarking on a £15bn plan to make our homes warm. Is it missing an opportunity to make our homes safe and our communities more resilient? 

The Warm Home Plan’s approach to area-based retrofit offers a significant opportunity to make our homes safe all year round. As well as this, many of the adaptation measures that are needed to make our homes and communities cooler in the summer aren’t confined to the home. Below are some ideas for measures that could be added to the Warm Homes Plan for all homes, as well as those that could feature in the area-based programmes. The area-based measures also give an opportunity to make our communities more resilient e.g. creating more green spaces in our communities which would also bring co-benefits like improved wellbeing. 

Direct retrofit measures (added to the Warm Homes Plan)

• External shading: shutters, louvres, canopies, awnings and solar-control shading. 
• Reflective window films, solar-control glazing and light-coloured external finishes. 
• Ventilation upgrades, secure purge ventilation and summer-proofing of insulation works. 
• Targeted active cooling for vulnerable households or designated cool rooms. 

Measures that need to be included in an area-based approach

• Domestic shade planting, green roofs, green walls and removal of hard landscaping. 
• Street trees, public-space greening, rain gardens and sustainable urban drainage. 
• Cool spaces in community buildings, including shading, ventilation and where necessary efficient cooling. 
• Overheating advice, behaviour guidance and referral to heat-health support. 

Future research needs

This short thought piece is meant to provoke debate. In a warming climate, both extreme cold and heat present a threat to life and risk overwhelming our National Health Service. But there are several key research questions that need to be answered to enable us to raise the profile of the issue, make informed policy decisions and then implement the right solutions. 

The following are a few that this thought piece has brought to light: 

• What should count as a “safe” indoor summer temperature for fuel poverty measurement purposes? 
• What are the likely scenarios for summer temperatures and how may these vary depending on global concentrations of carbon dioxide? 
• Should summer cooling standards be based on health protection, basic safety, or comfort, and how should these be distinguished? 
• Which households are most exposed to summer fuel poverty because of income, health vulnerability, housing condition, tenure, or location? 
• How much additional electricity demand could be created by different summer cooling standards across different dwelling types? 
• How should fuel poverty definitions account for summer overheating risk, not just winter heating need? 
• What would an overheating allowance do to the incidence and depth of fuel poverty under LILEE and the 10% definition? 
• How sensitive are fuel poverty estimates to assumptions about heatwave frequency, duration, night-time temperatures, and cooling technology efficiency? 
• How should essential cooling demand be reflected in the price cap, social tariffs, or targeted bill support? 
• What is the most appropriate policy balance between passive cooling, fabric retrofit, ventilation, shading, green infrastructure and active cooling? 
• Could retrofit programmes unintentionally increase overheating risk if they focus only on winter warmth and energy efficiency? 
• What dwelling archetypes and geographic areas should be prioritised for overheating and cooling-demand modelling? 
• How can models such as the Household Energy Model be used to produce robust estimates of summer cooling need and affordability impacts? 
• What role should the Warm Homes Plan play in making homes safe and affordable year-round, rather than only warmer in winter? 
• How should policy target support for households where cooling is a health necessity rather than a discretionary use of energy? 
• What are the implications of recognising overheating as an essential energy need for future fuel poverty strategy, retrofit policy and energy affordability policy? 

Appendix

For more information on the models we used to calculate cooling demand and fuel poverty estimates, please see the Appendix below.

Footnotes

1. Numbers are shown for England only. ↩︎
2. The fuel poverty gap is the amount of money by which a fuel-poor household’s energy costs would need to fall for them to no longer be in fuel poverty. ↩︎
3. https://www.metoffice.gov.uk/blog/2026/summer-2026-so-far-a-look-at-the-season-at-the-halfway-point-  ↩︎
4. https://www.gov.uk/government/news/ukhsa-publishes-first-cold-mortality-report  ↩︎
5. https://www.nice.org.uk/guidance/ng6/history  ↩︎
6. https://www.energy.gov.au/energy-bill-relief-fund  ↩︎
7. https://energyprograms.org/wp-content/uploads/2024/07/shutoffprotections.pdf  ↩︎
8. Annual Fuel Poverty Statistics in England, 2025 (2023 data),  https://assets.publishing.service.gov.uk/media/67e51e2cbb6002588a90d5d5/annual-fuel-poverty-statistics-report-2025.pdf ↩︎
9. According to the 2001 Fuel Poverty Strategy, a household was deemed to be in fuel poverty if they spent more than 10% of their income on their fuel costs.  ↩︎