Why electricity prices spiked during the 2026 summer heatwaves
About the author and contributor
David Edmonds, Head of Portfolio Pricing for EDF Business & Wholesale Services
David works at the forefront of wholesale energy markets, helping businesses understand the factors that influence energy costs, market volatility and risk. His role spans electricity market dynamics, pricing strategy, whole system costs, weather impacts and the changing realities of operating in an increasingly flexible, low-carbon energy system.
Christopher Dalley, Director of EDF Business & Wholesale Services
Christopher leads the business supporting commercial and industrial customers with energy supply, trading, flexibility, wholesale market services, metering, data and decarbonisation solutions.
Contents
Why did electricity prices spike during the 2026 summer heatwaves?
What caused the electricity system to tighten?
What is an Electricity Margin Notice?
Why were the June and July 2026 EMNs significant?
What do summer EMNs mean for businesses?
Why flexibility is becoming more valuable
How better energy data can support business decisions
What businesses should consider next
Frequently asked questions
Sources
Why did electricity prices spike during the 2026 summer heatwaves?
During the final week of June 2026, Great Britain’s electricity system experienced one of its tightest periods of the summer. Wholesale electricity prices rose sharply, NESO issued an Electricity Margin Notice for the Wednesday evening peak, and a second notice followed later that week. A further EMN was then issued on 9 July during another period of extreme heat.
Despite the headlines, Great Britain was not close to running out of electricity. Instead, these events showed how quickly electricity prices can move when weather conditions tighten the balance between supply and demand. For organisations buying energy, managing flexible assets or planning future energy investments, the heatwaves were a useful reminder that energy risk is no longer just a winter challenge.
What caused the electricity system to tighten?
No single factor caused the tightness. The summer events were the result of several system conditions happening at the same time.
1. High temperatures increased demand for cooling
Hot weather across Great Britain and Europe increased electricity demand as homes, offices and businesses used more cooling equipment.
2. Heat also reduced available generation
Heatwaves can affect parts of the generation system as well as demand. Extremely high temperatures and lower water levels reduced the availability or efficiency of some generation assets.
3. Seasonal maintenance reduced generation availability
Summer has traditionally been a period of lower demand and lower power prices, making it a common time for planned maintenance and refuelling outages at larger generators. This meant there was less spare generation capacity available to respond when hot weather, low wind output and higher demand combined to tighten system margins.
4. Wind output was lower than expected
Wind generation was lower than expected, reducing output from one of Britain’s major sources of electricity at a time when demand was elevated.
5. Solar output naturally declined into the evening peak
Solar generation can be strong through the day, but output declines into the evening. If demand remains high during the evening peak, the system may need additional generation, storage, imports or demand-side flexibility.
6. European market conditions mattered too
Great Britain is connected to neighbouring European electricity markets through interconnectors. When neighbouring markets are also experiencing hot weather and tight conditions, the amount and price of available imports can change quickly.
An Electricity Margin Notice is issued by the National Energy System Operator when forecast operating margins are tighter than expected and additional capacity may be needed.
It is not a warning that power cuts are expected. Instead, it is a market signal that encourages generators, storage operators and demand-side participants to make additional flexibility available where possible.
During the June heatwave, the first notice was issued ahead of the Wednesday evening peak and later withdrawn once system margins improved. The market responded as designed and electricity supplies remained secure throughout.
Historically, Electricity Margin Notices have been associated more with winter periods, when demand is typically higher. The significance of the 2026 events is that they occurred during summer heatwaves.
The first event, on 24 June, was notable because NESO issued an EMN during hot, low-wind conditions and later withdrew the notice once margins improved. A further notice followed on 26 June, and another EMN was issued on 9 July during a further hot spell.
The point for customers is clear: energy risk is becoming less seasonal. Hot, still summer evenings can create tight margins in the same way that cold winter evenings have done historically. That means businesses need to think about flexibility, consumption patterns and market exposure all year round.
The June and July events demonstrated that electricity price volatility is increasingly driven by short-term system conditions, not simply by the season. As renewable generation becomes a larger part of the electricity mix, periods of low wind combined with high demand can create price pressure during summer as well as winter.
For organisations on flexible or indexed energy contracts, that can create short-term price exposure. For those on fixed contracts, it reinforces the importance of understanding future procurement strategy and wider energy risk.
The June heatwave showed that energy risk isn’t simply about average annual prices. The system remained secure, but market conditions changed quickly as weather, available generation and demand combined. Businesses increasingly need good visibility of both their energy contracts and their operational flexibility so they can make informed decisions when conditions change.
Christopher Dalley, Director of EDF Business & Wholesale Services
The heatwaves also showed why flexibility is becoming an increasingly important commercial asset. Flexible electricity demand, battery storage, controllable industrial processes and other responsive assets all become more valuable when the electricity system is tight.
Rather than simply consuming electricity, these assets can respond to market conditions by reducing demand, shifting consumption or providing services that help balance the grid.
Events like this are rarely driven by one issue. They happen when several factors come together over a relatively short period. Low wind, changing demand, generation availability and interconnector flows all influence system margins. When those conditions tighten, assets that can respond quickly become increasingly valuable.
David Edmonds,Head of Portfolio Pricing, EDF Business & Wholesale
Making use of flexibility starts with understanding how electricity is consumed. Many organisations only have visibility of total site consumption, making it difficult to identify which assets could be shifted without affecting operations.
Better metering, asset-level data and energy insights can help organisations identify opportunities to reduce costs, participate in flexibility markets and improve operational resilience. As electricity markets become more dynamic, understanding energy use in greater detail is becoming just as important as understanding energy prices.
The 2026 summer EMNs are a useful prompt for businesses to review how exposed they are to short-term electricity market movements. The system remained secure, but the cost of balancing the system changed quickly.
Does your energy contract match your appetite for market risk?
Organisations on flexible or indexed contracts may be more exposed to short-term volatility. Fixed contracts may provide more price certainty, but businesses still need to understand how future procurement decisions could be affected by changing market conditions.
Do you know where and when your business uses electricity?
Better metering, asset-level data and energy insights can help identify where consumption can be shifted or optimised.
Could your assets create value during tight system periods?
Flexible load, battery storage, controllable processes, EV charging and demand-side response can all become more valuable when the system is tight.
Summer 2026 showed that energy resilience is no longer just about securing supply. It is also about understanding how market conditions change, where flexibility exists across an organisation, and how better data can help businesses respond with confidence.
What is an Electricity Margin Notice?
An Electricity Margin Notice is an operational tool used by the National Energy System Operator when forecast electricity margins are tighter than expected and additional capacity may be needed. It asks market participants to make additional generation, storage or demand-side flexibility available where possible.
Did Great Britain nearly run out of electricity during the 2026 heatwaves?
No. The purpose of an EMN is to increase the system’s safety margin by encouraging additional generation or flexibility into the market. It is not the same as a warning of power cuts.
Why did electricity prices rise during the June 2026 heatwave?
Prices rose because several factors combined: high temperatures increased cooling demand, wind generation was lower than expected, some generation availability was reduced, solar output declined into the evening peak and neighbouring European markets were also experiencing weather-driven pressure.
Why are summer Electricity Margin Notices unusual?
Electricity Margin Notices have historically been more associated with winter periods, when demand is higher. The 2026 summer notices are significant because they show that tight system conditions can also emerge during hot, low-wind summer periods.
What happened on 24 June 2026?
NESO issued an EMN for the Wednesday evening peak period after unusually high temperatures and lower-than-expected generation availability contributed to tighter electricity margins. The notice was later withdrawn once margins improved.
What happened on 26 June 2026?
A further EMN was issued for 26 June, with NESO status reporting showing a system warning for an EMN between 19:00 and 22:00.
What happened on 9 July 2026?
NESO issued another EMN during a further period of extreme heat. Reporting at the time linked the notice to tight evening margins and reduced availability of some generation across Europe.
Why does low wind matter during hot weather?
Wind generation is a major part of the electricity mix, so lower-than-expected output can reduce available generation at the same time as demand rises.
Why does solar power not always prevent evening price spikes?
Solar generation can be strong during the day, but output naturally declines into the evening. If demand remains high during the evening peak, the system may need other sources of generation, storage, imports or demand-side flexibility.
How can businesses reduce exposure to electricity price volatility?
Businesses can review procurement strategy, improve visibility of site-level and asset-level consumption, identify flexible loads and consider technologies such as battery storage, smart EV charging or demand-side flexibility.
- NESO: Energy explained blog - Electricity Margin Notice 24.06.26
- NESO: Summer Outlook 2026
- NESO NETS Status Report - 26 June 2026
- Energy Live News: Extreme heat puts pressure on electricity system with margin warning issued
- Osborne Clarke: NESO issues first-ever summer electricity margin notice for GB
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