By late June 2026, companies across Europe were starting work before dawn and setting up cooling stations on building sites. They were doing this because temperatures were climbing toward 40°C (104°F), and the electricity system was feeling the strain, according to Reuters. Heat had been building for weeks, and on 21 June, power forecasters flagged this as a prolonged event, not just a quick spike — an important distinction because it affects how much backup electricity is needed, Reuters reported.

Electricity prices climbed sharply. In the third week of June, the cost of power on the wholesale market jumped above €80 per megawatt-hour — a standard unit of electricity — across most of Europe, according to AleaSoft. Earlier, in late May, German power prices had already spiked 29% in a single day when preliminary heat arrived and winds dropped, Reuters reported on 27 May. The problem is straightforward: when it's hot, everyone runs air conditioners at the same time. When it's hot and still, wind turbines produce less electricity. That collision — peak demand meeting lean supply — is the worst-case situation for a power system relying on renewables.

What the Forecasters Said

Europe's grid operators published an official summer forecast saying electricity supply would be adequate and safe for the season, per the European Commission's statement from 29 May. The Commission welcomed this news. But official forecasts are based on historical patterns and averages. A prolonged 40°C heat wave falls outside that average — it's an outlier — which is why the sharp price spikes in late June deserve attention even though the forecast said things would be fine.

The reason prices spiked so much ties to a supply problem: in 2025, hydroelectric dams generated less water-powered electricity than normal, forcing power stations to burn more natural gas instead. This raised Europe's gas import bill 16%, according to Ember's 2026 electricity review. Hydroelectric dams work like a battery: when demand peaks and wind or solar falls short, operators can release stored water to generate power immediately. Heading into summer with less water in reserve meant the grid had lost one of its most important safety tools.

The Situation in the UK

Britain faced extra pressure. UK household electricity prices were 23% higher than the European average in early 2025, according to House of Commons Library research from 27 May 2026. National Grid, the company running the UK's electricity system, reported its financial results for the year ending March 2026 on 14 May, per company records. Those results now look different in light of summer demand more extreme than usual.

Price increases were not even across Europe: household electricity costs rose in 17 European Union countries in late 2025 compared with 2024, but fell in 10 others. The difference comes down to how each country generates power (coal, gas, nuclear, wind, sun) and how quickly cost spikes reach people's electricity bills.

What Companies Are Doing

The early starts and cooling stations appearing at building sites in late June are temporary fixes. Factories and construction firms are rearranging work schedules to use less electricity during the hottest, most expensive hours. They're not rebuilding the entire power system. But the speed and scale at which this is happening across so many companies and countries suggests it may become standard practice every summer, not just an emergency response.

When large employers shift electricity use away from peak afternoon hours, they reshape demand without needing new power plants — a useful tool for grid operators. If early-morning start times become normal across European factories and construction sites each summer, the grid's load pattern changes in measurable ways.

The critical question is how long the heat lasts. When forecasters say a system is adequate, they assume things will return to normal fairly quickly. A heat wave that runs from late June through July tests the backup reserves much harder than a three-day hot spell, particularly because the transmission lines connecting European countries are also under strain. The €80 price level already hit in late June may not hold.