Heat waves affect all types of power generation, not just nuclear

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Nuclear power uses the process of fission to generate high levels of heat to generate steam. The steam then spins the blades of a turbine connected to a generator. After doing this work, the steam is directed into a condenser, where water from an external source cools it back into liquid form and recycles it back to the reactor core.

Most nuclear plants are therefore located beside rivers, lakes, or coastlines. When the water from any of these sources rises above its normal temperature range, its ability to cool and condense the steam is reduced. This, in turn, has the effect of reducing the efficiency of turbine and thus the generation of electricity.

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We shouldn’t think, however, that only thermal plants are impacted. Heat waves have different effects on hydro, wind, and solar power with the same overall result: less electricity, less reliably, and, in the latter two cases, equipment that wears out faster.

Heat waves usually arrive alongside drought. Less rainfall and snowmelt mean less water flowing in rivers and into reservoirs, thus less available to generate power. Output falls—sometimes sharply, as when Sichuan Province in China saw hydropower generation cut in half in 2022. The same has happened to some European rivers in 2026 after three major heat waves in the span of just three months.

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