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Grid and policy

What happens to excess renewable electricity?

When wind and solar generate more than the network can move, some output is turned down. Here is what actually happens, why it happens, and what storage changes.

Updated
30 July 2026
Reading
6 min
Reviewed
Kettle Energy technical review

The short answer

When generation exceeds what the network can carry to where demand is, the system operator asks some generators to reduce output. This is called curtailment. The electricity is not stored somewhere for later — it is simply not produced. Storage close to demand is one way to use more of it instead.

By Kettle Energy editorial team · Published

How it works
  1. 1Wind and solar output rises, often overnight or midday.
  2. 2Network capacity between generation and demand is finite.
  3. 3Where power cannot be moved, output is reduced.
  4. 4Storage near demand can absorb some of that output instead.

Generation, network capacity and demand rarely peak at the same time.

01

Curtailment, explained without jargon

Curtailment means deliberately reducing the output of a generator that could otherwise be producing. It happens because the transmission and distribution networks have physical limits on how much power they can move at once, and because supply and demand must be balanced second by second.

It is a normal part of running an electricity system, not a fault. But when it happens frequently in the same places, it signals that flexibility — moving demand or storing energy — could be doing useful work.

02

Why it is not simply 'wasted'

It is tempting to describe curtailed generation as wasted electricity that could be given to households. That overstates what is technically true. The electricity is never generated, so it cannot be delivered to a specific home, and no one can honestly claim a given household is running on electricity that would otherwise have been thrown away.

The accurate version is more useful anyway: supply, network capacity and demand do not always line up in time, and shifting demand or storing energy narrows that gap.

03

Where storage helps and where it does not

Storage helps when it is sited where the constraint exists and controlled to charge at the right moments. It does not help if it charges at peak times or sits in the wrong part of the network. That is why control software and siting matter at least as much as the battery itself.

For residents

It explains why electricity can be cheaper and cleaner at some hours than others, and why a battery that charges at the right time can lower what a household pays for the same amount of electricity used.

For housing providers

Constraint patterns vary by region. A pilot should record which hours a battery charged and discharged, so the effect can be evaluated rather than assumed.

Assumptions and limitations

  • Curtailment volumes and causes vary by region, season and network conditions.
  • Kettle does not claim to supply electricity that would otherwise have been curtailed.

Sources

  • Battery storage advice
    Energy Saving Trust, 15 July 2026
  • New proposals to cut bills with community batteries
    Department for Energy Security and Net Zero, 4 June 2026
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Where we are today

Founding pilots are now being developed with UK housing providers. Participation will be arranged through partner organisations and will be subject to property eligibility, resident consent and agreed pilot terms.

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