What is curtailment? Why it occurs and how energy storage can help
As renewable generation grows, so does the challenge of making full use of all the electricity available. When the grid or demand cannot absorb all this energy, part of the generation may have to be restricted. This is known as curtailment, a phenomenon that is becoming increasingly relevant as the share of renewables rises and one in which energy storage can play a key role.
The expansion of renewable energy is increasing the amount of clean electricity available to the power system. However, not all of this energy can always be used at the time it is generated. When the grid, demand or system conditions do not allow all available electricity to be integrated, part of the output must be restricted. This is known as curtailment.
In this article, we explain what curtailment is, why it occurs, what it means for renewable energy integration and how battery energy storage can help make use of some of that electricity at a later time.
- 01. What is curtailment?
- 02. Why does curtailment occur?
- 03. Why is curtailment becoming more important as renewables grow?
- 04. Renewables, flexibility and storage in figures
- 05. How can a battery help reduce curtailment?
- 06. Storage is not the only solution
- 07. Solarig's role in energy storage
What is curtailment?
Curtailment is the deliberate reduction in the output of a power generation facility that could otherwise generate more energy but is unable to deliver all of that electricity to the system at a particular time.
In the case of renewable energy, this can occur when a solar or wind facility is capable of generating electricity but grid constraints, imbalances between generation and demand, or certain technical conditions prevent all available output from being used.
Curtailment therefore does not mean that the plant has stopped operating or that the solar panels or wind turbines necessarily have a technical problem. It means that the power system is temporarily limiting the amount of energy that can be fed into the grid.
When more energy is available than the system can use
Imagine a solar plant capable of producing 100 units of electricity during a particular hour. If demand and available grid capacity can absorb only 70, the remaining 30 units may have to be curtailed. This difference is a simple example of energy that could be subject to curtailment.
Why does curtailment occur?
There is no single cause. Curtailment can result from different characteristics of the power system and, in practice, may be related to technical constraints, market conditions or a combination of both.
Four common causes of curtailment
When available generation increases and the system does not have sufficient capacity to transport, consume or shift it over time, part of the output may need to be reduced.
Excess generation
More renewable electricity may be generated than the system requires at that moment, particularly during periods of high solar output.
Grid congestion
A transmission line or area of the grid may not have sufficient capacity to transport all the electricity being generated at a particular time.
System conditions
Grid stability, security and operational requirements may make it necessary to temporarily restrict certain sources of generation.
Economic signals
Generation may also be reduced as a result of market conditions or economic incentives to limit output.
International literature generally distinguishes between technical and economic curtailment. The specific causes and the way curtailment is measured depend on the market and methodology used.
Why is curtailment becoming more important as renewables grow?
Solar and wind power share a fundamental characteristic: their output depends on variable natural resources. A photovoltaic plant generates electricity when solar radiation is available, while a wind farm generates when wind conditions are suitable.
As these technologies account for a larger share of the electricity mix, there is a greater likelihood of periods when large volumes of renewable generation coincide with relatively low demand or with a grid that does not yet have sufficient capacity to transport all the electricity available.
The IEA notes that curtailment is becoming more frequent and visible across different markets as solar PV and wind deployment grows. It also highlights that persistent levels of curtailment may indicate shortcomings in system flexibility, infrastructure or planning.
In other words, the challenge is no longer simply to generate more renewable electricity. It is also about ensuring that this electricity is available when and where it is needed.
Renewables, flexibility and storage in figures
The growth of renewable generation is increasing the need for flexibility within the power system. Batteries are one of the technologies capable of responding rapidly to this need.
Sources: European Commission , SolarPower Europe and Red Eléctrica .
How can a battery help mitigate the impact of curtailment?
One of the main advantages of energy storage is that it can separate the time at which electricity is generated from the time at which it is used.
At a solar plant equipped with a BESS (Battery Energy Storage System), the battery can charge during periods of excess generation and subsequently discharge that energy when demand is higher or when system conditions make its delivery more valuable.
In this way, storage can turn some of the electricity that might otherwise have been curtailed into energy that can be used at a later time.
From excess generation to usable energy
The principle is straightforward: when renewable generation exceeds the system's immediate capacity to absorb it, storage can shift part of that energy to another time.
What can storage provide beyond reducing the impact of curtailment?
The value of a battery is not limited to preventing some renewable energy from being curtailed. A BESS can provide a range of flexibility services to the power system.
Grid support
Batteries can respond within seconds to changes in system frequency and voltage, providing balancing services that other technologies cannot deliver with the same speed.
Improved renewable integration
Combining solar and wind facilities with storage can help manage the variability of renewable generation more effectively.
Grid congestion relief
In certain configurations, a storage system located close to generation can help manage power flows and alleviate specific grid constraints.
Batteries are an important tool, but they do not replace grid expansion and modernisation, greater interconnection between markets, demand-side flexibility, improved system planning or more advanced operation. Reducing curtailment requires a combination of solutions tailored to the needs of each power system.
Storage is not the only solution
Addressing curtailment does not mean that every unit of curtailed energy should be recovered by installing batteries. The optimal solution depends on the cause of the issue, its location, grid design and the characteristics of the electricity market.
Expanding and reinforcing transmission and distribution networks can increase the capacity to transport electricity from generation areas to centres of demand. Greater interconnection between markets can enable surplus electricity to be shared more effectively, while demand-side flexibility can shift certain types of consumption towards periods when renewable energy is more readily available.
Storage offers one particular advantage: it can address the timing of electricity supply. When renewable electricity is available now but would be more useful several hours later, a battery can provide a bridge between those two moments.
Solarig's role in energy storage
Solarig develops energy solutions that combine renewable generation and storage to address the power system's growing flexibility requirements.
The company brings together capabilities in the development, construction, operation and maintenance of renewable assets and BESS, with an approach spanning the full lifecycle of energy infrastructure.
This experience enables Solarig to approach storage not simply as a technology that complements renewable generation, but as an asset capable of providing flexibility, optimising operations and improving the integration of solar and wind power into increasingly complex electricity systems.
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Information and data based on publications from the International Energy Agency (IEA) , IRENA , European Commission , SolarPower Europe and Red Eléctrica .
Frequently asked questions about curtailment
What is curtailment?
Curtailment is the deliberate reduction of electricity generation that a facility could otherwise produce but which the system cannot use at a particular time because of grid constraints, operational conditions, imbalances between supply and demand, or other economic or technical factors.
What does curtailment mean in renewable energy?
In renewable energy, curtailment refers to restricting some of the electricity that a solar or wind facility could generate and deliver to the system. This may occur, for example, when renewable generation exceeds demand or when the grid does not have sufficient capacity to transport all the available electricity.
Why does solar curtailment occur?
Solar curtailment may result from grid congestion, excess solar generation at certain times, system stability requirements, or particular economic and market conditions.
How can curtailment be reduced?
Curtailment can be reduced through a combination of measures, including grid reinforcement, greater interconnection, demand-side flexibility, improved system planning and operation, and energy storage.
How can a battery help reduce curtailment?
A battery can absorb electricity during periods of excess generation and deliver it later when it is needed. In this way, it can shift energy over time and make use of some generation that might otherwise have been curtailed.
Is energy storage enough to eliminate curtailment?
Not necessarily. Storage is one of the most important flexibility tools, but it needs to be combined with adequate grid infrastructure, demand-side management, interconnections and other measures suited to the characteristics of each power system.
What is a BESS?
BESS stands for Battery Energy Storage System. These systems store electricity for use at a later time and can also provide a range of flexibility services to the power system.
What role does Solarig play in energy storage?
Solarig develops, builds and operates energy infrastructure and has international experience in the operation and maintenance of battery energy storage systems, as well as integrating renewable generation and BESS into energy solutions.
