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© 2026 Flex Assure Ltd.
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Flex Assure guidelines for industrial and commercial flexibility service customers
Version 2: Published August 2025
These guidelines are intended as a resource for businesses engaging flexibility service provider(s) to participate in energy flexibility markets.
These guidelines are for general information purposes only. You should not rely upon the information in these guidelines as a basis for making any business, legal or any other decisions.
Whilst we endeavour to keep these guidelines up to date and correct, Flex Assure makes no representations or warranties of any kind, express or implied about the completeness, accuracy, reliability, suitability or availability with respect to the information contained in this document. Any reliance you place on such material is therefore strictly at your own risk.
The need for new sources of flexibility in the energy system presents a wide range of opportunities for energy users of all shapes and sizes to engage with, contribute to and benefit from the transition to a net-zero society. Ofgem (2025) defines energy flexibility as:
"modifying generation and/or consumption patterns in reaction to an external signal (such as a change in price) to provide a service within the energy system"
By engaging in flexibility markets, energy users are paid to turn interruptible processes down or off at times of high demand and low generation -- or conversely, to increase electricity use at times of excess generation -- thereby helping the network operator to balance the electricity system. Thus, energy flexibility offers opportunities for businesses to earn revenue and reduce energy bills, while reducing their carbon footprint and helping to reduce the carbon intensity and improve resilience of the wider energy system.
Typical processes which are turned down or off include lighting, air conditioning, electric heating, pumps, and other non-essential equipment. Participating in DSR is voluntary and is designed not to impact on day to day business operations or comfort. Supermarkets, industrial manufacturers, universities, commercial and public buildings, and hospitals are just some examples of businesses which are providing DSR services.
As energy may not be their primary business, businesses wishing to take advantage of these opportunities can choose to work with flexibility service providers, who specialise in coordinating or aggregating sources of flexibility from individual consumers to more effectively deliver services to the grid and generate revenue for their customers. Flexibility providers have technical and policy expertise, which can help sites fully capture the benefits of flexibility, providing a route to market for those businesses that do not have the time and capital to invest into energy specialisation.
These guidelines are meant to support business energy users in their interactions with flexibility service providers. To this end, this document sets out:
These guidelines have been produced by Flex Assure, with input from flexibility service customers and Scheme Members. Flex Assure is a Code of Conduct and Compliance Scheme that sets standards for flexibility service providers and encourages best practice amongst Scheme Members and in the wider energy flexibility sector.
The Flex Assure Scheme offers business energy users assurance of the service they can expect from flexibility service providers, who are signed up to the Scheme. Members of the Scheme commit to abide by the rules set out in the Code of Conduct, and Flex Assure conducts periodic audits to assess compliance with the Code.
Scheme Members can be identified by the Flex Assure Mark, a mark of trust and integrity. The Members Register, accessible on the Flex Assure website, includes information about all Scheme Members and their status under the Scheme, including audit results.
Flex Assure does not dictate contractual terms between a Flexibility Services Provider and their customers. However, energy flexibility customers may use the Flex Assure Code of Conduct as appropriate, in their dealings with Flexibility Services Providers. An energy flexibility customer may, for example, include in their contractual arrangements with a Flexibility Services Provider, requirements for compliance with the Flex Assure Code of Conduct. Flexibility Services Providers, who are signed up to the Flex Assure Scheme, are periodically audited by Flex Assure to monitor their compliance with the Code.
This section provides a brief introduction to some of the most important energy flexibility services used by NESO to balance supply and demand on the electricity network. Please note, this is not a complete overview and, whilst reasonable endeavours are taken to keep this document up to date, this is a rapidly developing space, and Flex Assure does not guarantee that information is accurate and up-to-date. Further information is available via, for example, NESO and Elexon.
The Balancing Mechanism is one of the National Energy System Operator's (NESO) most important tools for balancing electricity supply and demand in close to real time. This is an ad hoc market with no forward commitments and highly dynamic prices.
The purpose of the BM is to balance supply and demand in every half hourly trading period of the day; where NESO predicts an imbalance between electricity generation and demand for a certain time period, they may accept bids or offers from consumers to increase or decrease generation or consumption.
Previously the BM was only open to licensed generators and licensed suppliers, meaning your electricity supplier would need to be the counterparty responsible for monetising your flexibility in this market.
However, from April 2025, NESO has opened up the BM through Wider Access, allowing pre-qualified flexibility service providers (known in this context as Virtual Lead Parties) to submit and dispatch flexibility into this market without the prerequisite of being the supplier for the site.
The Demand Flexibility Service offers a simple way to earn revenue while supporting the electricity system. By reducing or shifting power use during specific periods when the grid is under strain, participating sites are paid for the flexibility they provide. NESO gives advance notice of each event, so businesses can plan adjustments without disrupting core operations.
Participation can be managed directly or through an aggregator, and no complex equipment or real-time control is required. The service is especially suited to sites with flexible processes, energy storage, or controllable loads. DFS allows businesses to cut costs, demonstrate sustainability leadership, and play an active role in maintaining a reliable, low-carbon energy system.
Reserve services enable NESO to access extra sources of power in case of greater than forecast demand on the transmission system, either in the form of increased generation or demand reduction. See NESO's guidance for further information.
NESO and DNOs use Frequency Response services to maintain system frequency second by second. Frequency is determined (and managed) by the second-by-second balance between system demand and generation. If generation is greater than demand, frequency increases, and if demand is greater than generation, frequency falls. National Grid must maintain a system frequency within 1% of 50Hz.
The Capacity Market exists to ensure sufficient capacity to meet projected levels of future electricity demand. Generators and consumers are paid to guarantee provision, one or four years ahead of delivery, of additional capacity when needed. Visit the ERM Delivery Body website for further information.
NESO used Transmission Network Use of System (TNUoS) fixed charging bands to calculate charges for half hourly metered consumers. Transmission Network Use of System (TNUoS) fixed charging bands are the three half-hour settlement periods of highest demand on the GB electricity transmission system between November and February. By reducing consumption at periods where winter peak electricity demand is forecast, consumers can reduce their transmission network charge. The Triad system has now been replaced by a new system based on a series of fixed 'charging bands'.
DNO & DSO Flexibility Services offer a way to earn payments by helping local electricity networks manage demand and capacity. When a Distribution Network Operator (DNO) or Distribution System Operator (DSO) expects congestion or high electricity usage, participating sites can reduce consumption, shift operations, or export power from on-site generation or storage to help manage local grid constraints. In return, the businesses receive payments for the flexibility delivered.
Flexibility varies by region and is often procured through third-party platforms, creating a diverse and dynamic market for flexibility providers. As the electricity system becomes smarter and more decentralised, DNOs are evolving into DSOs, taking a more active role in real-time management of local supply and demand.
Speak to a flexibility service provider to find out more about which services best suit your business.
It can sometimes be difficult to evaluate offers and bids from different flexibility service providers, and to assess which is the best fit for your organisation or site. Here, we have compiled a list of questions and things to consider, when engaging with one or more flexibility service provider(s). These are just suggestions, and the list is not exhaustive. You should always consider and discuss all matters of relevance to your site and circumstances.
If your asset does not meet the minimum entry threshold for a service, look for information on aggregation options via a flexibility service provider. What requirements are there for aggregating, for example similar technology type, availability, location? Does the aggregator have customers that are able to aggregate with my asset now, or do I have to wait for the portfolio to grow and allow for this opportunity?
Below is an overview of the types of information and data a business energy user may wish to share with flexibility service provider(s), in order to ensure that you receive the best and most accurate offers.
Charlotte Roniger, Scheme Manager