Flexible (Non-Firm) Connection Offer: What It Is and Should You Accept One? (2026 Guide)

Grid Connections9 min readPublished 11 June 2026

A flexible connection offer lets you connect to the grid faster and more cheaply by agreeing to export less at peak constraint periods. Whether you should accept depends on your predicted curtailment level, your revenue model, and whether battery storage can recover losses. For many sites, especially those with low predicted curtailment, it is the right call.

Introduction

If your DNO connection offer says "flexible" or "non-firm," it's natural to wonder whether you've been given a worse deal. When a Distribution Network Operator (DNO), the regional company responsible for delivering electricity from the national grid to homes and businesses, returns a connection quote that includes the word "flexible," it can prompt confusion. Is this a worse deal? A workaround? A trap? In practice, a flexible connection offer is a specific access arrangement with defined trade-offs, and for a significant proportion of renewable energy projects it represents not just the cheapest route to grid, but the only practical one given current queue lengths. This article explains what flexible connections are, how curtailment works, what the regulations now require, and how to think through whether to accept or reject an offer.

What is a flexible connection offer?

A flexible connection offer is a non-firm connection arrangement in which you connect to the grid in exchange for agreeing that your export may be restricted at certain times. Those restrictions apply when the local network is operating close to its capacity limits: the DNO's control systems send an instruction to your site to reduce or temporarily halt export.

The alternative is a firm connection, where the DNO reinforces the network to the point where it can accommodate your full generation capacity at all times, and you are contractually guaranteed that capacity. Firm connections carry no curtailment risk, but they require the DNO (and usually you, either directly or via connection charges) to fund network upgrades that can add months or years to lead times and substantial sums to connection costs.

Flexible connections exist in the space between those two positions: you connect now, at lower cost, but accept some uncertainty about how often and for how long your export will be constrained.

How does curtailment work in practice?

Curtailment under a modern flexible connection is largely automated. UK Power Networks, for example, manages its flexible connections via a Distributed Energy Resources Management System (DERMS), an autonomous software system that monitors grid conditions in real time and sends setpoint instructions to connected generators to keep the network within safe operating limits.

When the DNO issues your connection quotation, they are required to accompany it with a curtailment report. This report uses network analysis to estimate the proportion of the year your site is likely to be curtailed. The estimate is site-specific: it depends on the substation you are connecting to, the existing load and generation on that circuit, and the DNO's modelling assumptions.

Curtailment events are typically triggered during periods of high local generation and low demand, which in solar terms means sunny, low-load periods, often weekend midday hours in spring and summer. Battery storage co-located with your generator can partially recover curtailed energy by charging during constrained periods and exporting later.

If the signalling system fails, your installation must automatically reduce to the agreed Maximum Export Capacity within a defined reaction time (typically 15 seconds, with a maximum of 60 seconds under standard DNO requirements). This fail-safe is built into the connection agreement.

Flexible vs firm connection: what is the difference?

Four broad models of non-firm grid connection are used across the UK: capacity-limited access (you accept a lower than requested export limit), time-limited access (non-firm only during defined periods), dynamic operating envelopes (limits vary in real time based on network conditions), and fully flexible access (the DNO can curtail across a wide range) (Springer Nature, 2025). UK DNOs predominantly use dynamic and fully flexible models, managed via DERMS or Active Network Management (ANM) systems.

The table below summarises the key differences between flexible and firm connections:

	Flexible (non-firm) connection	Firm connection
Upfront cost	Lower - no reinforcement contribution required	Higher - may include reinforcement costs
Lead time	Faster - avoids reinforcement works	Slower - depends on network upgrade programme
Export guarantee	No - curtailment possible at times of constraint	Yes - full capacity available at all times
Who manages constraint	DNO via DERMS/ANM	DNO (constraint removed by reinforcement)
Suitable for	Sites with low predicted curtailment, battery co-location, phased development	Sites where guaranteed export is contractually required

The case for accepting a flexible connection

Accepting a flexible connection makes sense in several scenarios.

Curtailment is predicted to be low. The curtailment report that accompanies your offer is your most important analytical tool. If the estimate shows curtailment for a small proportion of annual generation hours, the revenue loss will typically be outweighed by the saving on connection costs and the value of connecting earlier.

Reinforcement costs are prohibitive. Flexible connections can reduce upfront connection costs by up to 80% compared with reinforcement routes (UK Power Networks, 2024). On a community solar project or a smaller commercial installation, that saving can be the difference between a viable and an unviable business case.

Speed matters. Reinforcement works can take years to deliver and are subject to the DNO's capital programme. A flexible connection can allow you to connect on your own programme. Given that the UK's connection queue stood at approximately 726 GW in July 2024 (Energy Networks Association, 2024), avoiding the reinforcement pathway where possible is a material advantage.

You have battery storage. Pairing battery storage with a solar or wind installation (battery co-location, or solar-plus-storage) can largely neutralise the impact of curtailment. During periods when export is restricted, the battery charges. When the constraint lifts, stored energy exports at market rate. Whether this stacks up depends on the scale of curtailment and the battery economics, but it is a well-established mitigation strategy.

The site is part of a phased development. If you intend to expand capacity later, connecting flexibly now gets you on the network and establishes your connection point. A subsequent application for additional capacity can be assessed in the context of what the network looks like at that time.

When you should think twice

Flexible connections are not appropriate in all circumstances.

Your revenue model depends on guaranteed volumes. Some power purchase agreements (PPAs) include volume guarantees or penalties for underdelivery. If your commercial arrangement requires you to export a defined minimum across a given period, curtailment risk is a contractual problem, not just a financial one. Check your PPA terms carefully before accepting a flexible offer.

Curtailment prediction is high. DNOs use conservative modelling, but a curtailment report projecting significant annual generation loss should prompt careful financial analysis. In areas of severe constraint, where the hosting capacity is already close to its ceiling, curtailment frequency can be material. If the numbers do not work, declining and requesting a firm offer (or exploring reinforcement) is the right course.

The site is in a location with chronic constraint and no near-term reinforcement plan. Some substations are deeply constrained and are not scheduled for reinforcement within the DNO's current investment plan. In these cases, a flexible connection may mean persistent curtailment for the entire project life. Ofgem's connections reforms are beginning to address this, but it remains a live risk in parts of the network.

Investor or lender requirements. Project finance lenders sometimes require a firm connection as a condition of debt. If your project relies on external financing, clarify lender requirements before committing to a flexible offer.

What the regulatory framework says

The rules governing flexible connections were substantially updated following Ofgem's Access and Forward-Looking Charges Significant Code Review (Access SCR), a major regulatory reform process published in May 2022 (Ofgem, 2022).

The resulting code change, DCP404 (implemented from 1 April 2023), standardised and clarified access rights for non-firm connections across the distribution network (Ofgem, 2023). The key provisions are:

DNOs may offer curtailable connections where network reinforcement would otherwise be required.
Curtailment must be measured relative to a defined curtailment limit, providing transparency about the extent of the constraint.
Non-firm arrangements must have end-dates: they cannot be open-ended indefinitely, providing some protection against persistent curtailment without a pathway to firm access.
DNOs must issue a curtailment report alongside any flexible connection quotation.

Ofgem's broader connections reform programme, launched through its Connections End-to-End Review, is ongoing as of 2026 and is expected to further tighten standards, including requiring networks to publish real-time capacity and constraint data (Ofgem, 2026). The direction of travel is toward greater transparency and accountability in how both flexible and firm connections are offered and managed.

What to check before you decide

Before accepting or rejecting a flexible connection offer, work through the following:

Read the curtailment report carefully. What is the estimated annual generation loss? Is it expressed as a percentage or in hours? How was it modelled? Ask the DNO to explain the methodology if it is not clear.
Model your revenue under curtailment. Apply the curtailment estimate to your expected generation profile and calculate the revenue impact. Compare this against the connection cost saving and any additional lead time value.
Check your commercial arrangements. Review your PPA, any grant conditions, and your financing agreements for requirements that would be compromised by non-firm access.
Assess your co-location options. If battery storage is not already in scope, consider whether adding it is viable given the connection offer. The economics shift materially when curtailed energy can be recovered.
Ask about the reinforcement pipeline. Request information about whether the constrained substation is in the DNO's reinforcement programme and, if so, the expected timeline. A flexible connection with a clear transition to firm access in three years is a different proposition from one with no upgrade in sight.
Consider the connection amnesty context. In areas where connection reform is releasing queue capacity, the constraint picture may change materially over the next two to three years. Our tracker article on connection amnesty results sets out where capacity is being released.

How Feasibly can help

The decision to accept a flexible connection offer hinges on site-specific data: the DNO's current capacity position, the existing generation and demand on the relevant feeder, and the likely trajectory of constraint as the network evolves. Gathering this information through manual DNO portals and technical reports typically takes days or weeks.

Feasibly's platform pulls live data directly from DNO heat maps, network capacity datasets, and constraint records, making it possible to assess a site's connection prospects and constraint exposure in minutes. For developers screening a pipeline of sites, or community groups trying to assess whether a local site is worth taking further, understanding the flexible vs firm connection position at the outset avoids wasted cost on options that will not work.

Conclusion

A flexible connection offer is not a consolation prize. For many UK renewable energy sites, particularly those in areas where the distribution network is operating close to capacity, it is the most practical route to connection and can offer substantial savings in cost and time. The decision to accept should be grounded in a careful reading of the curtailment report, a financial model that accounts for generation loss, and a check that your commercial and financing arrangements can accommodate non-firm access.

The regulatory framework has matured significantly since April 2023, and DNOs are now required to provide clearer information about curtailment risk at the point of offer. That transparency, combined with the continued development of DERMS and ANM technology, means flexible connections are increasingly well-understood and manageable instruments rather than unknowns.

What they are not is a substitute for doing the analysis. The curtailment report is your starting point, not your endpoint.

Frequently asked

What is the difference between a flexible connection and a firm connection?

A firm connection guarantees your full export capacity at all times, with the DNO upgrading the network as needed to accommodate your generator. A flexible (non-firm) connection allows you to connect without those upgrades, in exchange for agreeing that your export may be curtailed at times when the local network is constrained. Flexible connections are typically cheaper and faster to obtain, but carry curtailment risk.

How much will a flexible connection reduce my connection costs?

Flexible connections can reduce upfront connection costs by up to 80% compared with routes requiring network reinforcement, according to UK Power Networks (Springer Nature, 2025). The saving depends on the specific reinforcement that would otherwise be required, which varies significantly by location.

Can I convert a flexible connection to a firm connection later?

In principle, yes. If the DNO subsequently reinforces the relevant part of the network, or if your connection falls under an arrangement with a defined end-date following which firm access applies, a transition to firm access is possible. You should ask the DNO at the time of the offer what the pathway to firm access looks like and whether any is planned.

What happens during a curtailment event?

The DNO's control system (typically a DERMS or ANM system) detects a network constraint and sends a setpoint instruction to your inverter or generation management system to reduce or halt export. If the signalling fails, your system must automatically reduce to the agreed Maximum Export Capacity within the reaction time specified in your connection agreement (usually 15 seconds).

Is curtailment compensated?

Under standard flexible connection agreements in Great Britain, curtailment is not compensated by the DNO. This is a key difference from the balancing mechanism at transmission level, where curtailment of large generators may attract compensation. Developers should factor expected curtailment losses into their financial models before accepting a flexible offer.

Sources

Current Sustainable/Renewable Energy Reports (2025). Non-Firm Grid Connections: A Review of Access Types, Mechanisms, and Regulatory Frameworks. https://link.springer.com/article/10.1007/s40518-025-00268-7 Accessed 2026-06-11.
UK Power Networks (2024). Flexible connections. https://www.ukpowernetworks.co.uk/new-electricity-connections/distributed-energy-resources-der-generation/flexible-connections Accessed 2026-06-11.
Energy Networks Association (2024). Connections data. https://www.energynetworks.org/industry/connecting-to-the-connections/connections-data Accessed 2026-06-11.
Office of Gas and Electricity Markets (2022). Access and Forward-Looking Charges Significant Code Review: Decision and Direction. https://www.ofgem.gov.uk/decision/access-and-forward-looking-charges-significant-code-review-decision-and-direction Accessed 2026-06-11.
Office of Gas and Electricity Markets (2023). Decision on DCP404 – Access SCR Changes to Terms of Connection for Curtailable Customers. https://www.ofgem.gov.uk/publications/decision-dcp404-access-scr-changes-terms-connection-curtailable-customers Accessed 2026-06-11.
Office of Gas and Electricity Markets (2026). Connections End-to-End Review: Next Steps. https://www.ofgem.gov.uk/sites/default/files/2025-12/connections-end-to-end-review-next-steps-final.pdf Accessed 2026-06-11.

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