At a glance
- Catch up: Download the Tariff Interoperability Consultation webinar presentation and watch the recording
- What’s changing: A new, standard way for electricity tariff pricing data to be shared and used across the market
- Why it matters: It removes today’s inconsistent tariff data landscape that blocks automation and slows innovation for Energy Smart Appliances (ESAs)
- Have your say: The consultation is open until 20 January 2026 and is available on the REC Portal, and we’re encouraging your response via the Consultation Proforma to make sure every question is covered
- What’s next: The consultation pack includes an implementation timeline, alongside a proposed go-live in Q1 2027
Download the Consultation Proforma to have your say
What are we changing about access to tariff data, and why now
The policy case is simple: Tariff data isn’t currently available in a consistent, reliable format that is easily accessible, which creates friction for consumers, optimisers, and ESA manufacturers. In practice, this means manual set-up, custom integrations, and a retail energy market that can’t scale flexibility as quickly as it needs to.
DESNZ highlighted the legislative basis, noting that the Energy Act 2023 gives the Secretary of State the power to require suppliers to make tariff data available via an Application Programming Interface (API) in a consistent format, allowing devices and services to automate consumption and support savings and smarter system operation.
What’s in scope, and what comes later
Tariff Interoperability is being delivered in two phases:
- Phase one will require suppliers to make electricity data available for time-of-use tariffs and will go-live in Q1 2027
- Phase two will follow from phase 1 and expands to include suppliers making gas data available and supporting more complex tariff structures, such as block tariffs
The current consultation is limited to phase one, so we’re encouraging stakeholders to focus feedback on this stage.
What the arrangements are designed to do
During the webinar, we set out how the draft arrangements have been developed, and the practical use cases they’re built to support, including scenarios where:
- Customers do (or don’t) know their supplier and tariff name
- Suppliers change or replace tariffs over time
We explained standardisation with safeguards. Suppliers would provide tariff data in a consistent format, with additional protections in place where access extends beyond public tariff information.
Who needs to do what
We covered how responsibilities are split between different user types, as follows:
- Suppliers: Build APIs to the technical specification and meet governance obligations
- Users accessing public tariff data: No registration required
- Users accessing consumer-specific data: Registration and a user agreement are required, with clear expectations around security, permitted use, and compliance
We also clarified the scope. These arrangements apply to domestic electricity suppliers, and some larger non-domestic suppliers, with exemptions (and voluntary opt-in) set out in the draft.
How performance, assurance, and compliance would work
A lot of interest centred on how the arrangements would be monitored in practice. The proposed approach includes:
- A REC Code Manager Monitoring Tool that sends daily API messages to suppliers’ public tariff APIs to check performance against Service Level Agreements, and collect operational metrics
- Supplier reporting requirements set out in the technical specification
- Powers for the REC Code Manager to investigate user compliance for accessing consumer-specific data, including suspension or removal of access where needed
Highlights from the Q&A session
The Q&A focused on the real-world edges that can make or break interoperability:
- Agile tariffs: Confirmed as in scope for phase one (as a form of time-of-use tariff), with DESNZ inviting views on any outliers that don’t fit cleanly via the consultation
- Bespoke vs consumer-specific tariffs: Consumer-specific data is information unique to a customer (for example, identifiers or tariff changes), while bespoke charges are negotiated and not widely available
- Updates and notifications: Users accessing generic tariffs should expect to poll for updates, while webhook-style notifications are reserved for registered users accessing consumer-specific data
- Whether ESAs need to be registered individually: This is at the company level, not device-by-device, and manufacturers can decide whether they need public tariff data or consumer-specific data
What happens next
- The consultation remains open until 20 January 2026. It’s available on the REC Portal, and responses should be submitted using the Consultation Proforma: Download Consultation Proforma to have your say
- Next steps include launching a new Implementation Working Group focused on development and delivery in 2026.
- If you have any questions in the meantime, please contact tariffinteroperability@retailenergycode.co.uk
Stay involved
- Read the Tariff Interoperability Consultation webinar presentation and watch the recording
- Full consultation materials — including the Consultation Proforma, letter, and annexes — are available on our Tariff Interoperability Project web page and on the REC Portal
- Join our Tariff Interoperability Consultation Webinar — 17 December 2025
- At a glance Tariff Interoperability Guide
- Our efforts to introduce a Tariff Interoperability Data Specification
- DESNZ confirms the Retail Energy Code will host new Tariff Data Specification
Your webinar questions answered
Tariff Inclusion & Scope
Q: Will Phase 1 include Agile-style tariffs (as technically, these are Time of Use tariffs but with greater granularity) or are Agile-style tariffs considered as ‘complex’ tariffs destined for Phase 2?
A: Time-of-use tariffs, such as Agile tariffs, will be required to be made available in Phase One (Minimum Viable Product). More complex tariffs, such as Block (where pricing depends on levels of consumption), are out of scope.
Q: As a supplier that provides bespoke tariffs, I expect not to be included in phase 1. However, the definition of bespoke isn’t clear enough to exclude those products offered to micro businesses under licence conditions 7D.1-3, as these could be considered widely available.
A: The consultation invites feedback on the definition of ‘bespoke’ (see Question 2 of the Consultation Proforma). Stakeholders are encouraged to respond if they have concerns with the current drafting.
Q: From what I understand, an Industrial & Commercial supplier (i.e. large non-domestic) will not be obliged to provide bespoke tariffs. The proposal also states they will not be made to share deemed tariffs (if that’s all they have to share). Does this also apply to default tariffs? This is all assuming they have over 100,000 non-Current Transformer sites.
A: Our understanding is that default tariffs apply once the original contract term has expired and are therefore still part of the agreed contract. On that basis, we would expect default tariffs to be within scope. If stakeholders feel this approach is disproportionate, they’re encouraged to respond to the question on the exemption criteria within the consultation (see question 1 of Future default tariffs): “Default tariffs are the deals that consumers move onto once a contract expires or if they have yet to proactively choose a tariff.” A deemed contract occurs when a consumer moves to new premises and doesn’t arrange their own tariff/contract – they’re put onto a deemed contract from the supplier that provided energy for the previous consumer at those premises.
Q: As a supplier that only sells to non-domestic customers, we have a small number of “domestic” end users who are supplied on deemed arrangements following a change of use at a premise that was part of a non-domestic agreement. Will we be exempt in this scenario?
A: Non-domestic-only suppliers who provide to less than 100,000 meter points or those who supply to more than 100,000 meter points but only provide bespoke and deemed contracts will be automatically exempt (see Annex C). However, if a supplier provides electricity to both domestic and non-domestic customers, they will not be considered exempt. We have, however, included a route for suppliers to apply to Ofgem for derogation.
Q: Will the Minimum Viable Product cover occasional events like Sunday-saver sessions or free electricity on Christmas Day?
A: Yes. There are free-text fields in the API specification that allow further details to be added as required.
Q: What is out of scope for non-domestic tariffs?
A: Suppliers with less than 100,000 relevant non-domestic premises and suppliers who only need to make bespoke contract data available will be exempt. Bespoke contract data does not need to be made available; however, it can be made available if a supplier chooses.
Definitions & Terminology
Q: Please clarify the difference between Customer-specific tariff information and bespoke charges, as the terminology is a bit confusing. Is it the case that Customer Specific Tariff Information is not specific to that customer, but is public tariff information requested using the details of the specific customer that’s on that public tariff?
A: Customer-specific tariff Information is unique to that customer (such as MPAN) and allows Registered Tariff Interoperability (RTI) users to be notified of changes that affect optimisation (e.g., tariff or supplier changes). Bespoke charges are defined under the Supply Licence and negotiated individually between the supplier and a non-domestic customer. They’re tailored to individual customer needs and are not widely available on the open market.
Q: What determines whether tariff data is “widely available on the open market”?
A: We understand that some non-domestic suppliers offer the same contract rates to various consumers, similar to those in the domestic market. This definition is designed to capture these contracts.
Registration & User Types
Q: Does an Energy Smart Appliance (ESA) needing tariff data need to register individually?
A: No. Only RTI users need to register (and again, only for access via the consumer’s energy supplier account), and these are companies.
Q: Which user type would apply to ESA manufacturers (heat pump / smart thermostat): TI user or RTI user?
A: It would be their choice. If they need access via the consumer’s energy supplier account, they must register as an RTI user.
Q: Will non-registered users (who only have access to generic supplier tariffs, rather than a consumer-specific tariff) be able to get notifications about tariff updates, revisions, and price updates through some webhook notifications or other mechanisms, or is the expectation that such users constantly poll or fetch the system?
A: Only RTI users can receive update notifications. Non-registered users (TI users) must poll manually for updates.
Access & Confidentiality
Q: TI/RTI will have access to a lot of confidential information. What assurances are there for these parties to cover and prevent the risk of a breach of confidentiality? And if a supplier suffers damages as a result, from whom can they recover? An agreement is only as good as the enforcement of prevention and suitable remedies.
A: RTI users must sign a User Agreement and comply with confidentiality requirements. Access is limited to tariff-related information, as defined in the API specification. Breaches may result in suspension or revocation of access. Other regulatory and legal obligations, such as the General Data Protection Regulation and the Data (Use and Access) Act 2025, still apply.
Q: Will the consent tool be absorbed by the central Consumer Consent Solution? What are the interactions between the two?
A: We’ll continue to track Consumer Consent Solution developments and assess alignment as details evolve.
Data Access & System Design
Q: How are ESAs going to offer “the user’s tariffs” to the customer on their apps? Will they have to poll every supplier to scrape the list of tariffs? Or will they be able to integrate with a single point of contact and get the whole list of tariffs in one go?
A: The APIs will be published on each supplier’s website. There’s no centralised repository under the current TI arrangements. If a TI User wants a consumer to pick their supplier and tariff from a list of options, then polling the supplier’s APIs will be necessary to ensure they have all available options. Alternatively, they could register as an RTI User to save the consumer from having to pick from a list.
Q: How do tariffs interact with flex suppliers? If an ESA needs tariff data to decide if to respond to a Flexibility Service Provider event, how is that handled?
A: This will depend on the Flexibility Service Provider’s consumer proposition. The TI arrangements do not mandate how this integration should work.
Schema Governance
Q: Will there be a set of schema terms for supplier APIs? Or will suppliers be able to set their own schema references? If so, what safeguards will be put in place to prevent changes to these schema references once they are implemented?
A: Yes, schema references (API messages and data items) are defined in the API Technical Specification & Data Catalogue to ensure consistency and are included in the consultation.
