Tariff Interoperability Project
Tariff Interoperability Project
Tariff Interoperability Project
What is the Tariff Interoperability Project?
The Tariff Interoperability Project supports the Department for Energy Security and Net Zero’s (DESNZ) Smart Secure Electricity Systems (SSES) Programme by introducing a standardised approach for electricity Suppliers to make Tariff Pricing Data available in a machine-readable and interoperable format.
The project aims to make it easier for consumers, optimisation services, and Energy Smart Appliances (ESAs), such as electric vehicle chargers, heat pumps, and battery systems, to access and respond to electricity price signals. By improving access to tariff information, the arrangements support consumer-led flexibility, helping consumers optimise energy usage and reduce energy costs.

What is RECCo’s role?
RECCo is supporting DESNZ in delivering Tariff Interoperability through the REC by February 2027. This includes developing and maintaining the Tariff Interoperability arrangements, supporting industry engagement, managing implementation activities, and establishing the governance, assurance and operational frameworks required for ongoing operation.
RECCo is working closely with DESNZ, Ofgem, electricity Suppliers, service providers and industry working groups to support the implementation of the arrangements and readiness for delivery in February 2027.
Why is the project needed?
Consumers are increasingly using services and technologies that optimise electricity use based on price signals, including ESAs, electric vehicle chargers, battery systems, and heat pumps. However, electricity tariff information is often provided in different formats and via different mechanisms, making it difficult for third-party services and devices to access and interpret tariff data across Suppliers consistently.
Tariff Interoperability introduces a common approach for making Tariff Pricing Data available, helping to reduce complexity and improve consistency across the market.
The project will:
- Enable optimisation services and ESAs to access Tariff Pricing Data through a standardised approach;
- Support consumer-led flexibility by helping consumers optimise electricity usage and costs;
- Reduce barriers to interoperability between Suppliers, devices and service providers;
- Promote innovation by making tariff data easier to access and use; and
- Provide a consistent framework for governance, performance monitoring and assurance.
Who will use the service?
The Tariff Interoperability arrangements support a range of market participants involved in consumer-led flexibility and tariff optimisation, including:
- Electricity Suppliers will make Tariff Pricing Data available through a standardised API in accordance with the Retail Energy Code and associated technical specifications.
- Optimisation Services and Third-Party Providers will be able to access Tariff Pricing Data and use it to support services such as automated energy optimisation, tariff analysis and flexibility solutions.
- Energy Smart Appliances, such as electric vehicle chargers, battery systems, and heat pumps, may use information from optimisation services to automatically respond to electricity price signals and optimise energy consumption.
- Consumers will benefit from improved access to flexibility services and tariff optimisation solutions, helping them make better use of available tariffs and potentially reduce energy costs.
How will it benefit the industry?
- Reduce the need for bespoke Supplier integrations with parties that want access to tariff data
- Improve interoperability between Suppliers, optimisation services and Energy Smart Appliances
- Support innovation through easier access to Tariff Pricing Data
- Provide common governance and assurance arrangements through the REC
- Support the development of consumer-led flexibility services across the market
Tariff Interoperability Phase 1a: Government response and updated technical documents published
The Department for Energy Security and Net Zero (DESNZ) has confirmed the final technical requirements for Phase 1a of Tariff Interoperability (TI). These requirements will now be added to the Retail Energy Code (REC). The publication follows a targeted industry consultation held between 27 August and 17 September 2026. Feedback from seven organisations has informed updates to the technical documents ahead of launch.
Published documents:
The Government Response is published alongside three technical annexes, which set out the detailed design for TI Phase 1a implementation.
- Tariff Interoperability: Technical Specification Government Response
- Annex B – TI API Technical Specification: a new REC Category 3 document, hosted on the REC Developer Portal
- Annex C – Energy Market Data Specification (EMDS): new and amended TI market messages and data items
- Annex D – Standards Definition Document: amendments to support the TI message type, market roles and YAML naming conventions
- FAQ
Find out more here.
TI Working Groups
The Tariff Interoperability Working Group (TIWG) and Implementation Working Group (IWG) support the delivery of the Tariff Interoperability arrangements by providing forums for industry engagement, implementation planning and technical collaboration.
Interested in participating?
If your organisation would like to participate in the Implementation Working Group or receive updates on Tariff Interoperability activities, please contact:
Tariff Interoperability Phase 1b: Consultation now open
DESNZ and RECCo are inviting industry views on the proposed arrangements for sharing account-specific tariff information as part of Tariff Interoperability (TI) Phase 1b.
The consultation is open until 18 December 2026 and asks for feedback on the regulatory, design, technical and implementation arrangements needed to deliver Phase 1b under the Smart Secure Electricity Systems (SSES) programme. details of the consultation can be found here:
Help shape the future of Tariff Interoperability: Phase 1b consultation now open
Delivery timeline
Milestone | Timing |
Tariff Interoperability consultation completed | January 2026 |
Government Response and implementation arrangements published | 13 May 2026 |
REC Schedule 35 and Electricity Supply Licence Condition (SLC11C) implemented | 18 May 2026 |
Consultation on Phase 1a – API Technical Specification, EMDS changes and Standards Definition document | Q3 2026 |
Supplier implementation and testing period | 2026 – February 2027 |
Further consultation on Phase 1b arrangements and future API enhancements | Q3 2026 |
Phase 1a Go-Live – Public Tariff Pricing Data | 18 February 2027 |
Phase 1b Go-Live – Consumer Specific Tariff Information (aligned to CCS) | November 2027 |
Phase 2 – Developed and discussed through TIWG | TBC |
Related news
Useful links
- Tariff Interoperability MVP Consultation – Government Response
- Annex A – Electricity Supply Standard Licence Conditions
- Annex B – Retail Energy Code Tariff Interoperability Arrangement Schedule
- Annex C – Tariff Interoperability API Technical Specification
- Annex D – Energy Market Data Specification
- Annex E – Standards Definition Document
Get involved
Are you a supplier, optimiser, or ESA manufacturer? Want to shape the TDS or API standard? Join the Tariff Interoperability Working Group (TIWG) by contacting us at committees@recmanager.co.uk