# Smart Tariff API Rules: What Changes for UK Homes [![David Coleman](/uploads_resolved/images/261/320.webp) Author profile for David Coleman](/authors/david-coleman/ "Author profile for David Coleman")[LinkedIn profile for David Coleman](https://www.linkedin.com/in/david-martyn-coleman/ "LinkedIn profile for David Coleman")[David Coleman](/authors/david-coleman/ "Author profile for David Coleman") Founder & Renewable Energy Author, kilowatts.uk Article # Smart tariff interoperability: how the new API rules could help chargers and heat pumps Published 2026-11-05 19:48:26 Updated 2026-11-05 11:48:35 Great Britain has confirmed Phase 1a tariff API rules. See the November code change, planned February 2027 launch and what appliance owners should check. [ Preferred on Google ](https://www.google.com/preferences/source) ![Illustration of a UK home with rooftop solar panels and a home battery.](/uploads_resolved/images/604/320.webp) ## Home energy decisions and the latest developments Illustration of a home energy system; it does not depict a product or installation announced in this article. *Published 5 November 2026. The announcement was published by DESNZ on 30 October; dates below distinguish the code change from the planned service launch.* Great Britain has confirmed the technical rules for sharing electricity tariff prices in a consistent digital format. The aim is to help services such as smart EV charging and heat-pump controls respond to prices without each supplier and appliance maker having to invent a different connection. That is useful groundwork for home energy automation. It does not mean every charger or heat pump will automatically start following every tariff this month. ## Two dates, with different meanings The [DESNZ decision notice](https://www.gov.uk/government/publications/smart-secure-electricity-systems-sses-tariff-interoperability-code-modifications-for-phase-1a), published on 30 October 2026, says the Retail Energy Code modifications take effect on **6 November 2026**. The planned Phase 1a go-live date is **18 February 2027**. These arrangements apply to England, Scotland and Wales. The earlier date incorporates the final technical requirements into the industry code. The later date is the planned implementation milestone. Neither date should be used on its own to promise that a particular product, supplier or household account will be ready. ## What a tariff API actually does An API is a defined way for one piece of software to request information from another. In this case, the information is tariff pricing. A consistent format helps an energy service interpret prices and pass them to a compatible control system. Phase 1a concerns public tariff information. It should not be confused with permission to read a customer's private account or with a command that remotely controls an appliance. A useful household service still has to combine the right price data with the chosen equipment, settings and permissions. ## What changed in the final specification? The [Retail Energy Code Company's update](https://retailenergycode.co.uk/tariff-interoperability-phase-1a-government-response-and-updated-technical-documents-published/), dated 29 October, describes compressed responses, checks for changed data without downloading it again, corrections to data definitions and permanent references replacing temporary ones. These are implementation details, but they help reduce avoidable differences between systems. For a homeowner, the useful question is whether the service works reliably with the actual tariff and appliance, including after a supplier change. A standards announcement is a reason to ask that question; it is not evidence that every manufacturer's integration has passed testing. ## How this could affect a charging or heating decision A charger can potentially move a flexible charging session into cheaper periods. A heating control has a different constraint: comfort and hot-water needs still matter. The cheapest price interval is not automatically the right time for every household activity. Battery owners also need to consider the value of exporting electricity, charging losses and the limits of their equipment. A price-data standard does not calculate those trade-offs on its own, and it cannot guarantee a saving for a particular home. ## Questions to ask a supplier or equipment provider - Will the service support the relevant Phase 1a tariff data, and from what date? - Which tariff types and specific device models are supported? - What happens if the price feed is unavailable or the household changes supplier? - Can the user override a schedule, set a departure deadline or maintain a comfort limit? - Does the quoted price include any ongoing software subscription? Keep a copy of the compatibility information supplied with a quote. When comparing systems, judge the service that is available and documented today, then treat future integration plans separately. An advertised roadmap can be useful, but it should not carry the same weight as a working feature with clear support terms. Tags: [Electricity tariffs](/tags/electricity-tariffs/ "Electricity tariffs")[Ev charging](/tags/ev-charging/ "Ev charging")[Heat pumps](/tags/heat-pumps/ "Heat pumps")[Smart energy](/tags/smart-energy/ "Smart energy") [ Preferred on Google ](https://www.google.com/preferences/source) Solar comparison ## Compare solar for your property Enter your postcode to assess your roof, compare solar options and get quotes from UK installers. - Free postcode start - Home, business and industrial - RoboMo™ maps your roof ## See which panels fit your roof Choose home, business or industrial, then enter your postcode. RoboMo maps the roof and ranks panel brands by fit. - Home - Business - Industrial UK postcode Fast, free and no obligation to proceed. **1. Postcode** Start the assessment for your property. **2. Pin the roof** Mark the array on the map. **3. 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Free authors can put one followed link to their own site in articles each month. [Write for us](/write-for-us/) [Register or sign in](/login/) ## Frequently Asked Questions ### When do the tariff interoperability rules take effect? DESNZ says the Retail Energy Code modifications take effect on 6 November 2026. The planned Phase 1a go-live is 18 February 2027, a separate implementation milestone. ### Does Phase 1a share my private energy account? Phase 1a concerns public tariff pricing information. It is not the same as granting access to a private customer account or permission to control an appliance. ### Will my EV charger automatically work with every tariff? That has not been established. Check the specific device, tariff, service and implementation date with the supplier or manufacturer before relying on automatic optimisation.