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Tariff Interoperability — and what it means for you

There’s a quiet change coming to UK energy that will make comparing tariffs fairer and smarter. It’s called Tariff Interoperability. Here’s what it is, in plain English — and how Joulely already does the bit that matters to you.

• What it is. Tariff Interoperability sets a single standard way for energy suppliers to publish their tariff prices — machine-readable, and available to trusted services through a common interface. Today every supplier shows prices differently, which is exactly why whole-of-market comparison is so hard. It’s part of the Government’s Smart Secure Electricity Systems programme and is run through the Retail Energy Code.
• Why it’s happening. As more homes get EVs, heat pumps and batteries, the prize is letting those appliances respond automatically to time-of-use prices — charging when power is cheap and greenest. That only works if tariff prices are published in one consistent, readable format. Tariff Interoperability is the plumbing that makes it possible.
• What’s changing for suppliers. This isn’t a nice-to-have — it’s becoming a licence obligation. From 2026 a new licence condition (SLC11C) and a fresh chapter of the Retail Energy Code require suppliers to publish their prices to a common Tariff Data Specification and serve them through standard APIs, with rules on access and quality. In plain terms: the regulator is forcing the data open, which is a genuinely big shift for an industry where every supplier has done its own thing.
• When it lands. The arrangements enter the Retail Energy Code in May 2026. Public tariff pricing data goes live first, from February 2027; access to your own tariff details (with your consent) follows later in 2027.
• What it means for you. Better, more accurate tariff comparisons, and appliances that can shave money off your bill by using power at the cheapest times — without you having to think about it.

Here’s the thing: the consumer side of all this is exactly what Joulely already does. We price the whole market against your own half-hourly usage — including time-of-use tariffs, across gas and electricity — and tell you the genuinely cheapest deal for your home, ranked purely on price. As the standardised tariff feed goes live, we’re built to plug straight into it, so your comparisons get even more complete and automatic.

Until then, we do the hard part by hand so you don’t have to — free, impartial, and on your real numbers.