On 12 October 2026 Ofgem opened a call for input titled “Energy price cap: updating the time-of-use methodology”. It is open until 20 November 2026 and asks how the cap should work for tariffs that charge different rates at different times of day.
This is not a price announcement and nothing changes on anyone’s bill today. It matters here for one reason: a plug-in solar kit’s entire saving is the unit rate you avoid paying in the hours it generates.
Why Ofgem is looking at this
The cap was built for a simpler market. In Ofgem’s words, it “was set at a time when there were few time-of-use (ToU) offerings apart from Economy 7 (E7), no half-hourly settlement, and when wholesale prices were less influenced by short-term drivers like weather”.
Market-wide half-hourly settlement changes that: suppliers increasingly face the real cost of each half-hour. Ofgem says that “with the MHHS migration well underway, we expect to see greater diversity in costs across customer types and suppliers as adoption of low carbon technologies and time-of-use tariffs changes customer usage behaviour”, and points to the “10-12 GW of consumer-led flexibility capacity by 2030” estimated by the Clean Flexibility Roadmap. Over 60% of domestic customers are protected by the cap.
How multi-rate tariffs are capped today
Worth understanding, because it is the thing that might change. At present the cap does not set a maximum for each time band. Suppliers “are able to set their rates over different time bands, provided the average of those rates (weighted by demand in each time band) is equal to or below the multi-register cap level”.
In other words, a supplier can make one band very cheap and another dear, so long as the weighted average stays under the cap. Which is exactly how a tariff can offer cheap midday electricity.
The three options
Ofgem stresses the list “is not intended to be exhaustive”. In its own words:
- Option 1 — Simple ToU: “We set a two- or three-band ToU tariff with prescribed unit rates for each time band. This would be the only option for a customer defaulting onto a ToU tariff.”
- Option 2 — Type of use caps: “We set multiple ToU variants based on differentiated demand profiles relating to different LCTs (eg a general ToU cap and a separate EV variant).”
- Option 3 — Tariff specific assessment: Ofgem sets the pricing parameters, and “suppliers could then apply their own demand profile that reflects the group of customers they are designing a tariff for to generate a cap level specific to that group”.
What it means for plug-in solar
A plug-in kit cannot shift when it generates. It makes electricity in the middle of the day and saves you whatever that electricity would have cost. So the price of midday electricity is, for a plug-in owner, the number that decides everything.
- Nothing to do today. This is a call for input, not a decision, and the cap in force is unchanged at 26.32p per kWh until 31 December 2026.
- Option 1 is the one to watch. Prescribed rates for two or three bands would, for the first time, put a regulated price on midday electricity for default time-of-use customers. A high one makes a plug-in kit more valuable; a low one makes it less.
- It would also make the sums more predictable. Today a household on a smart tariff has to dig out its own daytime rate to know what a kit is worth. A prescribed band would remove some of that guesswork.
- None of it affects export. A self-installed kit still cannot get an export tariff from any of the six suppliers we read on 5 October — see the Smart Export Guarantee.
If you are weighing up a kit and are on, or considering, a time-of-use tariff, our new guide works through the arithmetic: plug-in solar and time-of-use tariffs.