Does MHHS change my bill?
Not directly, as far as published programme material shows. MHHS changes how suppliers and the industry settle electricity use behind the scenes. What you pay depends on your contract, though it could enable new tariffs that reward flexible use. Check your contract and ask your supplier if a charge changes.
Market-wide Half-Hourly Settlement (MHHS) is an industry reform run by Elexon for Ofgem. It moves all electricity customers, not just big sites, onto settlement based on half-hourly readings rather than estimated profiles.
Where it stands
- Meter migrations began on 22 October 2025.
- By mid-June 2026, around a third of metering systems had migrated (over 11.3 million).
- Elexon's plan expected about 80% of meters to have migrated by October 2026.
- Full implementation is planned for May 2027.
Does it change what you pay?
Elexon's own update says nothing about bills changing. It describes the new data as something that could support tariffs that reflect conditions on the grid and reward flexible use. So the honest answer is: your unit rate and standing charge come from your contract, and a fixed-price contract is a fixed-price contract.
What could change in practice
- You may be offered time-of-use or flexible products.
- Estimated bills should become less common if your meter sends data.
- The settlement details held for your meter (such as its profile class) are part of what the reform replaces, so your supplier may tell you about changes to how your supply is registered.
What to check
- Read the contract's change-of-law and pass-through clauses, which control whether the supplier can pass on industry costs. See pass-through vs fixed charges.
- Ask when your meter is due to migrate.
- Keep a note of your last actual reading in case of dispute.
If a supplier calls and says you must pay for MHHS or sign something urgently, be wary and check with your supplier directly.
Who to ask, and what not to worry about
You do not need to apply for MHHS or sign anything to take part: migration is handled between your supplier and the industry. Your contract stays with your supplier, and any complaint about a bill still goes to the supplier first, then to the Energy Ombudsman if you are a micro or small business and the complaint is unresolved after eight weeks or you get a deadlock letter. If your meter is not a smart or half-hourly meter, ask your supplier how it will be settled and whether a meter change is planned. See MHHS in our glossary for the short definition.
Full background: MHHS for business.
A plain-English picture of the change
Today, many small sites' usage is shared out across the day using a standard shape, because their meters only give totals. Under MHHS, the industry uses real half-hourly figures from smart meters instead. Think of it as replacing an estimate of when you used power with a measurement.
Example of what could be offered later
Suppose a supplier offers a cheaper rate for use outside the late-afternoon peak. A gym using 5,000 kWh a month, of which 1,000 kWh could be shifted off-peak, saves 1,000 x the price gap. If the gap were 5p, that is 1,000 x £0.05 = £50 a month. This is a hypothetical to show the arithmetic, not a real offer or price.
Questions for your supplier
- When will my meter be migrated and will there be any downtime?
- Will my profile class or settlement type change?
- Do my contract terms allow any change in charges because of MHHS?
Sources
General information only. Energy prices, rules and supplier terms change; check the latest position with your supplier, Ofgem or the Energy Ombudsman before you act.