If your business has had an email or letter from its electricity supplier about “MHHS”, you are not alone. Every supplier is sending them. They usually say that a change is happening, that the supplier will take care of it, and that you do not need to do anything.
That is broadly true. But the messages rarely explain what is actually changing, or why it might matter to you. This guide does that, without the jargon. It is general information, it reflects our understanding at the time of writing, and some of the dates could still move.
MHHS in one sentence
MHHS stands for Market-wide Half-Hourly Settlement. In simple terms, it means that by May 2027 the electricity industry will work out how much electricity every business and home in Great Britain uses in each half hour of the day, using real meter readings wherever possible, instead of relying on averages.
Why half hours matter
Electricity does not cost the same all day. Wholesale prices are typically highest on weekday late afternoons and early evenings, when the whole country is using the most, and lower overnight or when there is plenty of wind and sunshine.
Behind the scenes, the industry adds up how much electricity each supplier’s customers used in every half hour, so that each supplier pays the right amount for the electricity its customers took. This adding-up process is called “settlement”. It is not your bill, and you never see it. But the costs it produces for your supplier feed into the prices you are offered.
How it works today
- Larger sites usually have meters that already record usage every half hour. These sites have been settled on their real half-hourly usage for some years.
- Most smaller businesses have meters that only record a running total. Because nobody knows exactly when that electricity was used, the industry fills the gap with an average daily pattern for “a typical small business”, based on a sample of around 2,500 homes and businesses across the country.
So a café that is busiest in the evening and an office that runs nine to five can be treated as if they used electricity in exactly the same way. The sums also take a long time to finalise: up to 14 months after the electricity was used.
What is changing
- Real usage instead of averages. Smart and half-hourly meters already record usage every half hour. Under MHHS, that real data will be used for every site that has it. Where it is not available, a new estimating method fills the gaps.
- Quicker sums. The 14-month wait for the final figures is due to drop to seven months from April 2027, and then to four months from July 2027.
- Some new names and labels. The companies that read and look after meters are getting new titles, and some details on bills, quotes and contracts may look different.
Why it is happening
Ofgem, the energy regulator, decided on this change in 2021. It estimated that it would save energy customers in Great Britain between about £1.6 billion and £4.5 billion overall between 2021 and 2045.
The idea is simple. Once suppliers are charged for when their customers use electricity, not just how much, they have a reason to reward customers who use it at cheaper times. That should make it easier to offer tariffs with cheaper off-peak prices, and to make the most of batteries, electric vehicle charging and the growing amount of wind and solar power.
When it is happening
| When | What happens |
|---|---|
| October 2025 | Suppliers started moving meters over |
| August 2026 | Around 60% of meters had been moved, according to industry figures |
| 1 April 2027 | Final figures due within seven months instead of 14 |
| 7 May 2027 | Deadline for every meter to be moved |
| 2 July 2027 | The quicker four-month timetable starts |
Your supplier decides when your own sites move, and should tell you when it happens.
What you might notice
For most businesses the move happens in the background. You might see:
- bills, quotes or contracts laid out a little differently
- some new terms in letters from your supplier
- some codes on your bill changing. The main supply number on your electricity bill, known as the MPAN, is not expected to change.
If you have a larger site with a half-hourly meter, you may also be asked to choose which company reads and looks after the meter, or to let your supplier choose for you. Most businesses let the supplier do it.
Will my bill go up?
Not simply because your meter is moved over. The price you pay is set by your supply contract, and the move does not change that by itself.
Over time, though, our view is that when you use electricity is likely to matter more to the price you are offered, not just how much you use. A business that uses a lot at peak times, such as weekday late afternoons and early evenings, may find it costs more to supply. A business that uses more overnight, or evenly through the day, could benefit. This is a general direction, not a prediction for any particular business.
It is also worth knowing what your contract says about costs from industry changes like this one. Some contracts let the supplier pass certain costs on; others fix them for the length of the contract.
Do I need to do anything?
For most businesses, no. Your supplier will move your meters over. A few simple habits will help:
- Read your supplier’s letters about MHHS rather than filing them, and reply if they ask you to confirm anything about your meter.
- Check your first bills after the move. Make sure the details and the amount of electricity used look right, and query anything that looks odd.
- Get a faulty smart meter fixed. If your smart meter has stopped sending readings, your usage will be estimated instead of measured.
- Know when you use electricity. Before your next renewal, it is worth understanding when in the day your business uses the most. Your meter data can show this.
Jargon buster
| Term | What it means |
|---|---|
| MHHS | Market-wide Half-Hourly Settlement: the change described in this article |
| Settlement | The behind-the-scenes process that works out what each supplier owes for the electricity its customers used |
| Half-hourly meter | A meter that records how much electricity is used in every half hour. Most larger business sites have one |
| Smart meter | A meter that sends readings to your supplier automatically and can record half-hourly usage |
| MPAN | Meter Point Administration Number: the long number on your electricity bill that identifies your supply |
| Ofgem | The energy regulator for Great Britain |
| Elexon | The organisation that runs the settlement system for the electricity industry |
Need a hand?
If your supplier has written to you about MHHS and something does not make sense, or you would like to see when your business uses its electricity and what that could mean at your next renewal, book an informal call. There is no charge and no obligation.
Sources
- Ofgem: Electricity retail market-wide half-hourly settlement, decision and full business case (20 April 2021)
- MHHS Programme: key programme milestones
- Elexon: Market-wide Half Hourly Settlement and the BSC
- Elexon: Profiling
- Elexon: New settlement timetable reducing from 14 months to seven months from April 2027 (May 2026)
- Association of Meter Operators: MHHS Programme reaches 20.2 million meter migrations (September 2026)
- npower Business Solutions: MHHS reform
This article reflects our understanding at the date of publication. Updated 7 October 2026 to add the move to a seven-month timetable from April 2027. It is general information, not advice on any individual contract.