What Is MHHS? Market-Wide Half-Hourly Settlement Explained

Market-Wide Half-Hourly Settlement (MHHS) is the biggest change to how UK business electricity is billed in over a decade. It's an Ofgem-sponsored, Elexon-delivered reform, and it's already underway. If your business runs a smart or advanced meter, migration is either scheduled or coming.

Here's what MHHS is, when it's happening, and what to check now.

Get a new meter

What is MHHS?

MHHS stands for Market-Wide Half-Hourly Settlement. It's an industry-wide programme that moves electricity billing away from estimated usage and onto actual consumption, recorded and settled every 30 minutes.

Instead of one averaged figure spread across weeks or months, your electricity use is captured in half-hourly blocks. That means your bill starts to reflect not just how much electricity you use, but when you use it.

Half-hourly settlement has applied to large, high-demand sites for years. MHHS extends the same approach to any business with a smart or advanced meter, regardless of size or sector.

Why is MHHS happening?

MHHS supports the UK's move to a more flexible, lower-carbon electricity system. More accurate, granular usage data helps the grid match supply and demand, and makes it easier to bring more renewable generation onto the network.

For businesses, the practical upside is billing that reflects real usage rather than estimates, and the option, over time, of tariffs that reward using electricity outside peak periods.

When is MHHS happening?

September 2025: MHHS central systems went live
October 2025: supplier and meter migrations began
October 2026: around 80% of meters expected to have migrated
May 2027: full migration expected to be complete
July 2027: cutover to the new, faster settlement timeframe

There's nothing you need to do to trigger your own migration. Your supplier is responsible for moving your meter and will contact you before your billing changes.

Will MHHS affect my business energy bills?

For most businesses, no immediate change. Your existing contract, agreed rates and supply stay the same until migration reaches your meter, and your existing contract isn't affected by MHHS until it's due for renewal.

Most businesses won't notice a change to how their bill looks. Only customers with advanced (AMR) meters see a shift in billing presentation once migrated. If you're on a smart or traditional meter, billing continues much as it does now.

For those AMR customers who do see a change, the main difference is where your usage figure comes from. Here's how the two compare:

Half-hourly billing vs non-half-hourly billing

How usage is recorded	Actual usage, captured every 30 minutes	Estimated between meter reads
What appears on your bill	Half-hourly consumption data	Readings estimated from your usage history
Accuracy	Reflects exactly what you used, when	May over or underestimate usage between reads
Standing charge	Unchanged	Unchanged

Illustrative example only. Your actual bill layout may vary by supplier.

Beyond the usage figures, migrated AMR customers may also notice:

Consumption patterns that look different to your historic bills, simply because they're now based on what you actually used, not an average
Changes to invoice formats and line items, depending on your supplier

If you have a Current Transformer (CT) metering arrangement that attracts capacity charges, there's a 12-month protection window from your migration date before those charges can apply. This gives you time to agree your Maximum Import Capacity with your Distribution Network Operator (DNO) if needed.

What's changing on my meter reference number?

Since 22 September 2025, the MPAN (Meter Point Administration Number) top line has used new terminology: Standard Settlement Configuration (SSC) has replaced Meter Time Switch Code (MTC), and DUoS Tariff ID has replaced Line Loss Factor Class (LLFC). This is a naming change on paperwork; it doesn't affect your pricing or contract.

What is a half-hourly meter?

A half-hourly meter automatically records and transmits your electricity usage every 30 minutes, rather than relying on periodic manual or estimated readings. Most smart and advanced meters are already capable of this. Read our full guide to half-hourly meters for more on meter types and what to check on your bill.

What should I do about MHHS?

Check your meter type. It's usually shown on your bill. A smart, advanced or AMR meter, or a Profile Class of 05 to 08, means migration is likely already scheduled.

Ask your supplier for your migration date. Suppliers are required to contact you before your billing changes, but it's worth asking directly if you want to plan.

Review your contract against half-hourly pricing. If you're locked into a fixed rate that doesn't sit comfortably with time-of-use billing, it's worth understanding that before your next renewal rather than after.

Keep your renewal dates visible. myHUB tracks your contracts and renewals in one place, so a change like MHHS migration doesn't land as a surprise.

Frequently asked questions

Is MHHS mandatory?

Yes, for meter migration. Every electricity meter in the UK is being moved to half-hourly settlement as part of the programme. It isn't optional for suppliers or meter operators, though you don't need to take any action yourself.
Do I need a new meter for MHHS?

Not necessarily. Smart, advanced, SMETS1/2 and traditional meters are all being migrated. If your meter can't support half-hourly data, your supplier will let you know what's needed.
Will my supplier contact me about MHHS?

Yes. Suppliers are expected to contact customers whose billing is changing before that change takes effect.
Does MHHS affect gas as well as electricity?

No. MHHS applies to electricity meters only.
We're tracking the MHHS rollout closely. If you want to understand what it means for your specific setup, compare business energy deals with our panel of trusted suppliers, or get in touch and we'll talk you through it.
Sources:MHHS Programme,Elexon,Ofgem