MHHS unpacked: 10 key points explained

The systems underpinning Market-wide Half-Hourly Settlement (MHHS) are now live. This milestone marks a huge change for the electricity industry, whereby we take a significant step towards tracking consumption for every consumer in the country on a half-hourly basis. The aim is to support a more efficient, accurate and flexible electricity system ready for Clean Power 2030.

But what does this mean for you? Here’s your ‘need to know’ guide to MHHS in ten key points.

1. How will this impact my business? 
   Most of the changes happening as a result of MHHS are behind the scenes – for example, new system architecture, industry codes, data and metering roles. So there will be little direct impact to you, as an electricity consumer.
   
   
2. Meters move to new segments
   All electricity meters – including traditional meters – will be migrated into new market segments, instead of the commonly understood concept of Half-Hourly (HH) and Non-Half Hourly (NHH): 
   • The new market segment for HH and AMR will be known as Advanced
   • The new market segment for traditional NHH and Smart will be known as Smart
   • For all unmetered (UMS) metering types, this will stay the same 
     
     
3. Changes to metering services
   Metering services are also changing to reflect the new MHHS requirements as seen on the right-hand side.
   
   
4. Will migration start now?
   Most suppliers won’t start migrating customer meters (MPANs) to the new MHHS arrangements until May 2026 – with an end date of May 2027.
   
   
5. Will there be changes to my invoice?
   However, from 22 September 2025, some topline information will change on all electricity invoices. 
   
   For example: A Standard Settlement Configuration code will replace the three-digit Meter Timeswich code: this will be 0000 for Half-Hourly (HH) meters, and whatever the current system-held value is for Non-Half-Hourly (NHH) meters. 
   
   We will be in touch with nBS customers shortly with more information. So if you receive or validate your invoices using EDI or BASDA files, you may need to test the new format invoice files to ensure your system can handle them. If you're an nBS customers, please contact us if you have not received your test file.
   
   
6. What if I already have a HH meter?
   If your business has HH or Automated Meter Reading (AMR) technology meters, not much should change, as your consumption is already settled on a half-hourly basis.
   
   
7. What changes will I see to my NHH meter data?
   If you have any NHH meters in your portfolio, your consumption will be mapped to a far more sophisticated half-hourly model post migration, using a new load-shaping service to support more accurate settlement.
   
   
8. New Four-Month Settlement Plan
   Speaking of settlement, from July 2027, the current plan (and do note, this can change!) is for the ‘settlement’ window – where actual consumption is reconciled against the electricity volumes purchased by suppliers via a new Central Settlement Service – will reduce, from the current 14 months to just four.
   
   
9. Traditional to Smart: unlocks more insight
   While the introduction of MHHS does not require you to change your meter, upgrading from a traditional NHH to an AMR or Smart meter would provide access to actual half-hourly data to support greater insight and energy efficiency.
   
   
10. What if I need to switch supplier during migration?
    If your supplier is one of the few who qualify early (and can therefore start migrating your meter from October 2025) – but you want to switch to another supplier who isn’t yet MHHS qualified, you can do so via a process called ‘Reverse Migration’. 
    
    

Finally, if you’d like to know more about MHHS – or have any questions – you may like to check out the nBS MHHS Hub.