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TNUOS & DUOS: A short guide to non-commodity charges.

Non-commodity costs often make up more of your electricity invoice than the actual electricity does.

This means that knowing who is responsible for the transmission and distribution charges is important plus it may impact all sorts of business decisions – such as when to run the highest consuming pieces of equipment or even what areas the HQ and offices should be located to optimise costs.

Here you can get a better understanding of the TNUOS and DUOS non-commodity charges in your electricity bill with our short guide.

Firstly, we’ll put TNUoS & DUoS in context. Secondly, we’ll tackle the acronyms and lastly how you can try to reduce these charges.

How suppliers buy electricity

Suppliers buy electricity from generation companies.

They are charged by the National Transmission Network and Distribution Network Operators (DNOs) and Independent DNOs who deliver electricity to your buildings.

The Supplier passes these charges to you – shown as Network and Distribution charges in your electricity bill.

These charges help maintain the various local and national electricity networks we all use.

Transmission Networks

Electricity Transmission networks are over and underground. They’re most recognisable as electricity pylons.

These networks are managed by the National Grid who install and maintain the system across England, Wales, Scotland and offshore. The map of networks is available on their website.

After that, it enters the Distribution Network and is delivered to homes and businesses.

The Distribution Network is run by Distribution Network Operators (DNOs) and Independent Distribution Network Operators (IDNOs), like Stark Infra.

What does TNUoS stand for?

TNUoS is the Transmission Network Use of Service. It’s sometimes referred to as TUoS – Transmission Use of System.

These charges help maintain the various local and national electricity networks we all use.

How are TNUoS charges calculated?

Your charge is based on your share of demand on the transmission network during its peak periods (Triads).

Triad periods occur between 1st November and 28th February each year when demand on the National Grid is at its highest.

What does DUoS mean?

DUoS stands for Distribution Use of Service.

Distribution Network Operators (DNOs), or Independent Distribution Network Operators, (iDNOs) like Stark Infra, install and maintain local networks.

How are charges calculated?

The charge you receive will be based on the amount of electricity you’re using which has passed through the iDNO, or DNOs network.

Each Network Operator has different rates and the time the electricity is being used will affect the cost as well. If you’re using electricity at peak demand times it will cost more.

You can identify which rates apply by finding the ‘Line Loss Factor’ for your site and looking it up on your DNO’s scale of charges.

  • The Line Loss Factor is the last 3 digits of your electricity supply’s Meter Point Administration Number (MPAN).
  • An MPAN is a 13-digit unique number for each electricity supply which you can find on the invoice relating to the supply.

How do I reduce non-commodity TNUOS & DUOS charges?

One surefire way to keep on top of these charges is by monitoring your HH electricity data.

  1. Reduce the overall amount of electricity you’re asking the Transmission and Network Operators to transport for you,
  2. Reduce the amount of electricity consumed at peak demand times of the day

If you can achieve this then you’ll have more chance to reduce your non-commodity costs.

One easy way to track your TNUOS and DUOS charges

If you’re a Stark customer you can access our Cost Reports in Stark ID, our online energy analytics platform.

Our Stark ID Cost Reports will show you what the TNUOS and DUOS charges are compared to your actual electricity consumption.

You will also be able to monitor the most expensive times of day to use electricity so you can identify any opportunities to shift operations to save costs.


In summary, TNOUS and DUOS charges are billed by the Supplier and cover the maintenance and other costs associated with running a national and local electricity network.

TNOUS is for the transmission network run by National Grid, and DUOS are the Distribution charges from your local Distribuion Network Operator (DNO), or Independent DNO (IDNO).

The charges you receive depend on who your DNO or IDNO is, how much electricity you use, and importantly when you use it.

You can help manage these costs by making strategic business decisions on how and when to run high-consuming equipment, as well as monitoring your non-commodity costs in Stark ID Cost Reporting.

Got questions? Contact our team

Our team of experts are here to help. So if you want to see how Stark can help you with your electricity data or simply set up Stark ID Cost Reporting please get in touch.

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Home » TNUOS & DUOS | A short guide to non-commodity charges