Last updated: 16 October 2026
TNUoS charges pay for the high voltage transmission network, and they are one of several non-commodity costs that sit on every business electricity bill alongside the cost of the energy itself. Together these charges now make up the majority of what many firms pay for electricity. This guide explains what TNUoS is, how it is charged to businesses, what the other non-commodity costs cover and how to check whether your contract fixes them or passes them through.
What is TNUoS?
TNUoS stands for Transmission Network Use of System. It is the charge that recovers the cost of installing and maintaining the transmission system in England, Wales, Scotland and offshore, according to the National Energy System Operator (NESO).
NESO sets the tariffs each year. It publishes the annual tariffs by 31 January, taking effect from 1 April, with forecasts and drafts released during the year.
Generators and suppliers both pay TNUoS. Your supplier pays it on the electricity your site takes from the grid, then recovers it from you through your bill, as SmartestEnergy explains in its guide to non-commodity charges.
How are TNUoS charges applied to business electricity bills?
Most TNUoS is now charged as a fixed daily amount per site, not per unit used. SmartestEnergy says fixed residual charges make up over 90% of TNUoS costs, so most of it is recovered through standing charges whatever you consume.
This follows Ofgem’s Targeted Charging Review, which decided that residual charges will be levied as fixed charges for all households and businesses. Ofgem’s decision on billing the transmission demand residual by site took effect from 1 April 2023.
Residual bands and fixed site charges
NESO’s TNUoS in 10 Minutes guide sets out how the fixed part works:
- The transmission demand residual is charged as a £ per site per day tariff.
- Non-domestic sites are placed in bands based on capacity or consumption, and stay in that band for the length of the price control.
- The same bands apply to TNUoS and DUoS charges.
- Each band’s share is spread across its sites, so every site in a band pays the same daily amount.
Demand charges for half hourly and non half hourly sites
There is still a smaller usage based element, and it depends on your meter. NESO explains that for half hourly (HH) sites, the charge is based on metered demand during the three Triad periods, the three half hours of highest net system demand between November and February.
For non half hourly (NHH) sites, the charge is based on consumption between 4pm and 7pm. Both elements vary by location, with tariffs set for 14 demand zones.
Why are TNUoS charges going up?
TNUoS has risen sharply because the grid is being expanded and reinforced to connect more renewable generation. SmartestEnergy reported that NESO’s 2026/27 tariffs brought average business TNUoS increases of around 60% to 64% from April 2026, one of the largest year on year rises recorded.
The same SmartestEnergy analysis gives the wider picture:
- Total TNUoS revenues are projected to rise from £8.9bn in 2026/27 to £13.6bn by 2030/31.
- Electricity bills are expected to rise 5% to 10% for many businesses because of TNUoS alone.
- TNUoS could grow from about 8% of corporate bills today to 15%, and potentially 23% by 2030/31.
SmartestEnergy also notes that TNUoS is due to be re-banded under the next five year price control, so the band your site sits in may change.
What are non-commodity costs?
Non-commodity costs are every part of your electricity price that is not the wholesale energy itself. SEFE Energy describes a bill as the wholesale cost plus transportation charges, regulatory levies and other third party costs.
They are now the larger share. SmartestEnergy says non-commodity charges make up more than half of a typical business energy bill and describes them as the majority of the retail electricity cost stack.
Wholesale prices still matter. NGP notes that government estimates suggest gas sets the British power price around 60% of the time, and it reported Winter 26 power at 14.78p/kWh in the week to 25 September 2026. That figure is energy only, before any of the charges below are added. For more on the wholesale side, read what affects business electricity prices.
Non-commodity costs at a glance
| Charge | What it pays for | Source |
|---|---|---|
| TNUoS | Installing and maintaining the high voltage transmission network | NESO |
| DUoS (Distribution Use of System) | Installing, running and maintaining the regional distribution network | SmartestEnergy |
| BSUoS (Balancing Services Use of System) | The day to day cost of operating and balancing the transmission system | NESO |
| Renewables Obligation (RO) | Support for renewable generators through certificates suppliers must buy; around £33 to £35 per MWh | SmartestEnergy |
| Feed in Tariff (FiT) | Support for small scale renewable generation at a government set price per unit | SmartestEnergy |
| Contracts for Difference (CfD) | A guaranteed price for low carbon generators, held with the Low Carbon Contracts Company | SmartestEnergy |
| Capacity Market (CM) | Payments to generators and demand side response providers to be available in winter | SmartestEnergy |
| Nuclear RAB | A levy on electricity suppliers to fund Sizewell C | LCCC, SEFE |
| Climate Change Levy (CCL) | Environmental tax on business energy; £0.00801 per kWh for electricity from 1 April 2026 | gov.uk |
| VAT | Standard rate of 20% for most business use, with a reduced rate for qualifying use | gov.uk, HMRC |
What are DUoS charges?
DUoS charges pay for the local network that carries power from the transmission grid to your premises. SmartestEnergy notes there are 14 distribution networks across the UK, excluding Northern Ireland, plus a small but growing number of independent networks.
Your DUoS cost depends on which network area you are in and your meter type. NESO confirms the same residual bands apply to DUoS and TNUoS, with distribution bands based on maximum import capacity or, where there is none, consumption. SmartestEnergy says DUoS is moving towards more fixed and capacity based tariffs.
What is BSUoS?
BSUoS covers the cost of keeping supply and demand matched second by second and the network secure. Since 1 April 2023, NESO says BSUoS has been recovered solely from final demand, and is set as a fixed tariff in advance rather than varying day to day.
SmartestEnergy expects BSUoS costs to remain elevated.
What are the policy levies on a business electricity bill?
Policy levies fund low carbon generation and security of supply. They are charged to suppliers and passed on to you through your unit rate.
- Renewables Obligation: SmartestEnergy calls it the largest subsidy, adding around £33 to £35 per MWh to electricity prices.
- Feed in Tariff: smaller than the RO but still material.
- Contracts for Difference: costs are growing in scale and volatility as more projects come online.
- Capacity Market: recent T-4 auctions cleared at around £65/kW/year, up from the mid £40s a few years ago, and consumers pay through charges on winter consumption.
What is the Nuclear RAB levy for business?
The Nuclear RAB levy funds Sizewell C under the regulated asset base model. The Low Carbon Contracts Company (LCCC) collects it from electricity suppliers, with collections linked to the Revenue Collection Contract it signed with Sizewell C Limited on 4 November 2025.
LCCC publishes the current interim levy rate on its Nuclear RAB dashboard rather than as a fixed figure. Because it is new, SEFE lists it among the charges to check in any fixed price quote.
Are CCL and VAT non-commodity costs?
Yes, they are taxes rather than network or policy charges, and both are set by government. The main CCL rate for electricity is £0.00801 per kWh from 1 April 2026, rising to £0.00827 from 1 April 2027.
VAT is charged at the standard rate of 20% on most business use. Low users under the de minimis limit, or sites where 60% or more is qualifying use, can get the reduced rate under HMRC Notice 701/19. Our guide to VAT on business electricity covers the detail.
Is your fixed price contract truly fixed?
Not always. SEFE warns that not all “fixed” contracts are the same, and some pass-through contracts are marketed as fully fixed.
This matters more now because TNUoS rose so steeply in April 2026 and Nuclear RAB is a new charge. If those costs are passed through, your bill can rise during the contract even though your energy price is fixed.
SEFE’s checklist is a simple test for any quote:
- Are all non-commodity charges included in the price?
- Are newer charges such as Nuclear RAB and revised TNUoS built in?
- Is there a pass-through clause anywhere in the terms?
- Are both the unit rate and the standing charge fixed?
- Is the contract described clearly as fully fixed or pass-through?
Even on a fully fixed deal, SEFE notes that government levies and taxes can still change.
Fully fixed vs pass-through contracts
| Feature | Fully fixed | Pass-through |
|---|---|---|
| Wholesale energy | Fixed for the term | Usually fixed for the term |
| TNUoS, DUoS, BSUoS | Built into the price | Charged at the actual rate, so can rise |
| Policy levies (RO, FiT, CfD, CM, Nuclear RAB) | Built into the price | Charged at the actual rate, so can rise |
| CCL and VAT | Can still change if government changes them | Can still change if government changes them |
| Bill certainty | Higher | Lower |
| Who carries the risk | The supplier | You |
SmartestEnergy, for example, lets customers fix the wholesale portion and choose whether to fix non-commodity costs or pass them through. Neither is right for everyone, so the choice depends on how much bill certainty your business needs.
How do you check what your contract includes?
Start with your contract terms and your latest bill. Look for the words “pass-through”, “third party costs” or “non-commodity” in the terms, and check whether network charges or levies appear as separate lines on the bill.
Then work through these steps:
- Find your band: your standing charge reflects your residual band, so a large jump at renewal may be TNUoS and DUoS rather than supplier margin.
- Check your meter type: HH sites can face Triad based TNUoS charges, so ask how these are treated.
- Ask about Nuclear RAB: confirm in writing whether it is included.
- Compare like with like: set each quote against the same consumption and the same fixed or pass-through basis.
A business energy comparison only works if every quote is built the same way. If you are close to renewal, our business energy contract renewal guide explains the timings.
If you are unsure what you are paying for, a free UMW Health Check reviews your bills and supplier paperwork and checks the charges against your contract.
Frequently asked questions
What is TNUoS on my electricity bill?
TNUoS is the Transmission Network Use of System charge, which pays for the high voltage grid. NESO sets the tariffs each year, and your supplier passes the cost to you, mostly through the standing charge.
Who sets TNUoS charges?
The National Energy System Operator calculates and publishes them. Final tariffs are published by 31 January and apply from 1 April.
Why has my standing charge gone up?
Most TNUoS is now recovered as a fixed daily charge per site, and SmartestEnergy reported average business TNUoS increases of around 60% to 64% from April 2026. If your contract passes these costs through, or you renewed after April, your standing charge will reflect the higher rate.
Can I reduce my TNUoS charges?
The fixed residual element depends on your band, so using less will not change it much. SmartestEnergy suggests load shifting, demand flexibility and on site generation such as solar and storage to reduce exposure to grid costs.
What is the difference between TNUoS and DUoS?
TNUoS pays for the national high voltage transmission network. DUoS pays for the regional distribution network that carries power to your site, and it varies by network area.
What share of my bill is non-commodity costs?
SmartestEnergy says non-commodity charges make up more than half of a typical business energy bill. The exact share varies with your usage, location, meter and contract.
Is Nuclear RAB included in fixed contracts?
It depends on the contract. SEFE advises checking whether new charges like Nuclear RAB are built into the price or passed through.
Do non-commodity costs apply to business gas too?
Gas bills also carry transportation and other third party costs, but TNUoS, DUoS, BSUoS and the electricity levies covered here apply to electricity. See our business gas page for gas contracts.
Get a quote
Utility Market Watch compares business electricity from a panel of suppliers and can explain which charges each quote fixes and which it passes through. Request a quote, call 03333 601010 (Monday to Friday, 9am to 5pm) or contact us. Our service is paid for by the supplier through a commission included in your unit rate, and as prices change daily we cannot guarantee any quote is the cheapest.