What is TNUoS and why does it affect businesses?

TNUoS stands for Transmission Network Use of System. It is a charge on electricity bills that helps pay for the high-voltage transmission network that moves electricity around Great Britain.

For businesses, TNUoS matters because it is one of the non-commodity charges that can increase electricity bills even when wholesale electricity prices are stable or falling. It is especially important in 2026 because TNUoS charges have risen sharply from April 2026, adding pressure to many business electricity contracts. NESO publishes the official TNUoS charging information and final tariffs, including the final 2026/27 tariffs published on 30 January 2026.

Summary answer

Question	Answer
What does TNUoS mean?	Transmission Network Use of System
What does it pay for?	The high-voltage electricity transmission network
Who sets the charges?	NESO calculates and publishes TNUoS tariffs
Who ultimately pays?	Electricity suppliers recover the cost from customers, including businesses
Is TNUoS a wholesale electricity cost?	No, it is a non-commodity network charge
Does it affect gas bills?	No, TNUoS is an electricity charge
Why is it important in 2026?	Charges have increased sharply from April 2026
Does every business pay the same?	No, impact varies by site, meter type, region, voltage level and contract
Can businesses avoid it completely?	Usually no, but they may reduce exposure through efficiency, capacity reviews and contract structure

What does TNUoS pay for?

TNUoS pays for the cost of the electricity transmission network. This is the high-voltage system that moves power from large generators, interconnectors and transmission-connected assets to the regional distribution networks.

It helps fund:

• high-voltage overhead lines
• underground and subsea cables
• major substations
• transmission network maintenance
• transmission upgrades
• grid reinforcement
• offshore transmission infrastructure
• the cost of connecting and moving electricity from new generation sources

A useful way to think about it is that TNUoS pays for the electricity “motorway network”, while DUoS pays for the local electricity “road network”.

Charge	What it covers	Simple comparison
TNUoS	National high-voltage transmission system	Electricity motorways
DUoS	Regional and local distribution networks	Local roads
BSUoS	Balancing the electricity system in real time	Traffic control

Why do businesses pay TNUoS?

Businesses pay TNUoS because they use the electricity system. Even if a business buys electricity from a supplier, the electricity still has to travel through national and local infrastructure before it reaches the premises.

The supplier usually pays industry charges and then recovers them from customers through the unit rate, standing charge, pass-through costs or separate invoice lines.

For smaller businesses, TNUoS is usually hidden inside the electricity price. For larger businesses, especially those with half-hourly meters or pass-through contracts, TNUoS may be more visible.

Business type	How TNUoS may appear
Small office or shop	Usually bundled into the unit rate or standing charge
Café, salon or small retail site	Usually included in supplier pricing
Half-hourly metered site	May be more directly reflected in standing charges or pass-through costs
Large manufacturer	Often more visible and financially significant
Multi-site business	May vary by location and meter type
Flexible procurement customer	Often treated as a separate forecast or pass-through item

Why TNUoS affects business electricity bills in 2026

TNUoS is a major 2026 issue because charges have increased sharply. EDF says the average £/MWh equivalent residual charge for 2026/27 is around £25.70/MWh, up from around £15.70/MWh, which represents an increase of roughly £10/MWh year on year.

That £10/MWh increase is equivalent to about 1p/kWh. For a small user, that may be noticeable. For a larger user, it can be a major annual cost increase.

Annual electricity use	Approximate extra cost from £10/MWh increase
10,000kWh	£100 per year
25,000kWh	£250 per year
50,000kWh	£500 per year
100,000kWh	£1,000 per year
250,000kWh	£2,500 per year
500,000kWh	£5,000 per year
1,000,000kWh	£10,000 per year
5,000,000kWh	£50,000 per year

These are simplified figures. Actual TNUoS impact depends on the site’s location, meter type, voltage level, charging band, supplier contract and whether the charge is fixed or passed through.

Why has TNUoS increased?

TNUoS is rising because the electricity transmission system needs major investment. The UK is changing where and how electricity is generated, with more offshore wind, renewable generation, interconnectors, storage, electrification and large demand projects such as data centres.

That means the grid needs more capacity, more reinforcement and more connections. NESO’s 2026/27 material notes pointed to a forecast total TNUoS revenue of £6.2 billion, an increase of £1.2 billion from the 2025/26 final tariffs, with increases linked to onshore and offshore transmission owner revenue and other pass-through items.

For businesses, the practical point is that the cost of upgrading and operating the transmission system is increasingly being felt through electricity bills.

Is TNUoS the same as wholesale electricity?

No. TNUoS is not the wholesale cost of electricity.

Wholesale electricity is the cost of buying the power itself. TNUoS is the cost of using the high-voltage transmission network.

Cost	What it means
Wholesale electricity	The cost of buying electricity from the market
TNUoS	The cost of using the transmission network
DUoS	The cost of using local distribution networks
BSUoS	The cost of balancing the electricity system
Supplier margin	Supplier operating costs and profit
Policy costs	Charges such as RO, FiT, CfD and Capacity Market
Taxes	VAT and Climate Change Levy

This is why a business electricity bill can rise even if wholesale electricity prices fall. The wholesale element may be lower, while network and policy charges are higher.

How is TNUoS different from DUoS?

TNUoS and DUoS are both network charges, but they pay for different parts of the electricity system.

Feature	TNUoS	DUoS
Full name	Transmission Network Use of System	Distribution Use of System
Network level	National high-voltage network	Regional and local networks
Main purpose	Moving electricity across Great Britain	Delivering electricity locally to premises
Applies to	Electricity bills	Electricity bills
Varies by	Location, voltage, meter type, charging band and methodology	Region, voltage, meter type, time band and capacity
Commonly visible to SMEs?	Usually bundled	Usually bundled
More visible to large users?	Yes	Yes

A simple example: electricity generated by an offshore wind farm may travel across the high-voltage transmission system, then through regional distribution networks before reaching a business. TNUoS relates to the first part of that journey; DUoS relates to the local delivery.

How is TNUoS different from BSUoS?

BSUoS stands for Balancing Services Use of System. It pays for the cost of keeping the electricity system balanced in real time. NESO says BSUoS recovers the cost of day-to-day system operation, including balancing the electricity transmission system.

Charge	What it pays for
TNUoS	Building, operating and upgrading the transmission network
DUoS	Local distribution network costs
BSUoS	Balancing supply and demand on the electricity system

TNUoS is about transmission infrastructure. BSUoS is about real-time system operation.

Why does TNUoS appear in standing charges?

TNUoS can be recovered through standing charges, particularly where residual charges are involved. EDF notes that TNUoS residual charges are recovered through standing charges expressed in £/site/day, even though the average £/MWh equivalent is often used for comparison.

This is one reason businesses may see standing charges rise even if their electricity consumption has not increased.

Example	What happens
Unit rate unchanged, standing charge rises	Total bill increases despite stable usage
Usage falls, standing charge rises	Savings are smaller than expected
Business uses very little electricity	Standing charge becomes a larger share of total bill
Larger site has higher residual band	Fixed daily cost may rise significantly

For low-usage businesses, higher standing charges can be especially frustrating because the cost is fixed regardless of how much electricity is used.

Why does TNUoS vary between businesses?

TNUoS is not the same for every business. The impact can vary because of:

• location
• region
• meter type
• half-hourly or non-half-hourly status
• voltage level
• line loss factor class
• agreed capacity
• charging band
• annual consumption
• contract type
• supplier pricing method

This means two businesses using the same amount of electricity may not face exactly the same TNUoS cost.

Factor	Why it matters
Location	Transmission costs vary across the system
Meter type	Half-hourly and non-half-hourly sites may be treated differently
Voltage level	Larger or higher-voltage sites can fall into different charging groups
Charging band	Residual charges can depend on banding
Contract structure	Fixed contracts and pass-through contracts treat TNUoS differently
Supplier approach	Some suppliers bundle TNUoS; others itemise or reconcile it

Does TNUoS affect small businesses?

Yes, but often indirectly. A small business may not see a line on its bill labelled “TNUoS”, but the cost can still be included in the standing charge or unit rate.

For example, a small shop or office may simply see:

• a higher standing charge
• a higher renewal quote
• a higher pence-per-kWh unit rate
• a supplier explanation that “network costs” have increased

That increase may partly reflect TNUoS, even if the bill does not mention it by name.

Does TNUoS affect large businesses more?

Usually, yes. Larger electricity users are more exposed because even small changes in £/MWh can create large annual cost increases.

Business type	Why TNUoS can matter
Manufacturer	High electricity usage magnifies £/MWh increases
Cold storage site	Continuous demand means network charges are material
Warehouse	Lighting, automation, HVAC and EV charging increase exposure
Hotel	High electricity use across kitchens, laundry, lifts, lighting and HVAC
Care home	Continuous operation creates high annual consumption
Leisure centre	Pools, gyms, lighting and heating systems increase electricity demand
Multi-site retailer	Small increases multiplied across many sites become significant
Data centre	High power demand makes transmission charges strategically important

A large business using 1,000,000kWh per year could face an extra £10,000 per year from a £10/MWh increase alone. A business using 5,000,000kWh could face an extra £50,000 per year.

Does TNUoS affect fixed energy contracts?

It depends on the contract.

Some contracts are fully fixed, meaning the supplier has built forecast TNUoS costs into the price. Others are pass-through or partly pass-through, meaning TNUoS can be adjusted during the contract.

Contract type	TNUoS treatment
Fully fixed contract	TNUoS usually included in fixed rate, subject to contract wording
Fixed contract with exclusions	TNUoS may be passed through or reconciled later
Pass-through contract	TNUoS billed at actual or updated cost
Flexible contract	TNUoS usually forecast, passed through or separately managed

This is why businesses should check the wording carefully. A contract described as “fixed” may not fix every non-commodity charge.

Why TNUoS matters for pass-through contracts

TNUoS is one of the biggest risks in a pass-through electricity contract. If the supplier passes through actual TNUoS costs, the business can face increases even after signing.

For example:

Annual usage	Extra cost if TNUoS rises by £5/MWh	Extra cost if TNUoS rises by £10/MWh	Extra cost if TNUoS rises by £15/MWh
50,000kWh	£250	£500	£750
100,000kWh	£500	£1,000	£1,500
250,000kWh	£1,250	£2,500	£3,750
500,000kWh	£2,500	£5,000	£7,500
1,000,000kWh	£5,000	£10,000	£15,000
5,000,000kWh	£25,000	£50,000	£75,000

This is why a low headline unit rate can be misleading if TNUoS and other non-commodity charges are not fixed.

Can businesses reduce TNUoS costs?

Most businesses cannot avoid TNUoS completely. It is part of the cost of using the electricity system. However, some businesses can reduce their exposure.

Action	How it may help
Reduce imported electricity	Lower grid consumption can reduce some usage-linked exposure
Install solar panels	Reduces electricity imported from the grid during daylight hours
Add battery storage	Can reduce peak import and increase solar self-consumption
Review agreed supply capacity	May reduce fixed capacity-related network costs where applicable
Improve energy efficiency	Reduces total kWh use
Check contract structure	Avoids unexpected pass-through increases
Monitor half-hourly data	Helps identify peak demand and unusual consumption
Compare suppliers early	Allows better assessment of fixed versus pass-through offers
Check meter and site details	Incorrect meter data or banding can affect charges

The right strategy depends on the size and type of business. A small office may focus on contract choice and standing charges. A manufacturer may need a more detailed review of capacity, half-hourly data, solar, batteries and demand management.

Should businesses choose fixed or pass-through TNUoS?

There is no single answer. It depends on whether the business values budget certainty or cost transparency.

Option	Advantage	Disadvantage
Fixed TNUoS	Better budget certainty	Supplier may include a risk premium
Pass-through TNUoS	More transparent and may be cheaper if charges fall	Business takes the risk if charges rise
Reconciled TNUoS	Can reflect actual costs more closely	May create catch-up charges
Flexible procurement	Suitable for larger energy users	Requires expertise and active management

For many SMEs, a fully fixed contract is easier to budget. For large half-hourly users, a pass-through or flexible approach may make sense, but only if the business understands the risk.

What should businesses ask suppliers about TNUoS?

Before signing a business electricity contract, ask:

Question	Why it matters
Is TNUoS fixed for the full contract?	Confirms budget certainty
Is TNUoS included in the unit rate or standing charge?	Shows where the cost is hidden
Can TNUoS be passed through later?	Identifies future price risk
Will TNUoS be reconciled?	Warns of possible catch-up invoices
What assumptions have been used?	Helps compare quotes fairly
How does my meter type affect TNUoS?	Important for half-hourly sites
How does my region affect TNUoS?	Charges can vary by location
Is broker commission added on top?	Prevents misleading quote comparisons
What is the estimated annual TNUoS cost?	Gives a clearer view of total cost
Can I see a fully fixed alternative?	Helps compare risk against price

A supplier or broker should be able to explain whether TNUoS is fixed, passed through or excluded from the quote. If they cannot, the contract may be difficult to manage.

How to check whether TNUoS has affected your bill

A business should check:

Item to check	What it tells you
Standing charge	TNUoS residual increases may appear here
Unit rate	Supplier may have bundled TNUoS into p/kWh
Contract renewal date	New TNUoS assumptions may apply after renewal
Pass-through clauses	Confirms whether TNUoS can change during the contract
Supplier invoice notes	Some suppliers show non-commodity adjustments separately
Half-hourly statement	Larger sites may see more detail
MPAN and meter type	Confirms whether the correct charging basis is being used
Site capacity	Larger capacity may increase fixed network exposure
Broker quote sheet	May show whether TNUoS was included or excluded

If a bill has risen sharply from April 2026, TNUoS should be one of the first items to check alongside DUoS, BSUoS, standing charges and contract renewal rates.

Worked example: small business impact

A small business uses 30,000kWh of electricity per year.

Item	Before increase	After increase
Annual use	30,000kWh	30,000kWh
TNUoS-equivalent cost	£15.70/MWh	£25.70/MWh
Approximate annual TNUoS cost	£471	£771
Approximate increase	—	£300

This does not mean every small business will see exactly a £300 increase. It shows how a £10/MWh increase translates into annual cost for a 30,000kWh user.

Why TNUoS is part of the wider electricity cost problem

TNUoS is one of several non-commodity charges that are becoming more important on business electricity bills. Businesses are often told that wholesale electricity prices have fallen from crisis peaks, but final bills remain high because other costs have risen.

These include:

• TNUoS
• DUoS
• BSUoS
• Renewables Obligation
• Feed-in Tariff
• Contracts for Difference
• Capacity Market
• metering costs
• supplier operating costs
• broker commission
• VAT and Climate Change Levy

For many businesses, the final electricity price is now as much about infrastructure and policy costs as it is about wholesale electricity.

Does TNUoS encourage better use of the grid?

In principle, network charges are intended to recover the cost of electricity infrastructure and send signals about the cost of using the system. In practice, many businesses experience TNUoS simply as a bill increase.

The policy challenge is that the electricity system needs investment, but businesses also need affordable and predictable power. This is especially important for energy-intensive sectors, manufacturing, cold storage, logistics, hospitality and other businesses where electricity is a major operating cost.

Final verdict

TNUoS is the Transmission Network Use of System charge. It helps pay for the high-voltage electricity network that moves power around Great Britain.

It affects businesses because suppliers recover TNUoS costs through electricity bills. For smaller businesses, it may be hidden inside the standing charge or unit rate. For larger businesses, it may be shown more clearly or passed through as a separate cost.

TNUoS is especially important in 2026 because charges have risen sharply from April 2026. EDF says the average £/MWh equivalent residual charge has increased from around £15.70/MWh to around £25.70/MWh, adding roughly £10/MWh year on year.

For a business using 100,000kWh per year, a £10/MWh increase is roughly £1,000 per year. For a business using 1,000,000kWh, it is roughly £10,000 per year.

The key lesson for businesses is to look beyond the headline unit rate. TNUoS, standing charges, pass-through clauses and other non-commodity costs can have a major effect on the final bill.

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