TNUoS charges explained: what businesses pay in 2026/27

What are TNUoS charges?

TNUoS stands for Transmission Network Use of System. These charges recover the cost of installing and maintaining the electricity transmission system in England, Wales, Scotland and offshore: the high-voltage part of the network.

They're one of several network charges built into business electricity prices. The local network that brings electricity to your premises is paid for separately, through distribution charges, which you may see called DUoS.

TNUoS applies in Great Britain only. Northern Ireland has its own network charges.

Who sets TNUoS charges, and who pays them?

The National Energy System Operator, NESO, works out and publishes the tariffs. It's a publicly owned body that started on 1 October 2024, after the government bought the electricity system operator from National Grid.

NESO publishes the tariffs each year by 31 January, and they take effect from 1 April. Before that, it publishes forecasts through the year and draft tariffs, usually by the end of November.

Two groups pay:

• generators, based on the capacity they're allowed to put onto the transmission system;
• electricity suppliers, based on their customers' demand.

For 2026/27, NESO expects to collect £7.61 billion in total: £1.23 billion from generators and £6.38 billion from demand, mostly through suppliers. Suppliers then recover what they pay through their customers' prices.

How are TNUoS charges calculated for a business?

The demand side of TNUoS has two parts.

1. The residual charge, a fixed amount per site per day, set by your site's band. Every site in the same band pays the same, wherever it is. NESO says about 98% of demand revenue is collected this way.
2. The locational charge, which depends on where your site is and when you use electricity. Sites in zones 1 to 7 (Scotland, northern England, North Wales and Merseyside, and the East Midlands) pay nothing for this part in 2026/27, because demand tariffs there are held at zero.

How the locational charge works depends on your meter:

• Half-hourly sites pay in pounds per kW, based on what they use during the Triads (see below). The average half-hourly tariff for 2026/27 is £2.79 per kW.
• Other sites pay in pence per kWh on the electricity they use between 4pm and 7pm, every day of the year. The average for 2026/27 is 0.38p per kWh.

TNUoS charges for 2026/27: the fixed charge by band

These are NESO's final residual charges for 2026/27, per site per day. Smaller sites without an agreed capacity are banded by how much electricity they use in a year. Larger sites are banded by their agreed capacity in kVA and the voltage they're connected at, and sites connected directly to the transmission network by how much they use.

For comparison, every home pays 22p a day.

The band thresholds were reset in April 2026 for the new price control period, and NESO says they'll stay the same until it ends in 2031. If you don't know your site's band, ask your supplier.

Working out a site's TNUoS cost: an example

Take a smaller site in band 3, which uses between 13,677 and 27,543 kWh a year. Its residual charge for 2026/27 is £1.24 a day, which comes to about £453 over the year.

If that site isn't half-hourly and uses 4,000 kWh between 4pm and 7pm over the year, the average locational tariff of 0.38p per kWh would add about £15. The real figure depends on the site's zone, and sites in zones 1 to 7 pay nothing for this part.

A half-hourly site that uses an average of 100 kW across the three Triads would pay about £279 for the locational part, at the average half-hourly tariff of £2.79 per kW. Again, the real figure depends on its zone.

These are the charges your supplier pays for your site. What you pay depends on how your supplier builds them into your prices.

What are Triads?

Triads are the three half hours of highest net demand on the national system between November and February, each separated by at least ten full days. A half-hourly site's locational TNUoS charge is based on how much electricity it uses in those three half hours.

The Triads are only identified once the winter is over, so you can't know in advance exactly when they'll fall. Triad charging is still in place for 2026/27. A proposed change to the industry rules, known as CMP440, would remove the zero floor, so sites in some northern zones could get negative charges. The original proposal bases these on use between 4pm and 7pm, while an alternative would spread them across all use. The proposed start is 1 April 2027, and Ofgem hadn't decided when we last checked in October 2026.

Why are TNUoS charges increasing?

The total to be collected through TNUoS rose from £5.09 billion in 2025/26 to £7.61 billion in 2026/27, an increase of £2.52 billion. NESO says the residual tariffs went up by 63% on average. Because the band thresholds also changed in April 2026, the change for an individual site depends on its band.

The rise came with a new price control for the transmission companies, called RIIO-3, which runs from 1 April 2026 to 31 March 2031. Ofgem's final decision set £10.7 billion of upfront funding for electricity transmission and said over £70 billion of investment may be needed across the period, to upgrade the grid to meet new demands.

Not everything went up. The average half-hourly locational tariff fell from £8.49 per kW in 2025/26 to £2.79 per kW in 2026/27.

TNUoS charges for 2027/28: NESO's forecast

NESO's latest forecast, published on 14 October 2026, expects total TNUoS revenue of £9.5 billion in 2027/28, with £7.97 billion coming from the demand residual. Its forecast residual charges for smaller and low-voltage sites are:

NESO forecasts the average half-hourly tariff at £3.29 per kW and the average for other sites at 0.46p per kWh. These are forecasts, not final tariffs. NESO is due to publish draft 2027/28 tariffs by 30 November 2026 and final tariffs by 31 January 2027.

How TNUoS shows on a business electricity bill

You may not see TNUoS as a separate line on your bill. Your supplier pays it and builds it into your prices, and Ofgem notes that the fixed network charges may be passed on as standing charges, but that this isn't guaranteed. How they reach you depends on your contract.

• On a fixed-rate contract, Ofgem says your unit rates and standing charges are fixed for the length of the contract.
• On a pass-through contract, some network costs are passed on at cost, so they can change during the contract, for example each April.

If your bill lists network charges separately, our guide to reading a business electricity bill explains the other lines you may see.

TNUoS, DUoS and BSUoS: what's the difference?

Three industry charges are often mentioned together:

• TNUoS pays for the high-voltage transmission network, and is set by NESO.
• DUoS, distribution use of system charges, pays for your local network, and is set by your regional network operator.
• BSUoS, balancing services use of system charges, covers the cost of running the system day to day. Since 1 April 2023, it has been charged only to final demand, at a fixed tariff set in advance.

All three are usually charged to your supplier, which recovers them through your prices.