What are TNUoS Charges?
TNUoS charges cover the costs of maintaining, operating, and expanding the national network, which supplies electricity from generation sources (power stations, wind farms, etc.) to local distribution substations via overhead transmission cables on pylons. Both consumers and generators are subject to TNUoS, levied by the National Energy System Operator (NESO).
In the generator’s case, they will either be charged to cover the load they put on the network or paid a credit, to encourage them to supply more power to the network. While the charge/credit can vary widely, generators are often charged in regions with low demand. This increased cost on the generator is passed through to the end buyer, thus resulting in higher prices for end users.
Upward Trend of TNUoS Charges:
Transmission Demand Residual tariffs are updated annually in April. TNUoS charges on end users have significantly risen across the board from last year (2024), as the table below, containing the last three sets of released charges, shows:
| Band Classification | Unit Measurement | Lower Threshold | Upper Threshold | Band | £/Site/Day: 04/2023 - 03/2024 | £/Site/Day: 04/2024 - 03/2025 | £/Site/Day: 04/2025 - 03/2026 | Percentage Increase 2023 to 2026 |
|---|---|---|---|---|---|---|---|---|
| Low Voltage Non-Half Hourly | Annual Consumption kWh | - | 3,571 | 1st Band | 0.06 | 0.07 | 0.15 | 150% |
| 3,572 | 12,553 | 2nd Band | 0.28 | 0.25 | 0.37 | 32.14% | ||
| 12,554 | 25,279 | 3rd Band | 0.66 | 0.58 | 0.76 | 15.2% | ||
| 25,280 | - | 4th Band | 2.05 | 1.74 | 2.07 | 0.98% | ||
| Low Voltage Half Hourly - Current Transformer | Agreed Supply Capacity kVA | - | 80 | 1st Band | 3.32 | 3.13 | 3.91 | 17.77% |
| 81 | 150 | 2nd Band | 6.09 | 5.32 | 6.53 | 7.22% | ||
| 151 | 231 | 3rd Band | 9.91 | 8.49 | 10.25 | 3.43% | ||
| 232 | - | 4th Band | 22.32 | 19.79 | 22.74 | 1.88% | ||
| High Voltage | Agreed Supply Capacity kVA | - | 422 | 1st Band | 17.27 | 16.46 | 21.83 | 26.40% |
| 423 | 1,000 | 2nd Band | 55.58 | 49.66 | 62.80 | 12.99% | ||
| 1,001 | 1,800 | 3rd Band | 109.14 | 95.29 | 121.80 | 11.60% | ||
| 1,801 | - | 4th Band | 276.99 | 243.63 | 317.60 | 14.66% | ||
| Extra High Voltage | Agreed Supply Capacity kVA | - | 5,000 | 1st Band | 130.70 | 132.85 | 160.77 | 23.01% |
| 5,001 | 12,000 | 2nd Band | 642.65 | 668.54 | 741.79 | 15.43% | ||
| 12,001 | 21,500 | 3rd Band | 1,295.79 | 1,255.85 | 1,576.23 | 21.64% | ||
| 21,501 | - | 4th Band | 3,528.82 | 3,520.06 | 3,882.74 | 10.03% |
One key factor to rising TNUoS charges is the increasing number of renewable generators operating in the UK.
The majority of renewable generators are in remote, low demand areas or even offshore, due to the abundant space and available resources; this consequently means they are subject to disproportionally high TNUoS charges to send their produced electricity to distant, populated areas of high demand. The exact magnitudes vary, but generators in the far north of the UK may be subject to TNUoS charges up to seven times higher than a similar generator in the south of the country. With the country’s move towards green (renewable) power, and the resulting increased number of renewable generation sites, the charging imbalance discussed above has driven up TNUoS charges countrywide.
Another significant factor contributing to cost increases is due to maintaining and enhancing of the transmission network infrastructure for further renewable development. For example, Eastern Green Link 1 and 2, and Yorkshire Green are examples of such projects currently underway. The money to fund these projects must be recovered through higher TNUoS charges.
Rising HH TNUoS Demand (Triad) Charges:
Half Hourly customers face an additional charge according to demand during three busy Triad periods each year. These charges are applied locationally and, while zones 1-7 are excluded from this charge, charges on zones 8-14 have risen since last year, as shown below:
| Zone | Zone Name | 2023/24 Final (£/kW) | 2024/25 Final (£/kW) | 2025/26 Final (£/kW) | Percentage change from 2024/25 to 2025/26 |
|---|---|---|---|---|---|
| 1 | Northern Scotland | 0 | 0 | 0 | - |
| 2 | Southern Scotland | 0 | 0 | 0 | - |
| 3 | Northern | 0 | 0 | 0 | - |
| 4 | North West | 0 | 0 | 0 | - |
| 5 | Yorkshire | 0 | 0 | 0 | - |
| 6 | N Wales & Mersey | 0 | 0 | 0 | - |
| 7 | East Midlands | 0 | 0 | 0 | - |
| 8 | Midlands | 3.04689 | 2.37314 | 2.99096 | 26.03% |
| 9 | Eastern | 0.27252 | 0.82537 | 1.11075 | 34.58% |
| 10 | South Wales | 6.68980 | 4.50351 | 6.88504 | 52.88% |
| 11 | South East | 2.92853 | 3.85920 | 5.56824 | 44.28% |
| 12 | London | 4.37545 | 5.73267 | 7.40535 | 29.18% |
| 13 | Southern | 5.29062 | 6.86973 | 7.57017 | 10.20% |
| 14 | South Western | 7.64571 | 8.19892 | 10.12304 | 23.47% |
Tackling Rising TNUoS Costs:
The UK Office of Gas and Electricity Markets (OFGEM) has recently taken steps towards applying what it calls “a temporary cap and floor mechanism” to rising TNUoS (Transmission Network Use of System) charges. These changes are in response to uncertainty associated with projected future TNUoS charges and increases to TNUoS, both of which are raising concerns from potential investors in new generation.
Such concerns potentially disincentivise new renewable generation, thus threatening the government’s Clean Power 2030 Action Plan.
OFGEM laid out these concerns in an open letter to the National Energy System Operator (NESO) and moved to address them by proposing the cap and floor. Such a cap would place an upper limit on thenumber of credits a hypothetical, non-renewable generator in the South would receive, whilst also placing an upper limit on how much a remote renewable generator would be charged. The exact way OFGEM decides to implement this, and its results, remain to be seen.
NUS will issue further updates when available. Should you have any questions relating to TNUoS or non-commodity charges, please contact your NUS Consultant.
If you are an organisation that would like to understand how NUS can support in optimising your non-commodity charges, please contact us.