The National Energy System Operator (NESO) has published its latest Five-Year View of TNUoS (Transmission Network Use of System) tariffs. The headline is clear: a typical consumer could face an average increase of about 38% in total TNUoS costs in 2026/27. The main driver is higher demand residual revenues. Your actual impact will depend on location, connection, and consumption, so now is the time to budget and optimise.

The Forecast

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• Average rise: about 38% in total TNUoS for a typical user in 2026/27

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• Drivers: higher revenue recovery for transmission owners, increased grid investment, and slower progress on long term market reforms. Demand residuals carry much of the uplift

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• Locational effects: your TNUoS zone and usage shape exposure

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• Regional guide (illustrative): South West about 40%, London about 35%

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• Outlook: volatility likely until REMA outcomes take effect, currently targeted around 2029

Side by side snapshot

What are TNUoS charges?

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• Purpose: TNUoS pays for building, operating, and maintaining Great Britain’s high voltage transmission network

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• Who sets them: Ofgem sets the framework that allows transmission owners to recover allowable revenues through TNUoS, which suppliers and generators pay before costs flow to end users

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• Principle: user pays. Charges reflect the cost of transporting electricity across the national grid, with locational signals to encourage efficient use

Why are they increasing?

Rising revenue needs

Transmission owners must recover higher allowed revenues to operate and reinforce the system. Some historic offsets, such as prior year tax allowances, are reducing, which increases the net amount to collect.

Investment in the network

More renewable generation is connecting far from demand centres. Moving clean power to where it is used requires new lines, substations, and system capability, which adds cost.

Lack of near term reforms

The Review of Electricity Market Arrangements (REMA) is still in progress. Until changes are implemented, likely close to 2029, the current framework must manage significant cost shifts.

Demand residuals doing the heavy lifting

For 2026/27, demand residual revenues account for a large share of the uplift, so many end users will feel the effect.

When will the increase happen?

The material change is expected in the 2026/27 charging year, with further evolution through the decade as investment and policy develop.

How will this impact consumers?

Regional variations

TNUoS is locational, so percentage changes vary by zone:

Your exact outcome depends on zone, connection voltage, metering class (HH or NHH), agreed capacity, and coincidence with system peaks.

Larger users

For C&I sites, TNUoS is a meaningful operating expense. Multi site portfolios that span zones can see very different outcomes, which creates both risk and optimisation opportunities.

Planning timeline

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• Now to Q1 2026: build site level exposure models, set budgets, identify quick wins

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• 2026/27: expect the step change, monitor monthly, adjust operations

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• 2027 to 2030: continued grid build out, refresh forecasts annually

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• Around 2029: REMA outcomes begin to reshape incentives and charging signals

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How Nationwide Utilities can help

We support C&I customers that want to quantify exposure, control it, and reduce it.

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• TNUoS diagnostics that include zonal mapping, HH data analysis, and site level bill impact modelling

• Capacity and profile optimisation from paperwork through to plant changes

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• Business cases for on site assets such as solar, storage, and controls, with measured benefits

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