Published 6 March 2026
Changes to electricity network charges and the introduction of the Nuclear Regulated Asset Base (nRAB) Levy are creating additional considerations for UK businesses comparing electricity contracts.
From 1 April 2026, revised Transmission Network Use of System (TNUoS) charges have increased costs for many electricity supplies. Meanwhile, the nRAB Levy, introduced in November 2025, is helping fund the development of new nuclear generating capacity.
Although these costs affect electricity suppliers across the market, the way they are incorporated into business electricity contracts and bills can differ.
As a result, an electricity quotation with a lower standing charge and unit rate may not necessarily represent the lowest overall cost.
Understanding how these charges work, and whether they are included within a supplier's quoted prices, is increasingly important when comparing business electricity contracts.
Transmission Network Use of System (TNUoS) charges contribute towards the construction, maintenance and reinforcement of Great Britain's high-voltage electricity transmission network.
These charges are calculated and published by the National Energy System Operator (NESO) under the industry's regulated charging arrangements. Electricity suppliers recover the associated costs through their pricing and billing arrangements.
The network investment being funded includes:
As Great Britain's electricity system evolves, substantial investment is required to ensure the transmission network can accommodate changing patterns of generation and consumption.
The revised TNUoS tariffs introduced on 1 April 2026 included increases in the fixed residual charges applicable to many electricity supplies.
The residual element of TNUoS is recovered through fixed charges rather than being directly linked to the amount of electricity consumed.
Depending on how their supplier structures its pricing, businesses may therefore see:
Importantly, TNUoS tariffs are reviewed annually, with revised tariffs normally taking effect each April. This means suppliers must account for potential changes in network costs when pricing electricity contracts that extend across multiple charging years.
However, an increase in the underlying TNUoS tariff does not automatically mean a supplier is entitled to increase an existing customer's contracted rates. That depends on the terms of the electricity supply agreement.
The Nuclear Regulated Asset Base (nRAB) Levy is a government-backed funding mechanism designed to support the development of new nuclear power stations, initially Sizewell C.
Under the RAB model, certain costs can be recovered during the construction period, rather than relying entirely on revenue generated once a nuclear power station becomes operational.
The levy applies through electricity suppliers, which recover the relevant costs from customers, subject to applicable exemptions.
Unlike TNUoS, which relates to the electricity transmission network, the nRAB Levy contributes towards the financing of new nuclear generation.
The underlying nRAB levy rate is reviewed and published quarterly, creating an additional consideration for suppliers when setting fixed electricity prices over longer contract periods.
Some suppliers may build forecast nRAB costs into their contracted unit rates, while others may recover relevant charges separately or through contractual adjustment provisions.
The important question for customers is not simply whether the nRAB Levy appears on their bill, but whether it is already included in their agreed electricity price or represents an additional recoverable cost.
One of the most confusing aspects of TNUoS and nRAB charges is that suppliers do not necessarily recover them in the same way.
Broadly, suppliers may adopt different approaches, including:
These approaches can have materially different implications for customers.
For example, one supplier may include forecast network and levy costs within a higher initial quotation, while another may offer lower headline rates but recover certain costs separately.
Furthermore, a separately itemised charge does not necessarily mean the customer is paying more than originally agreed. The charge may simply be displayed separately for billing transparency.
Equally, the absence of a separate charge does not automatically guarantee that all associated costs are fixed for the contract term.
The supplier's product-specific contractual terms ultimately determine which charges are included, which are additional, and whether any amounts can change during the agreement.
Not necessarily.
A business electricity contract may specify fixed unit rates and a fixed standing charge while still containing provisions allowing certain additional charges or adjustments.
These provisions may relate to changes in regulated network costs, government schemes or other third-party charges.
This creates an important distinction between a contract offering fixed headline rates and one that provides greater certainty over the customer's total electricity costs.
For businesses seeking budget certainty, it is essential to establish whether TNUoS and nRAB costs are:
These distinctions are particularly important for contracts extending over two or three years, during which underlying network tariffs and levy rates may change.
When comparing business electricity quotations, it is natural to focus on the standing charge, unit rate and projected annual cost.
However, those figures may not always provide a complete comparison if suppliers treat certain non-commodity charges differently.
A supplier offering the lowest headline rates may ultimately prove more expensive if additional TNUoS, nRAB or other recoverable charges are excluded from the quotation.
Conversely, a supplier quoting slightly higher rates may provide greater price certainty if those costs have already been included.
Neither approach automatically makes one supplier cheaper than another.
The most meaningful comparison is the total expected contract cost, taking account of all applicable charges and any provisions allowing those costs to change during the contract term.
Climate Change Levy (CCL) and VAT are generally treated separately from quoted net electricity costs and are applied according to statutory rates and eligibility rules.
TNUoS and nRAB are different because their underlying costs are determined through industry charging and levy arrangements, while the way those costs are recovered from an individual customer depends on the supplier and the relevant contract.
Before accepting a business electricity quotation, customers should establish exactly which charges are included in the proposed contract and whether any additional costs may arise.
In particular, businesses should seek clarification on:
Where the position is unclear, written confirmation should be obtained before entering into a new agreement.
Businesses receiving notices of additional TNUoS or nRAB charges during an existing contract should also review the relevant contractual provisions before assuming that the increase is either unavoidable or incorrectly applied.
TNUoS and Nuclear RAB charges are legitimate components of the wider electricity supply cost, but their treatment within individual business electricity contracts can differ.
For customers, this makes it increasingly important to look beyond headline standing charges and unit rates when comparing suppliers.
A quotation should clearly identify what is included, what is excluded and which charges may change after the contract begins.
Without that information, businesses cannot be confident that competing electricity quotations are being compared on a genuinely like-for-like basis.
