TNUoS charges: why high voltage (HV) sites pay more from 2026, and what to do

What changed in April 2026

TNUoS charges pay for the national transmission network. The largest part for most business sites, the residual charge, is a fixed amount per site per day. The National Energy System Operator (NESO) charges it to suppliers, and how it shows on your bill depends on your contract: as a separate line, inside a standing charge, or built into your rates.

For 2026/27, NESO says the residual charge is on average 65% higher than in 2025/26, reflecting higher allowed transmission revenue under Ofgem's 2026 to 2031 price control (RIIO-3). NESO's current forecasts show it continuing to rise to 2031, and an updated five year view is due on 8 October 2026.

Because it is charged per site rather than per unit, using less electricity does not reduce it. What decides the charge is the band a site falls into, set by its connection voltage and agreed capacity. Sites without an agreed capacity are banded on annual consumption.

Why HV sites are most exposed

• HV sites are charged on a separate set of bands, and most of them cost far more per day than low voltage (LV) bands. In 2026/27 the HV residual runs from £31.84 to £528.91 per site per day, against £5.80 to £38.18 for LV sites with an agreed capacity.
• The band thresholds were reset in April 2026 and stay fixed until 2031. A site generally keeps its band for that period. Under the reallocation rules Ofgem approved for these bands, a site is only reassessed in specific cases, such as its agreed capacity or consumption changing by more than 50%, a change in its connection voltage, a move to a different category of site, or a successful dispute over its allocation.
• The gaps between HV bands are large. On NESO's 2026/27 tariffs, moving from band HV1 to HV2 adds about £31,000 a year, and from HV3 to HV4 about £125,000.

The options

• Check your band. First, confirm what band each site is in, on what basis, and whether the agreed capacity behind it is still right.
• Agreed capacity review. A formal capacity reduction can lower capacity charges. Before 2031 it generally only moves a site to a lower residual band if the agreed capacity falls by more than 50% from the figure used for the allocation. It must be done carefully so supply is not put at risk.
• Metering relocation from HV to LV. For some sites, moving the point of metering from the high voltage side to the low voltage side changes the set of bands the site is charged in. For 2026/27, the HV3 residual is £185.42 a day, against £38.18 for the highest LV band. It is an infrastructure change, involving transformers and switchgear, and needs a feasibility study, design and build. On some sites the numbers work; on others they do not.
• On site generation and flexibility. Reducing peak demand and capacity requirements over time can lower other capacity based charges, and may support a lower band at a future reallocation.

What a proper feasibility study looks at

Relocating the metering from HV to LV changes the TNUoS band, but it is not a free saving. Some costs move in the other direction, and a credible study nets them off first:

• Distribution charges change. An LV metered site pays LV distribution rates, which are generally higher per unit than HV rates.
• Losses still have to be paid for. With HV metering, transformer losses are already recorded by your meter. If the meter moves to the LV side while you still own the transformer, the metered volumes have to be adjusted for those losses. If the network operator takes over the transformer, losses are recovered through the line loss factors for your new connection voltage.
• Network operator costs and consent. The change usually needs a network operator or independent network operator to adopt the arrangement, with a technical submission, design and possibly new equipment.
• Physical works. Metering, current transformers, cabling and protection settings, with a survey and a technical pack before anything is priced firmly.

The output you should expect is a net figure over the price control period, an indicative payback, a clear view on whether to proceed, and a list of the information still needed. If a proposal only shows the TNUoS saving, it is worth asking what has been left out.

How metering relocation works

Many high voltage sites own the transformers, switchgear and cables between the grid connection and their buildings. Relocation moves the point of metering to the low voltage side of that equipment, so the site is charged in a low voltage band.

This is usually done through network adoption, where a licensed independent network operator takes over the high voltage equipment. Where adoption applies:

• Little or no upfront cost. Upgrades needed to bring the equipment up to standard can often be included in the adoption.
• Less risk on your books. Responsibility for maintaining ageing high voltage equipment, including faults and future upgrades, passes to the operator.
• Minimal disruption. Switchover works are planned around your operations and can be carried out out of hours.

What the process looks like

• Site audit and feasibility, around 2 to 3 weeks. Data gathering, eligibility check, an initial savings view and a go or no go recommendation.
• Technical design, around 2 to 3 weeks. Options appraisal, outline design, scope, programme and risks.
• Agreements, around 3 to 4 weeks. Engaging the network operator, adoption and connection agreements, and new meter registrations.
• Site works, around 6 to 12 weeks. Metering change, any planned shutdown, testing and commissioning.
• Afterwards. Checking the new charges appear correctly on your bills.

Timings vary by site. To start a feasibility review we usually need a recent single line diagram of the site's electrical network (or the nearest equivalent), recent bills or consumption data, your connection agreement and access for a short site visit.

Judge it on the net figure

A good assessment sets the reduction in transmission charges against the higher distribution charges and transformer losses that come with low voltage metering, and shows the net result over the price control period. We have seen some strong examples, with projected net savings running into six figures for larger sites, but the result varies a lot from site to site.

How Energy Planner helps

• Identify the band and the charge on each site from your bills and connection agreements.
• Model the options and what each is likely to mean over the price control period.
• Manage capacity reviews with the network operator.
• Where relocation looks worthwhile, bring in specialist engineers for feasibility, design and build.
• Check the new charges appear correctly on your bills afterwards.

Common questions

Can I reduce TNUoS charges by using less electricity?
Not the residual part. It is a fixed charge per site per day based on your charging band, so it does not fall with consumption. The band itself is what you need to look at.

Can my site move to a lower charging band?
Sometimes. Bands are set by connection voltage and agreed capacity, or by consumption where there is no agreed capacity. Before 2031, a band change generally needs a change of more than 50% in capacity or consumption, or a change in connection voltage, and each option needs assessing properly.

Does metering relocation cost anything upfront?
Often very little or nothing. Where the high voltage equipment is adopted by a licensed network operator, the works and upgrades can usually be included in the adoption. A feasibility review confirms this for your site.

How long does it take?
Typically around three to five months from the first site audit to switchover, depending on the site, the equipment and the network operator.

Is metering relocation right for every HV site?
No. It depends on the site's load, the existing equipment and the cost of the works against the saving over the price control period. A feasibility review comes first.

Sources: NESO final TNUoS tariffs 2026/27, NESO 2026/27 tariffs webinar and Ofgem DCP410 decision. This page is general information based on published charging methodologies and tariffs as at October 2026, not advice on your specific sites. Charges, bands and forecasts change, and any physical works need a proper feasibility study, so it is worth confirming the position for your sites before making a decision.