How will the new TNUoS changes affect your business?

The National Energy System Operator (NESO) recently published its five-year view on TNUoS tariffs for 2026/27, and the result is simple. Electricity standing charge s for businesses will have a substantial increase come April 2026, with a continuous incline for the following years shown in the forecast.

This increase is primarily due to the scale required to invest in upgrading the grid to support the increased use of renewable energy sources. The TNUoS charges currently account for around 10% of electricity costs, and with the forecast rising to 94% from 2025/26 to 2026/27, this could significantly impact businesses' operational costs.

What is TNUoS?

'Transmission Network Use of System (TNUoS) charges pay for the high-voltage network that moves electricity across the country. Every business pays towards it through their electricity bill, usually within the standing charge or as a separate line on pass-through contracts. TNUoS is one of the non-commodity costs on your bill, the charges that have nothing to do with the wholesale price of the energy itself. These non-commodity costs have been growing steadily for years, and now make up a large share of what businesses actually pay.

Why are the charges rising?

In short, the grid is being rebuilt. Connecting new offshore wind farms, new nuclear, and new interconnectors means thousands of kilometres of new transmission infrastructure, and the investment is on a scale not seen in decades. TNUoS is how that investment gets recovered, so as the building programme accelerates, the charges rise with it.

TNUoS currently accounts for around 10% of business electricity costs. NESO's forecast shows the tariffs nearly doubling from 2025/26 to 2026/27, with further rises pencilled in through the rest of the decade. For a charge that most businesses have never looked at twice, that's a significant hit to operational costs.

There's a fairness point buried in this too: the costs of a greener grid are being loaded onto standing charges, which businesses pay regardless of how much energy they use. That makes it harder to dodge by simply consuming less, which is why contract strategy matters more than usual here.

How does your contract type affect what you'll see?

Pass-through contract: If you are on a pass-through contract, you will see the breakdown of the commodity and non-commodity costs. This meaning when these charges start to take effect, you will be the first to know exactly the difference in the new cost.

Fixed Contract: If you are in a fixed contract, you will not be able to forecast your total electricity usage. Until your first bill after the tariff comes into place.

What to look out for

You may think that being on a fixed contract protects you from the TNUoS tariff changes due in April 2026. However, most suppliers do not fix their TNUoS costs, so your standing charge will likely rise in line with the new changes.

If your contract runs until or beyond April 2026, make sure you read your terms and conditions carefully to check whether your supplier can reopen your fixed contract to reflect the updated TNUoS tariff.

The catch hiding in 'fixed' contracts

You might assume a fixed contract shields you from the April 2026 changes. However, most suppliers don't fully fix TNUoS within their fixed prices. Many contracts contain review or reopener clauses that let the supplier adjust prices when third-party charges like TNUoS change materially.

If your contract runs to or beyond April 2026, read the terms carefully. Look for wording about 'changes in law', 'third-party costs', 'industry charges', or price 'reopeners'. If those clauses exist, your fixed price can move. If you're quoted a genuinely fully fixed contract, expect the risk to be priced in. Since the supplier is taking the TNUoS gamble on your behalf and will charge for it.

Key dates to note

  • NESO's updated TNUoS forecast was due on 30th November 2025.
  • Final tariffs for 2026/27 were due by 31st January 2026.
  • The new charges take effect from 1st April 2026.

With the final tariffs now published, your regional numbers can be confirmed rather than estimated.

What should businesses do before the new charges come into play?

Now is also a good time to think about whether on-site renewable energy, like solar panels, could work for your business. Generating some of your own power could help you cut down on peak transmission charges and soften the impact of rising grid costs.

With the new tariffs coming into play in April 2026, there is no getting around it. The only thing you can do is time your contracts right and secure the most competitive rates. Staying ahead is really important if you want to minimise the risk of soaring high electricity bills.

How Purely can help

We can help review your contracts, confirm the type you have, and provide you with figures as to how much your site may face in April 2026.

Need quotes for the upcoming TNUoS changes or support with your energy bills? Get in touch!

Contact us at 0161 521 3400 or Info@purelyenergy.co.uk. Alternatively, you can get a quick quote.