Non-commodity costs - the charges on your bill that aren't the energy itself - now make up over half of the average UK business energy bill. TNUoS is one of them. It's been on your bill for years, alongside dozens of other levies, and April 2026 is when it got significantly more expensive. Regulators upped the rate by around 60%, and most suppliers passed that straight through to their customers.

Here's what's actually going on.

What TNUoS is

TNUoS stands for Transmission Network Use of System. It's a levy that funds the UK's high-voltage electricity network - the pylons, cables and substations that carry power from generators across the country and into local distribution networks. Without that infrastructure, electricity produced by a wind farm in Scotland couldn't reach a warehouse in the Midlands.

NESO, the National Energy System Operator, sets the TNUoS rates every April. Every business connected to the UK grid pays it. It isn't a supplier fee - it's an industry-wide charge that all suppliers collect and pass on. It appears on your bill as ‘TNUoS Residual Banded Charges’ .

How your rate is set

Not every business pays the same. NESO assigns each site to a band based on its Maximum Import Capacity - the contractual ceiling on how much power that site can draw from the grid. The higher that ceiling, the higher the band, and the higher the charge.

What changed in April 2026

NESO updated the rates this April, and the increase has averaged around 60% on last year's figures. That's a meaningful jump in a fixed cost that arrives with little warning and no negotiation. It also doesn't arrive alone — Nuclear RAB and the Climate Change Levy (CCL) have also increased this April, making it a particularly sharp moment for business energy bills across the board.

What most suppliers did

Most suppliers passed the increase through to customers. Some opened up mid-term contracts to do it, invoking clauses that allow charges to be adjusted when industry rates change. For businesses on those contracts, the cost landed directly - and in many cases, without much warning.

What tem did

For every customer on a contract agreed before October 2025, TNUoS was included as a standing charge. That's what customers agreed to pay - and that's what they'll pay. tem is absorbing the TNUoS increase in full for the remainder of their current contract. Not a penny more.

Many of those contracts included a variation clause that would have given tem the legal right to pass the increase through. We chose not to use it. Customers agreed to a standing charge, and that's the commitment we're honouring - regardless of what the small print would have allowed. We don't think landing a significant cost on a business - especially right now - is the fair thing to do.

What about customers on newer contracts?

For customers who signed after 14 October 2025, TNUoS is already set up as a passthrough charge - confirmed clearly on their quote from day one. For the majority of these customers, the new rate has come in lower than the forecast used when they contracted, so they'll see a decrease in their TNUoS Residual Banded Charge from May. A smaller number will see an increase. For those customers, tem is actively prioritising them for P442 - a regulatory scheme that, when matched, reduces certain industry non-power costs (NCCs) on their bill and will help offset any impact they’ve seen.

What this means going forward

When existing customers renew, TNUoS moves to a passthrough arrangement on new contracts - as it does across the industry. There's full transparency on what it is and how it moves.

If your business wants to reduce its TNUoS exposure over time, the most direct route is rebanding - which becomes possible if your peak demand falls and your Maximum Import Capacity can be renegotiated downward. It's also worth understanding how NCCs work more broadly, and how schemes like P442-backed Exempt Supply can reduce certain ones on your bill.

NESO will set new TNUoS rates again next April. The rate will move - it always does. The question worth asking before you sign your next contract is what your supplier will do when it does.