TNUoS is rising 60%. Here’s what that actually means for your electricity bill — and what to do before April.
From April 2026, the transmission charges embedded in your electricity bill are set to jump by more than 60% — rising from £18.9/MWh to an estimated £31/MWh as Ofgem’s RIIO-3 price controls take effect. For businesses on pass-through contracts, there is no buffer. The increase lands on your bill immediately, stacking on top of distribution, balancing, and other non-commodity costs that already add around £25–26/MWh to what you pay. This is not a marginal shift. For a mid-sized manufacturer or distribution centre running several GWh per year, the arithmetic is sobering — and the window to act is narrowing.
What ss driving the increase — and why it matters strategically
TNUoS — Transmission Network Use of System charges — is how National Grid ESO recovers the cost of maintaining and expanding the high-voltage transmission network. The sharp increase from April 2026 is not an anomaly; it is a deliberate policy signal. RIIO-3 is designed to fund the grid infrastructure required to deliver Clean Power 2030: new interconnectors, reinforced substations, and the expanded transmission capacity needed to integrate offshore wind at scale. The charges are, in a real sense, the cost of the energy transition passed directly to large electricity consumers.
Understanding this framing matters because it changes how businesses should respond. This is not a one-off spike that will self-correct. The investment programme underpinning these charges runs across the next regulatory period and beyond. Businesses that treat TNUoS as a procurement problem to be solved by switching supplier or locking in a fixed contract will find that fixed contracts simply price in the forecast increase. The more durable response is operational: reduce the volume of electricity you consume during the periods that attract the highest transmission charges, and shift flexible load away from peak demand windows.
The operational lever most businesses are not yet pulling
TNUoS charges are calculated using a Triad methodology — your liability is heavily influenced by your consumption during the three half-hour settlement periods of highest system demand in the winter months. Businesses that can reduce or shift load during these windows can materially reduce their transmission charge exposure. In theory, this has been true for years. In practice, most energy managers lack the real-time visibility and automated control capability to act on it consistently.
This is precisely the gap that AI energy management platforms are designed to close. At Heliotec, our platform continuously monitors consumption across sites, forecasts Triad risk periods, and — where flexible assets are in place — can automatically adjust load in response. The same capability that supports Triad avoidance also surfaces broader consumption inefficiencies: equipment running outside operating hours, processes drawing more power than their baseline suggests they should, HVAC systems cycling against themselves. For manufacturers, logistics operators, and large retail sites, these are not trivial findings. They translate directly into MWh reductions that compound across every cost component on the bill — including TNUoS.
What to do before April
Three steps are worth prioritising now. First, review your contract structure. If you are on a pass-through arrangement, understand exactly which charges are floating and model the April impact at your current consumption volumes. Second, investigate exemption and relief schemes. The British Industry Supercharger and Energy Intensive Industry exemptions exist specifically to limit transmission charge exposure for qualifying businesses — many eligible organisations have not claimed them. Third, and most importantly, establish a consumption baseline across your sites. You cannot shift or reduce what you cannot see. Deploying sub-metering and intelligent monitoring before April means you will enter the new charging year with the visibility needed to act — rather than simply absorbing the increase.
The broader view
TNUoS is one component of a non-commodity cost stack that has been rising steadily and will continue to do so as the grid modernises. The businesses that manage this well over the next three to five years will not be those with the best procurement contracts — they will be the ones with the best operational intelligence. April 2026 is a useful forcing function. The 60% transmission charge increase is large enough to command boardroom attention and create the mandate for change. The question is whether that attention translates into lasting capability, or a one-off contract review that leaves the underlying exposure intact.
If you are working through the implications for your sites and want to understand what load shifting or consumption reduction could mean in hard numbers, we are happy to work through it with you.