TNUoS Charges Nearly Doubled from April 2026. What RIIO-3 Means for Your Transmission Charges.
Insights
Data Analyst
TNUoS fixed charges rose 40-80% for most businesses from 1 April 2026. A typical small business pays around £500 more per year.
From 1 April 2026, transmission charges got significantly more expensive. TNUoS fixed charges rose 40-80% for most businesses under the new RIIO-3 price control. For a typical small business, that's an extra £500/year.
What's Changing
The TDR (Transmission Demand Residual) is a fixed annual charge based on your connection type — it doesn't scale with how much electricity you use. Here's what businesses pay from April 2026:
Source: NESO published TNUoS tariff tables. Annual fixed charges by TDR band.
These are fixed annual charges — a site using 50,000 kWh pays the same TDR as one using 1,000,000 kWh if they're in the same band.
Band Thresholds Are Changing
RIIO-3 also shifted the band boundaries. The LV Band 1 threshold rose from 80 kVA to 90 kVA. If your site's average agreed capacity over the allocation window (1 May 2022 to 30 April 2024) was between 80-90 kVA, you dropped into a lower band automatically on 1 April 2026, saving over £2,100/year.
That allocation holds to 31 March 2031 (DCUSA Schedule 32 ¶4.5). Our Capacity Optimiser shows the band your site holds and the kVA thresholds either side.
Why Is This Happening?
RIIO-3 is Ofgem's new price control period for transmission, running April 2026 to March 2031. The step-change reflects investment in grid reinforcement for renewables and electrification.
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