National Grid files £4.5bn transmission spend request with Ofgem

The proposals arrive via Ofgem's re-openers process, which allows network operators to request funding above the baseline set in a price control when system demands outpace original assumptions. National Grid argues that the current baseline, agreed under the RIIO-T3 (Revenue = Incentives + Innovation + Outputs, third transmission period) price control, is insufficient to meet accelerating connection demand from renewables, heavy industry, and data centres.

The £4.5 billion package covers transmission reinforcements, new low-carbon generation connections, support for large industrial loads, and resilience upgrades. It sits within National Grid's broader five-year capital programme of £70 billion across its UK and US networks. The company states the portfolio was shaped by whole-system analysis, asset health assessments, and delivery method reviews.

What this means for UK commercial energy buyers

Transmission investment of this scale feeds directly into the non-commodity costs on business electricity contracts, primarily through Transmission Network Use of System (TNUoS) charges, which are recovered from suppliers and passed through to customers. Ofgem's decision on these re-openers will influence TNUoS tariff-setting for future regulatory years. Buyers approaching renewals in 2026-27 and beyond should factor potential upward pressure on network cost components into their budgets.

Key items to track as Ofgem works through the review:

UK day-ahead baseload power over the last 12 months provides the wholesale backdrop against which any uplift in network charges will land for buyers.

• TNUoS tariffs for the RIIO-T3 period, where approved spend will ultimately land
• Ofgem's consultation timeline on the 25 individual re-opener submissions
• Connection queue reform progress at National Grid ESO, which interacts with the same capacity constraints driving this request
• Industrial and commercial demand charges for high-load sites seeking new or upgraded grid connections
• DESNZ clean power targets, which underpin the political pressure on Ofgem to approve grid build-out

For context, TNUoS already represents a material share of total electricity bills for many industrial and commercial sites. Any significant uplift approved through this process would compound cost pressures that buyers are already managing alongside wholesale volatility.

Ofgem will now consult before reaching a funding decision. The pace of that process matters: grid connection delays are currently cited by developers across generation, storage, and electrification as one of the principal barriers to Britain's clean energy transition. How quickly Ofgem moves, and what conditions it attaches to approval, will set the tempo for the network build-out over the next regulatory period.