NAO warning on grid upgrades lagging renewables: delivery risks for UK project teams
Reviewed by Joe Ashwell

First reported on The Construction Index
30 Second Briefing
Grid upgrades are lagging behind the rapid build-out of renewables, with the National Audit Office warning that transmission constraints could cost up to £7.8bn in 2030 if the current programme is not accelerated. Ofgem estimates transmission owners must invest up to £70bn in the next five years, with NESO calling for a further £89bn beyond 2030, yet many of the 64 upgrade projects are still at early development stages and face land-use approval delays of up to three years. Frequent cancellation or rearrangement of planned outages, plus supply chain and skills bottlenecks, signal prolonged curtailment payments to wind and increased reliance on gas plant dispatch.
Technical Brief
- Much of the existing transmission network dates from 1950s–1970s, optimised for large centralised fossil stations.
- DESNZ’s 95% clean electricity target by 2030 drives need to repurpose and reinforce legacy corridors.
- NESO currently resolves transmission bottlenecks by paying wind to curtail and gas plant to increase output.
- A 2015 shift by DESNZ to a market-led, non-spatial planning model is identified as a root cause.
- NAO flags 64 live transmission upgrade schemes, with a high proportion still in early development phases.
- Land-use and planning approvals are adding up to three years to individual grid project timelines.
- As many as two-thirds of planned grid outage windows for upgrade works are cancelled or rescheduled.
- NAO calls for stronger delivery oversight, transparent progress monitoring, and more robust regulatory cost scrutiny.
Our Take
With as many as two‑thirds of planned outages reportedly cancelled or rearranged, contractors and network operators in the UK can expect tighter outage planning regimes and possibly new regulatory incentives from Ofgem to de‑risk delivery windows on the 64 live grid upgrade projects.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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