The National Audit Office (NAO) has said that households face rising energy bills unless the electricity grid is upgraded urgently to carry more renewable generation, in a report published on 11 September 20261.
The NAO said the grid cannot carry enough electricity "from where it is produced to where it is needed", which forces the National Energy System Operator (NESO) to keep supply and demand in balance by paying wind farms to turn off and gas plants to turn on1. These payments are known as constraint costs and are passed through to household bills. In the 2025-26 financial year they totalled around £1.9bn, and the NAO said they could increase to £7.8bn by 2030 without concerted action from NESO1.
Ofgem estimates that £70bn of investment is required in the grid between 2025 and 2031, which is already expected to increase the network charges consumers pay by £60 by 2030. The NAO said that investment would also save consumers £30 overall compared with the increased constraint costs if projects are not accelerated1.
The report describes the upgrade timetable as "very challenging". Of the 80 projects NESO identified as necessary in its 2024 Clean Power advice, 64 are ongoing, but most are at an early stage of development and are not expected to be connected by the dates NESO considers optimal for keeping constraint costs down between now and 2030. Many also face significant risks to their current forecast delivery dates1.
NESO identified three projects in particular that needed to be accelerated to meet Clean Power 2030, and eight others where acceleration would also reduce constraint costs. The NAO said there has not been a "significant acceleration" in any of these projects so far1.
"Value for money now depends on delivery. Failure to implement these necessary grid upgrades will hamper economic growth as well as increase consumer bills."
The connection queue remains heavily oversubscribed. NESO implemented changes to the approval process for connecting new facilities last year in an effort to curtail "zombie" energy projects, which are typically stalled for financial or regulatory reasons but hold a place in the queue ahead of projects that are ready to go1. The old queue for grid access grew tenfold in five years, reaching over 700GW, around four times Britain's projected need by 2030, and some green energy projects have to wait for up to a decade before they can be brought online1.
| Measure | Figure |
|---|---|
| Constraint costs, 2025-26 | around £1.9bn |
| Constraint costs by 2030, without action | £7.8bn |
| Grid investment required, 2025 to 2031 | £70bn |
| Expected increase in network charges by 2030 | £60 |
| Saving from accelerating projects | £30 |
Why it matters for households
Constraint costs are ultimately recovered through bills, so the pace of grid delivery feeds directly into what a home pays for electricity, whether or not that home generates its own power. The NAO's figures set the scale: a rise from around £1.9bn to £7.8bn in constraint costs by 2030, against a £60 expected increase in network charges that is partly offset by a £30 saving if projects are accelerated1.
For a household, the practical effect is that the cost of the wider national supply system sits alongside whatever a home does on its own. The NAO's findings concern transmission capacity and the queue for connections, not the wires or meters at a property, so they do not change what an individual home can control. The distinction between system-level costs and household-level energy security and household independence is the relevant one here: constraint costs are set by how the grid is run, while a home's own exposure depends on how much electricity it draws and when.
The report also touches on the connection queue, which governs how quickly new generation can be built. The queue reached over 700GW, around four times Britain's projected need by 2030, and some projects wait up to a decade1. Slower connection of new capacity keeps the system more reliant on the balancing payments that feed into bills.
What happens next
The NAO said there has not been a "significant acceleration" in any of the three projects NESO identified as needing to be accelerated for Clean Power 2030, or in the eight others where acceleration would reduce constraint costs1. Of the 80 projects NESO identified as necessary in its 2024 Clean Power advice, 64 are ongoing, with most at an early stage of development1.
National Grid will invest £1.2bn through its UK supply chain partners to deliver upgrades across 1,000km of overhead line routes1. No further dates for specific projects have been reported.