A new report has uncovered that moving the UK’s Critical National Infrastructure (CNI) sectors from outdated analogue networks to digital infrastructure could deliver billions in benefits.

Released by BT and conducted by Assembly Research, the study finds a £3 billion net economic benefit that could be realised across five key sectors by 2040.

The research evaluated the costs, risks, and potential gains from digital migration across energy, water, health (NHS), emergency services, and local government, and accounted for the direct cost of upgrading, as well as the rising expense of maintaining legacy systems like the Public Switched Telephone Network (PSTN) and 2G mobile network.

Beyond the financial case, the economic modelling showed societal and environmental benefits by 2040, such as cutting 3.42 megatonnes of carbon emissions, freeing up 21 million hours of council staff time, and saving over 600,000 NHS staff hours.

Looking ahead, the benefits of digital migration are projected to bring significant improvements across the UK’s critical infrastructure. Digital networks for the energy sector can deliver improved resilience, help prevent outages, and enable more accurate demand forecasting – translating to an estimated £1.4 billion in savings.

Meanwhile, local governments – often under pressure to do more with less – stand to gain £486 million by modernising telecare systems and cutting the cost of maintaining ageing analogue equipment.

Emergency services could see fewer false alarms and improved call management, while in the NHS, digital transformation promises better call handling and more efficient emergency response.

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“For the first time, we’ve lifted the lid on legacy network migration and worked to understand the scope and scale of how key UK industries are still relying on aging fixed and mobile networks,” said Matthew Howett, founder and CEO of Assembly Research.

“Our research found that while the energy and water sectors are already well into their migrations, it’s vital that others follow to avoid growing costs and missed efficiencies.”

Jon James, the CEO of BT Business, added: “This research sends a clear message: delaying the shift to digital carries a real cost to public services, the environment and the wider economy.”

“Legacy systems are becoming increasingly unreliable, and the case for action is urgent. BT is committed to guiding the UK’s critical national infrastructure sectors through this upgrade with the resilience and support they need.”

The UK’s transition to digital connectivity is a major infrastructure programme endorsed by Ofcom and the UK Government.

The PSTN is set to be fully retired in January 2027, with businesses and public services urged to complete migrations by 2025 to avoid disruption.