BT has unveiled new economic modelling conducted by Assembly Research, emphasising the substantial financial, societal, and environmental advantages of upgrading the UK’s Critical National Infrastructure (CNI) sectors from outdated analogue systems to modern digital networks.

The study estimates that by 2040, a net economic benefit of approximately £3 billion could be realised across five key sectors, including energy, water, healthcare, emergency services, and local government.

The research analysed the costs, risks, and potential gains associated with digital migration, considering the expenses related to infrastructure upgrades and the escalating costs of maintaining legacy systems such as the Public Switched Telephone Network (PSTN) and 2G mobile networks, both of which are increasingly difficult to support. Data from Ofcom highlights a 45% rise in resilience incidents on the PSTN, underscoring the urgent need for modernisation.

Beyond the financial implications, the modelling reveals significant societal and environmental benefits that could be achieved by 2040. These include preventing around 750,000 unnecessary ambulance trips annually, which equates to over 100 avoided journeys each day. Additionally, the transition could free up approximately 12 million hours of council staff time — enough for around 6,500 full-time staff to work for a year — and save over 600,000 NHS staff hours, comparable to the annual workload of 350 full-time employees. The study also projects that moving away from legacy fire alarm systems could prevent up to 280,000 false fire service callouts each year, equivalent to about 54 false alarms daily.

Furthermore, the shift could reduce carbon emissions by 3.42 megatonnes, the equivalent of powering every home in Birmingham for a year.

Looking ahead, the benefits of digital migration are expected to enhance resilience and efficiency across the UK’s critical infrastructure. For the energy sector, digital networks could bolster resilience, prevent outages, and improve demand forecasting, leading to estimated savings of £1.4 billion. The water industry could see efficiencies worth £771 million through smarter network monitoring and reduced electricity consumption. Local governments stand to benefit by modernising telecare services and reducing maintenance costs on aging analogue systems, saving around £486 million. In healthcare, digital transformation promises more efficient emergency call handling and response times, while emergency services could experience fewer false alarms and more targeted, rapid responses.

“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,” said Jon James, CEO of BT Business.

“For the first time, we've examined the scope and scale of how vital UK industries still depend on aging fixed and mobile networks. While sectors like energy and water are already progressing with their migrations, it’s crucial that others follow suit to avoid rising costs and missed efficiencies,” said Matthew Howett, Founder and CEO of Assembly Research.

The UK’s transition to digital connectivity is a key national infrastructure initiative supported by Ofcom and the government. The PSTN is set to be fully retired by January 2027, with businesses and public services urged to complete their migrations by the end of 2025 to prevent last-minute disruptions. Despite significant progress — BT migrated nearly 300,000 legacy PSTN business lines in 2024 — many CNI providers still rely on aging analogue systems. While some countries like Germany and Spain are close to completing their migrations, others such as Italy, Portugal, and France are actively advancing their efforts. If the UK does not accelerate its migration pace, it risks falling behind its international counterparts.