Data centre expansion could push another 10,000 London households into fuel poverty through higher energy bills under high-growth projections, the climate campaign group Global Action Plan has warned.

The group estimates that additional demand on Britain’s energy system from new data centres could add £88 to the average household energy bill. Its head of campaigns, Oliver Hayes, told the London Assembly Environment Committee that 77,000 British households could enter fuel poverty, with early regional analysis putting London’s share at about 10,000. Those already in fuel poverty would also become poorer, he said.

These are projected consequences of high growth, rather than recorded increases. The warning concerns how expanding digital infrastructure could affect households through its demands on shared electricity and water systems.

Data centres are concentrated in and around London partly because of their proximity to the City’s financial hub. Existing clusters attract further development, reinforcing that concentration.

Green Party leader and Assembly Member Zack Polanski called for a brake on construction, arguing that higher bills would compound the pressures of low wages. He said rising emissions threatened climate targets and that data centres should not take precedence over urgently needed homes.

Water supply creates a separate constraint. Jon Chappell, deputy director of Water UK, told the committee that extra summer consumption would require larger service reservoirs and treatment works because systems must meet the year’s highest demand.

If every forthcoming data centre matched the least efficient existing facility, he estimated, Britain would need another 77 million litres of water daily, equivalent to three London boroughs. That estimate depends on the stated efficiency assumption. Chappell said water shortages already prevented housebuilding and business expansion in parts of eastern and south-eastern England.

Rory Murphy, a University of Exeter research associate, highlighted indirect consumption. He cited 66 billion litres used directly to cool US data centres in a given year, alongside 800 billion litres associated with keeping their servers running.

The Mayor of London has commissioned a study into the implications for the capital’s water supply. Responding last year to Labour Assembly Member James Small-Edwards, he stressed that cooling technologies vary: some require water, while others use air or non-water systems, with considerably different impacts. Earlier this year, he called for a comprehensive London plan addressing water and grid pressures, including what other activities those demands might displace.

The draft London Plan supports data centres in suitable locations in principle, but makes approval conditional on available water and electricity capacity. That leaves capacity, rather than support in principle alone, as the crucial planning test.