Water companies have set out business plans including cuts to bills for millions of customers across England and Wales.
Severn Trent and United Utilities intend to cut their bills ben five percent and 10.5 percent respectively, while South West Water will offer its customers shares in the business.
Thames Water said it plans to leave its bills unchanged.
Water companies are required to submit business plans to the regulator, Ofwat, every five years on topics that include customer service, leaks, wastewater and bills.
Ofwat will publish an assessment of each company’s plan in January 2019.
Ofwat senior director for strategy & planning, John Russell, said: “We’ve reached a key milestone in our price review process. From now until January 2019, we’ll pore over each and every business plan and we’ll be looking for evidence that they are robust, ambitious and, crucially, that they have been shaped by customers.
“All companies have had an opportunity to develop high-quality plans, but where plans aren’t sufficiently ambitious or stretching, we’ll step in to protect customers and the environment.”
Thames Water, the UK’s largest water company, said that while bills would be flat over the five-year period, it intended to invest £2.1bn to "boost resilience and reduce leakage" after it was fined £120m in June over leakage failures.
In the North West of England, customers of United Utilities are being promised a 10.5 percent reduction on average bills in real terms and 250,000 fewer households in water poverty by 2025.
Severn Trent said the five percent fall it was promising its 8.1 million customers was the largest in two decades. Around 200,000 customers at its Welsh arm Hafren Dyfrdwy Cyfyngedig, will incur bill rises of 2.2 percent, although it added this was the smallest rise in Wales.
At South West Water, average customer bills are set to fall by 11 percent and by nine percent at its Bournemouth Water arm by 2025.
In what it described as a “first of its kind” proposal, South West Water put forward a plan to offer its customers a stake in the business from 2020. It includes the prospect of meetings where customers can cast votes. Customers could be given an option – alongside bill reductions, rebates and reinvestment – to have shares in parent company Pennon or a stake in South West Water itself.
Anglian Water said its bills would rise, but by less than one percent. East Anglia receives just two thirds of the national average rainfall.