United Utilities PLC unveiled plans for £13.7 billion of investment as it pledged the UK's biggest spill-reduction plan with aims to halve hosepipe bans.
The utility firm said this would drive significant regulated capital value growth at 8.7% per annum, equating to over 50% nominal across the period.
United Utilities said gearing at 58% provides flexibility to finance the full plan with average gearing of 65% over the asset management plan (AMP), based on Ofwat's weighted average cost of capital assumptions, and without assuming new equity.
Chief executive Louise Beardmore said: "What's clear is that we need to improve services for customers and the environment.
"That's why we are proposing the largest investment in water and wastewater infrastructure in over 100 years, with £13.7 billion planned between 2025 and 2030 to build a stronger, greener and healthier North West for everyone."
The company said its submission to Ofwat assumes that the programme is funded with equity and debt, with equity sized to maintain the current A3 rating with Moody's and A-senior unsecured debt rating with Fitch.
Adopting Ofwat's 'early view' cost of capital, United Utilities said its business plan assumes notional equity of £1.35 billion, out of a total capital requirement of around £5.2 billion. This gives rise to average gearing across the AMP of 63%.
Alongside the investment plans, the firm said current trading is in line with expectations.