Southern Water has secured additional equity investment to fund its ambitious £6 billion AMP8 investment programme over 5 years.

This investment programme includes:

• the complete rebuilding of the utility’s 5 largest water treatment plants
• new nutrient treatment at 40% of all treatment plants to improve river quality treatment plants
• new water supply and resilience measures including the new reservoir being constructed with Portsmouth Water and 5 new water recycling plants, and overflow reductions at 170 sites.

Overall, this will provide additional capacity and resilience in response to new legislation and regulatory targets and to support forecast population growth, as well as improvement in services for customers.

In July 2025, Southern Water announced it was seeking to raise up to £1.2 billion of equity to support its 2025-30 AMP8 investment programme. This followed circa £1.65 billion of equity that was invested into the group during the previous 2020-25 AMP7 regulatory period.

The £1.2 billion comprised an initial £655 million of binding AMP8 equity commitments from the group's parent company, Sandstone Bidco Ltd (SBL), via funds managed by Macquarie Asset Management (MAM) and up to a further £545 million intended to be raised, with at least £245 million of this expected to be committed by 31 December 2025.

The funds managed by MAM have now committed a further £245 million of equity, taking the equity committed by the shareholder since July 2025 to £900 million, and the total invested since its entry in 2021 to £2.55 billion. Over that period, no dividend has been paid -- and none will be paid before 2030.

The £900 million equity commitment is unconditional and is expected to be fully drawn by 30 June 2026.

Of the initial £900 million, Southern Water drew £505 million in November 2025 and expects to draw the remaining £150 million by 31 March 2026. For the second AMP8 Equity Commitment, Southern Water expects to draw the entire £245 million between 31 March 2026 and 30 June 2026.

Funds managed by MAM have also reconfirmed their intention to provide up to a further £300 million of binding equity commitments by June 2026. Southern Water’s anticipated draw down of these funds is expected to be on or around 31 March 2027.

Announcing the funding, Southern Water said the latest equity commitment underscores the continued belief in the strength of Southern Water's case for its AMP8 regulatory appeal to the Competition & Markets Authority, as well as in the UK Government's stated intention to implement reforms to improve the investability of the water sector in England and Wales. As such, the Second AMP8 Equity Commitment - which has been provided on the terms of an equity commitment is not subject to any conditions.

Southern Water CEO, Lawrence Gosden, said:

"We are pleased to have confirmation of £245 million of incremental equity support from funds managed by Macquarie Asset Management.

"This support is vital for us to meet the needs of our customers, the environment and meet new legislative requirements. It enables our largest ever investment programme, including more than £6 billion of growth investment in the 2025-30 AMP8 period, to reduce overflows, meet new environmental standards on river quality, re-build aging water plants and provide additional capacity and resilience."

The incremental £245 million equity commitment takes shareholders’ total investment in the Southern Water group since 2021 to over £2.5 billion.