Thames Water has started the formal procurement process for its major Farmoor Floating Solar PV project – which includes a commitment by the water company to take all energy generated from the installation.

The water company is planning to install a floating solar array at Farmoor Reservoir to help power the water treatment works. The solar array will be located within the north section of the reservoir known as Farmoor 1. It will produce enough renewable electricity to power around a quarter of the site’s needs.

Thames is now working to find a partner who will design, build and operate the project on its behalf – the utility hopes to be in a position to start building in autumn 2026. Construction is expected to last around 16 weeks.

The project includes funding, design, build, ownership, operation and maintenance for the Farmoor Floating Solar PV (FPV) Project for up to 4MW, with a standard Power Purchase Agreement (PPA) in place (£ per kWh).

The total value of this project will be determined by the PPA price as per an agreed bid sheet, over the term of the agreement.

The scope of work under the project covers:

• full design and engineering
• procurement
• full MEICA installation
• commissioning (including commissioning activities at point of connection)
• Distribution Network Operator (DNO) witnessing, testing and approval to satisfy the terms of the connection agreement or offer
• supporting OFGEM accreditation for REGOs
• operation and maintenance, monthly and annual reporting
• training of emergency procedures
• training of essential operational activities
• documentation
• demarcation fencing and signage
• biodiversity net gain requirements and any visual impact requirements.

The PV installation will be floating with a maximum capacity of 4MW – thesuccessful supplier will be required to design and optimise the size of the PV plant for behind-the-meter use and achieve an attractive payback period and NPV. The PV plant will require inhibiting when the board is being fed from the generator or in an island situation.

Thames also specifies that the PV plant must use the most efficient and appropriate components to ensure an efficient and low-maintenance system.

The contract will be awarded to a single supplier via PPA model, with a subsequent Lease Agreement.

Interested providers are being invited to complete a Procurement Specific Questionnaire - the PSQ will have one 'General & technical PSQ' questionnaire which all bidders are required to complete. Responses to the PSQ will be evaluated against selection criteria, to select bidders to proceed to the next stage of the procurement process.

Thames Water will then short list the top scoring 8-10 bidders who will progress to the Invitation to Negotiate (ITN) stage. The selection criteria will be a combination of financial and non-financial factors and will include legal and financial capacity, alongside technical ability to perform the contract. Organization questions include financial and economic standing, Forms of Security, Health and Safety etc., while technical questions will include experience, capability, O&M experience, environment, workforce and subcontractors, innovation and quality assurance.

The PSQ questions will consist of:

1. Pass/Fail Questions

Pass/Fail questions are stated in the Questions - failure to meet the requirements in these questions may result in elimination of the Bidder

2. Weighted Questions

The scores given for weighted questions are used to calculate the final score.

3. For information only

Some questions are for information only; these will not be scored

The PSQ submissions will score and shortlist the bidders who pass the selection criteria to progress to the next stage. Thames will shortlist the top scoring 8-10 bidders, with the top scores, who will progress to the ITN stage.

Responses at the ITN willbe evaluated in accordance with Most Advantageous Tender (MAT) award criteria - both technical and commercial responses will be scored in detail and weighted to give an overall score.

For the three Stage ITN Process, Thames Water reserves the right to shortlist 3-5 bidders through to ITN Stage 2, with their Stage 1 scores being carried over, and their technical score being reapportioned. The highest scoring bidder at ITN stage 2 will then move through to ITN stage 3, to negotiate the final agreement.

Thames Water envisages that the contract will be awarded for an initial term of 15 years with options to extend by 5 years or longer, up to a maximum overall term of 25 years. Award decision date is currently estimated in April 2026. Current estimated start and end contract dates are 24 April 2026 to 23 April 2041 with a possible further extension option to 23 April 2051.

Thames Water Procurement is now inviting interested suppliers to complete a Registration of Interest formto request access of participation in the procurement. At this stage the water company requires a company name and contact details of two people within the organisation with whom Thames can correspond.Once registered suppliers will then have access to the PSQ and related documents necessary to complete their initial submission.

Tender submission deadline is 10:00am on 21 October 2025  - click here to access the online registration form.