Westmill Solar Co-operative is the industrial and provident society that owns the Westmill Solar Park in Oxfordshire, England, believed to be the largest community-owned photovoltaic power station in the world.

The project was originally conceived by Adam Twine, the pioneer behind the neighbouring Westmill Wind Farm Co-operative, built in 2011 and registered for the UK feed-in tariffs. It has a capacity of 5 MW_P.

Westmill Solar Co-operative acquired the solar park in October 2012, under an option agreement with the original developers. It raised the necessary finance through public and private share offers and a senior debt bond with a pension fund.

Westmill solar park is in the United Kingdom located on a site of 30 acres near to Watchfield, on the Wiltshire/Oxfordshire border, just off the A420. The site adjoins that of the Westmill Wind Farm Co-operative.

The solar power plant has over 21,000 solar panels^[1] and has been operational since July 2011.

When acquired by the Co-operative, it was the largest community-owned photovoltaic power station in the world.^[2]

The Co-operative invited members through a public share offer, launched in June 2012. Despite the tight timetable caused by the expiry date on the option,^[3] the issue was 50% over-subscribed,^[4] when it closed at the end of July. This raised £4m from c. 1,650 members.^[5]

An additional c. £2m was raised by a private placement of B-Shares, mainly from members who had subscribed to the original issue.

The Co-operative raised the balance of funding required in the form of a 23½-year senior debt bond. This was arranged with the Lancashire County Council Pension Fund,^[6] in what was believed to be the first major funding by a local authority in community-owned energy infrastructure.^[7]

• Community solar
• Westmill Wind Farm Co-operative
• Westmill Woodland Burial Ground
• List of energy cooperatives