The cash-spinning Nethermills Hydro Scheme, on the banks of the River Ayr, was officially unveiled to the public on Monday.
A ribbon cutting ceremony took place then invited guests were given a guided tour of the project.
The £1m scheme is the fulfilment of a long-held ambition of non-profit firm, Auchincruive-based Energy Agency Renewables.
A single four-bladed Archimedes screw, measuring four meters in diameter, will generate energy from the fast-flowing river.
And the scheme will supply up to 83kW of green electricity to neighbouring Ayrshire College- with any not used being sent to the electricity grid.
Michael Matheson MSP, Cabinet Secretary for Net Zero, Energy and Transport said: “I am delighted to see the Nethermills hydro project on the River Ayr’s historic old mill weir site reaching completion.
"It is great to see renewables projects such as this, not only generating green energy for local use but really focused on maximising benefit to the wider Ayrshire community."
The proceeds will be used to fund projects which reduce fuel poverty in the local area.
Liz Marquis, director of Energy Agency Renewables said: “It gives me great pleasure to announce the opening of this important new hydro scheme which will generate green electricity now and well into the future.
"It will also generate essential funding to the local area to assist our ongoing work in tackling fuel poverty.
"The success in building this scheme has only been possible due to the efforts of our contractors and many partners and I extend my thanks to them for their hard work and dedication.”
Ayrshire College Principal Carol Turnbull said, “We are delighted to be participating in this exciting green energy project which forms part of our College Sustainability Plan."
Since the corn mill at Nethermills was demolished in the 1950s, at least 20 Gigawatt hours of usable energy have passed over the weirs in the centre of Ayr.
The project dates back to 2015, when Energy Agency commissioned a hydrological study, followed by a feasibility and design study by Mann Power Hydro Ltd.
Now the result is a project providing 100 per cent green electricity.
Wildlife enthusiast Hazel Meakin, who was involved in the project from the start of the construction phase, was given the honour of cutting the ribbon.
The scheme will also prevent the emission of an estimated 147 tonnes of CO2-equivalent greenhouse gas annually and continue to generate green energy for many decades- just as the watermills did from the 13th to 20th centuries.
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