Have you heard the one about the reservoir in LA that was covered in 96 million black plastic balls? True story. Each ball cost 36 cents, costing the city $300 million. A delighted Mayor Eric Garcetti — who released them at a photocall in August 2015 with the cry of "balls away!" — told the news channel KABC, "By reducing evaporation, these shade balls will conserve 300 million gallons of water each year, instead of just evaporating into the sky." The balls would last 10 years, before being recycled and replenished.

In fact, they were removed in under two years, in March 2017. During that time, they did prevent around 1.7 million cubic metres from evaporating (450 million gallons — so Garcetti was right). However research found that the oil, natural gas and electricity used in the manufacture of the plastic balls would have used around 2.9 million cubic metres of water, far more than was locally saved. And much more has since been discovered about the breakdown of plastics in water causing microplastic pollution. It was rightfully dubbed "a failed experiment".

However, around the same time, other world regions were experimenting with something much more sensible: covering water surfaces with solar panels.

Small-scale sites had begun in the 2000s. But the first large-scale floating solar plant was developed in Japan in 2016: a 13.4 megawatt (MW) installation on the reservoir above Yamakura Dam, Chiba Prefecture, using 50,000 solar panels (see pic below). But then China got in on the act, and the scale snowballed. The Huainan plant opened in 2017 — the same year that Mayor Garcetti reluctantly closed his ballpit — spanning over 800,000 square meters and producing up to 40 MW of electricity, enough to power an entire town. With pleasing symbolism for the energy transition, the plant floats on a flooded former coal-mine.

Floating solar panels have rapidly become the ultimate win-win, reducing evaporation loss and producing renewable energy at the same time without taking up land. If just 6% of Lake Mead were covered in solar panels, it would produce more electricity than the Hoover Dam itself. If just 1% of Africa's megadams were fitted with floating solar, it would be double Africa's hydropower capacity. The panels are also more efficient thanks to the cooling effect of the water, adding an energy gain of 5% to 15%.

Algal blooms — an increasing problem in lakes around the world, which can significantly decrease water quality and cause health issues — are reduced by floating solar, too. The installations can prevent algal blooms from taking over a lake by shading an area of the water, slowing the growth of algae.

Global installed capacity for floating solar first passed 1 Gigawatt (GW) in 2018 and reached 7.7 GW by 2023. Almost 90% of the installed FPV capacity was in Asia, with over 50% of in China alone.

A World Bank document states that, "At some large hydropower plants, covering just 3–4 percent of the reservoir area with FPV [floating photovoltaics] could double the estimated installed capacity, potentially allowing water resources to be more strategically managed". While in terms of water loss, a case study of Lake Nasser, Egypt, a region that suffers from extreme water scarcity, found that 50% coverage would result in 9 billion m3 of water saved from evaporation annually.

On December 27, 2023, China's largest floating PV power project connected to the grid in Fuyang, Anhui Province. Built by CTG, the project boasts a total installed capacity of 650 MW, with 1.2 million solar modules. Its 700 GWh of electricity annually is calculated to replace 220,000 tonnes of coal and reduce carbon emissions by nearly 580,000 tonnes per year. It again uses a former coal mining site, and combines solar power generation with aquaculture — farming fish beneath the panels.

It's not the only aquaculture-fishery hybrid. The 550 MW, Wenzhou Taihan floats above tidal fishing water. Connected to the grid in December 2021, it has 1.396 million solar panels of 450W each (the same capacity, incidentally, as my own rooftop panels. But I've only got 12 of them).

Can the rest of the world follow?

The world is now looking to China's floating solar and wondering, can we do the same?

In 2024, researchers from Lancaster and Bangor Universities and the UK Centre for Ecology & Hydrology, aimed to calculate the global potential for floating photovoltaics or 'FPV'. (The media term 'floatovoltaics' has so far failed to float.) The research published in Nature Water found that the daily electrical output for floating solar could supply all — yes all — the electricity needs of some entire countries. And this was only including water surfaces that met a strict criteria: no more than 10km from a population centre, not in a protected nature area, didn't dry up or freeze for extended periods, and with FPV only covering a maximum 10% of surface area (any more was deemed potentially harmful to freshwater habitats).

Many countries — mainly from Africa, the Caribbean, South America and Central Asia — were found to have the potential for 40% to 70% of their annual electricity demand met through FPV alone. Even in Northern Europe, it could provide a significant contribution to future energy demand: Finland could meet 17% of its electricity demand from FPV and Denmark. The UK could produce 2.7 TWh of electricity each year from FPV, enough electricity for around one million homes. In total, nearly 68,000 lakes and reservoirs worldwide were found to be FPV suitable.

Floating solar also comes without the NIMBY resistance of solar farms on agricultural fields, and therefore garners more cross-party support. In the UK, a Conservative MP recently wrote an open letter to the local water company stating: "The technology exists to place solar arrays on reservoir surfaces. Studies show that covering just a fraction of the UK's reservoirs could generate massive amounts of power without touching a single blade of grass. The water cools the panels, making them more efficient than field-based installations. This is the smart, 'dead space' utilisation we should be championing." (Albeit his main point was to oppose solar panels on farm land, which I personally don't mind — someone should introduce him to agrivoltaics).

There are currently very few FPV installations in the UK, with the largest being a 6.3MW floating solar farm on the Queen Elizabeth II reservoir, near London. But Associated British Ports recently announced plans for a genuinely large-scale 40MW floating solar plant on Cavendish Dock, Barrow-in-Furness, covering around one-third of the dock's water area. Research shows that the UK has the potential for up to 2.7TWh of annual generation from FPV projects.

In mainland Europe, France and The Netherlands are the two leaders in this space. The Bomhofsplas Floating Solar Park in Zwolle, Netherlands, is a 27.4 MW renewable energy project on an 18-hectare sandpit lake built by BayWa r.e. and GroenLeven, powering 7,200 homes. While the French floating solar developer Ciel & Terre has been involved in a number of the Chinese mega-projects, but has since found a domestic market too. In 2025 they installed the 72 MW Les Ilots Blandin plant in a former quarry site in Perthes, France — currently the largest in Europe, though such records are tumbling all the time — plus a 25MW plant at Leutenheim, France.

Floating solar "opens the doors for countries with land constraints to boost their sustainability goals," says Valentina Puccini, a senior energy specialist at the European Investment Bank (who incidentally quit her job in oil and gas to work in renewable energy). "We're starting to see some nice projects around the continent."

India is also beginning to rival China in terms of ambition and scale. The Madhya Pradesh 120 MW plant uses 219,270 floating solar panels (and 550 KW each, making it more efficient than earlier sites). The lake is also far deeper than most. For this project, Ciel & Terre India developed a unique robotic anchoring barge capable of installing anchors to the lake bed depths of 25 to 30m.

Indonesia too, with no shortage of water bodies, is pushing ahead with floating solar. Analysis by the Institute for Essentials Services Reform (IESR) states that the potential for floating solar in Indonesia is up to 28.4 GW, spread across 783 reservoirs and lakes, each with a minimum potential of 1 MW. The Indonesian government is now planning 60 FPV sites, including the 145 MW Cirata plant, one of the largest in South East Asia. The wider region is already home to a number of large-scale floating PV systems including Vietnam's 70 MW FPV system in Quang Thanh which came online in 2021, and Singapore's 60 MW facility at Tengeh reservoir, also in 2021. While in 2025, the Philippines added a 5 MW floating solar plant to the Malubog Reservoir in Toledo City, Cebu (see pic below). And this is by no means an exhaustive list — I'm just picking out the most eye-catching.

Competing technologies

Given the technical and geographical challenges, there are a number of competing engineering designs and firms. While FPV doesn't have the same land costs, the initial instal and ongoing maintence is a little trickier — and costlier. According to a 2025 review of floating solar by the IEA, there is a cost premium of 20–25% compared to ground-based solar PV.

There is also an additional vulnerability to storms — especially hurricanes. The pioneering 13.4 MW installation in Chiba, Japan, was hit by Typhoon Faxai in late 2019, causing the panels to buckle and pile up at the lake edge — including spectacularly catching fire. Rubber-neckers can watch the clip below:

The site reopened at full capacity, with strengthened fittings, in 2021. But the typhoon damage served a useful lesson for competing engineering firms working in this space. The race is on to perfect floating solar arrays that provide the greatest climate resilience, solar efficiency, and ease of maintance (the most important of which is cleaning of the panels).

In late 2025, Ciel & Terre unveiled a new floating solar technology, Fusio, designed to boost performance, scalability, and operational efficiency in large-scale FPV projects. According to its website, this triangular honeycomb design (see pic below) draws on structural engineering principles used in bridges and skyscrapers to ensure stability and load distribution. The system's "low float footprint and elevated PV configuration" aims to increase airflow under the modules, enhancing cooling and potentially raising energy output by a further 2%. According to Ciel & Terre, maintenance has been redesigned through a catamaran-based system with access to all PV panels, inverters, and cabling.

An intriguing vertical design was recently unveiled on a gravel pit in Germany in late 2025. With an installed capacity of 1.87 MW and an expected annual output of around 2 GWh, the vertical panels cover just 4.65% of the lake's surface area. The patented SKipp system developed by SINN Power introduces a keel-like substructure extending up to 1.6 meters below the surface, which secures the modules and allows controlled movement under changing winds and water levels. A second 1.7 MW phase is already planned, still keeping well below the 15% maximum lake coverage allowed under German law.

On the Itaipu Reservoir, Paragauy, installed by engineering consultancy OWC, the access to panels is provided by floating walkways in-between the solar panels (see pic below). This allows manual cleaning of the panels in much the same way as for ground-based PV. The floating walkways lose some of the potential square meterage for the PV itself, but also provide extra strength and stability for the entire array.

The 41MW Hapcheon Dam Floating Solar Project in South Korea is another contrasting take, featuring over 92,000 solar panels arranged in 17 flower-shaped, floating structures, operational since late 2021.

Such is the increasing robustness of modern FPV that some are even being trailed offshore — ie. out at sea. A collaboration between Dutch-Norwegian company SolarDuck and German energy company RWE has built a floating solar platform on the North Sea, approximately 12 kilometers off the coast of Scheveningen. It looks something like an oil rig platform — see pics below. Dubbed the 'Merganser', it only has a capacity of 0.5MW, so is just at the pilot stage — but the companies involved claim that it has already been proven to withstand extreme offshore conditions, and can be scaled in future by simply interconnecting more platforms.

China's first commercial ocean FPV project came online in 2025, off the coast of Qingdao, Shandong Province. It allows the PV panels to synchronise with tidal elevations, reducing the distance between the panels and the water surface to about one-tenth of traditional pile-based structures. This design aims to optimise seawater cooling, with specially engineered salt-resistant floats and supports (also designed to prvenet barnacle growth) and an underwater anchoring system designed to withstand wind speeds up to level 13 (133–148 km/h). When complete, Qingdao will reach 23 MW capacity.

Ocean Sun has also developed a floating rig of flexible solar panels which move with the waves as they pass underneath (see image below). "It has the effect that it dampens the waves, and it prevents the breaking of the waves," chief executive Borge Bjorneklett, told the BBC. He claims the system has survived category four typhoons during a test in a reservoir. The BBC also raises the prospect that offshore FPV could even be sited far out at sea where they could serve as refuelling points for electric ships.

Perhaps incredibly, Sinn Power plans to bring its German vertical floating solar concept to the open ocean, too. With its under-water keel and vertical panels looking (and acting?) somewhat like a sail-ship, the prospect is certainly intriguing.

What's next?

China has since brought the world's first 1 GW FPV plant online — connected to the grid in December 2025. Not just that, but the site in Dongying, Shandong province, is also ocean-based.

The Dongying site (given the rather unsexy name 'HG14') occupies 1,223 hectares of shallow coastal waters, 8 km from shore, with depths of 1 meters to 4 meters. It is made up of nearly 3,000 photovoltaic platforms, each platform measuring around 60 metres in length and 35 metres in width (roughly the size of three basketball courts), anchored by a total of 11,736 steel piles. Zhang Bo, deputy manager of the project, is quoted as saying: "The project uses a 'four-pile foundation plus solar platform' structure, with the panels tilted at a precisely calculated 15 degrees. This enables the installation to withstand force 11 gales and winter sea ice, while reducing steel consumption by more than 10 percent."

A single photo doesn't do justice to the scale of the Dongying plant — so check out the video below for the drone footage.

China is also instrumental in bringing mega-floating solar to Africa. A floating solar facility in Zimbabwe is to be developed at the Kariba Dam in 2026 which would deploy around 1.8 million solar panels. Government officials have said the project will be implemented in three phases over a five-year period. Anxious Masuka, Zimbabwe's Minister of Lands, Agriculture, Fisheries, Water and Rural Development, told the press that the project will have a "minimal footprint" covering 10 km2, or around 1% of the total surface area.

Meanwhile, in California the local authorities have long since given up on black plastic balls. In December 2025, the City of Petaluma completed the Ellis Creek Floating Solar Project — the largest floating solar installation in California to-date. The floating solar array on a 17-acre treatment pond at the Ellis Creek Water Recycling Facility (ECWRF) allows the City to generate clean, reliable electricity without using additional land. There's a pretty cool video on LinkedIn of it being installed:

By producing 98% of the facility's electricity on-site, the floating solar system will significantly reduce Petaluma's reliance on grid power, cutting greenhouse gas emissions and advancing the City's goal of achieving Carbon Neutrality by 2030. It is saving the City $500,000 on average per year. "This will help reduce water rates for the whole community", said Mayor Kevin McDonnell. "This is cost-savings powered by innovation — and a model for how cities can lead the way in climate action." Now that sounds an awful lot better than "balls away!" We've come a long way in just ten years.