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Glossary · Energy industry & energy transition

Floating PV

floating PV photovoltaics solar energy water surface renewable energies land use

Floating PV (floating photovoltaics, FPV for short) refers to solar systems whose modules are mounted on floating support structures. The system generates electricity like an ordinary photovoltaic system. Its location, however, is not a roof, open land or a façade, but a water surface. In practice these are mostly artificial or heavily human-modified bodies of water such as gravel pit lakes, gravel pits, former opencast mining lakes, storage reservoirs, harbour basins or industrial water surfaces. In Germany, natural bodies of water are legally excluded for solar installations. They therefore do not merely impose higher requirements.

Design and technology

A floating PV system consists of solar modules, floats, connecting walkways, moorings, cables, inverters and a grid connection. The floats hold the modules in a fixed position and tilt on the water. The mooring on the bed or on the shore must withstand wind, waves, fluctuating water levels, currents and, in cold winters, ice. Electrically, the system differs little from other photovoltaics. Capacity is stated in kilowatt peak or megawatt peak, and the energy generated in kilowatt hours or megawatt hours (see Kilowatt, Megawatt and Gigawatt). The real engineering task lies in mounting on a moving base: it must be durable, safe and maintainable.

Floating PV is therefore not a separate energy source and not a fundamentally different way of generating solar power. The term describes the location and construction method. It thus belongs to the same family as other dual-use concepts, such as agri-PV. Besides the conventional design with modules at a shallow tilt, there are also vertically mounted modules, often active on both sides. They cover less water surface but have a lower power density per area.

Floating PV on inland waters must be distinguished from offshore solar at sea. At sea, salt water, higher waves, stronger corrosion, storms, shipping and significantly more difficult maintenance come into play. Inland sites are also only comparable to a limited extent. A pumped-storage reservoir with a strongly fluctuating water level, a drinking water reservoir and a calm gravel pit lake each place different demands on design and operation.

Legal framework in Germany (as of November 2026)

Since 1 January 2023, Section 36(3) of the Water Resources Act (Wasserhaushaltsgesetz, WHG) has regulated nationwide where solar installations are permitted on bodies of water. The provision applies to all solar installations in and above surface waters, regardless of their size. It contains two prohibitions:

  • No solar installation may be built or operated on surface waters that are neither artificial nor heavily modified. A prohibition therefore applies to natural lakes and rivers.

  • On artificial or heavily modified bodies of water, an installation is not permitted if it covers more than 15 percent of the water surface or is less than 40 metres from the shore. Both values are measured from the mean water level line.

A worked example shows what this means: on a gravel pit lake of 10 hectares, at most 1.5 hectares may be covered with modules. Because a shore distance of 40 metres is also required, on small or narrow bodies of water often considerably less usable area remains. Experts disagree on whether, for vertical systems, only the area actually covered counts or the entire project area. No established case law on this is known. In addition to Section 36 WHG, a water law permit is usually required. Also relevant are building planning law, often with a development plan for a special-purpose area, as well as nature conservation law, ownership and lease issues and the conditions for the grid connection. A technically suitable body of water is therefore not yet a site that can be permitted.

The limit values are politically contested. On 26 September 2025, the Bundesrat adopted a resolution on the motion of North Rhine-Westphalia. In it, it asks the Federal Government to extend the limit values in Section 36(3) No. 2 WHG and to enable flexible deviations in individual cases. A resolution, however, does not change the law. In the consolidated version reviewed, Section 36(3) WHG continues to apply unchanged in the version of 1 January 2023. Angling and nature conservation associations partly oppose a relaxation.

In funding law, floating PV is expressly anchored in the EEG 2023. Since the Solar Package I of 16 May 2024, installations on artificial or heavily modified bodies of water within the meaning of Section 3 Nos. 4 and 5 WHG qualify as "special solar installations" (Section 37(1) No. 3 lit. f and Section 48 EEG 2023). They must additionally meet the Federal Network Agency's requirements for special solar installations. Which version applies in an individual case depends on the date of commissioning or of the bid.

Benefits: area, cooling, self-consumption

The most important advantage is the additional area. In densely populated regions, solar parks compete with agriculture, settlements, nature conservation and transport routes. Water surfaces that have already been created artificially, for example at gravel works or opencast mines, can offer further sites here. They are often close to operating areas, power lines and large consumers. Another effect is cooling: photovoltaic modules lose efficiency as cell temperature rises, and the water can cool them somewhat. How strong this effect is depends on rear ventilation, design, wind and climate. A higher yield alone therefore rarely justifies a project.

Economically, floating PV is usually more expensive than a simple ground-mounted system. Floats, moorings, corrosion-resistant components, access via the water and more complex planning add cost. On the other hand, there may be lower land costs, existing infrastructure, a favourable grid connection and above all high self-consumption. This applies, for example, to gravel works, waterworks or industrial operations directly on the water. There, the value of the electricity depends not only on the market price but also on how much purchased electricity is avoided.

Ecological effects

A water surface is not an empty technical plane. The modules shade the water and change light, temperature stratification, wind-driven mixing, gas exchange and evaporation. In dry regions, less evaporation can be an advantage. In nutrient-rich waters, fewer algal blooms may occur. At the same time, the oxygen balance may change, and habitats for aquatic plants, fish and birds may be impaired. The 15 percent and 40 metre rules are expressly based on this precautionary principle, because the effects have so far been little researched. Ongoing research projects examine the effects on species, habitats and water quality in order to derive requirements for site selection and design. For planning and assessment, the following count: coverage ratio, water depth, condition of the water body, materials, monitoring and a decommissioning concept for floats and moorings.

Role in the power system

Floating PV has the same generation pattern as other photovoltaics: a lot of electricity when the sun shines, none at night, more in summer. It increases the quantity of renewable electricity but provides only little firm capacity. For dealing with residual load, the same questions therefore arise as with other solar installations. A system is most useful when combined with storage, controllable consumers or existing hydropower and pumped-storage infrastructure.

Common misconceptions

  • "Floating PV solves the land question": The conflict over land merely shifts to bodies of water. There, the issues are water protection, fishing, recreational use, landscape appearance, and drinking water and flood protection.

  • "Any lake is suitable": In Germany, only artificial or heavily modified bodies of water come into question. Even there, only a small part of the area is usable.

  • "Floating PV is automatically nature-friendly": Whether a system is nature-friendly depends on the site, the coverage, the condition of the water body and the monitoring, not on the label.

  • "Operation is simple": Access, cleaning, replacement of components and fault clearance must be possible in changing weather and water levels. What looks calm on the site plan is a moving location in operation.

Floating PV is thus not a blanket solution for solar expansion. It is a siting option with narrow legal and ecological limits. It makes sense where the type of water body, technical design, ecological compatibility and integration into the energy system fit together.

Sources

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Edited by eCMS on 12.11.2026 05:05

© 2026 Erik Schmidt. All rights reserved. Quotations with a link to the source are welcome.