Floating Solar PV Engineering: Mooring and Design

Last updated: November 2026

Floating solar (floating PV, or FPV) is a solar plant built on floats on a lake, reservoir or pond. You design it like a ground plant in some ways and like a boat in others. This guide gives the main design steps and the numbers we could trace to a source. Where no source gave a number, we say so and leave the number out.

Most numbers below come from Where Sun Meets Water: Floating Solar Handbook for Practitioners (World Bank, ESMAP and SERIS, 2019). It is a few years old, so check newer standards and float data for your project.

Floating solar design at a glance

How do you choose a water body for floating solar?

Pick a fresh, man-made water body with a single owner, and avoid sites with high winds. The handbook says FPV is best placed where the water is 15 meters deep or less, with little change in level. It lists man-made reservoirs, hydropower dams, industrial ponds, mine subsidence areas and irrigation ponds as high-preference sites. It lists natural lakes and tourist sites as low preference.

Look at these points before any layout work:

• Area. About 1 MWp needs roughly 1 hectare of island and 1.7 hectares of water after anchoring.
• Shape. A square or rectangular water body wastes less area. Islands or obstacles in the water cut the usable area.
• Water level. Collect depth at many points and the level changes through the year. If the level changes a lot, design for the extremes.
• Wind and waves. Study the wind direction, gusts, waves, currents and the fetch (the open water length the wind blows across).
• Bed. The handbook lists hard ground for anchoring as high preference and soft mud as low preference.
• Water. Fresh water with low salt is preferred. Salty or dirty water raises corrosion risk.

For bathymetry (a map of the water bed), the handbook says grid sizes range from 100 m by 100 m to 2 m by 2 m. It calls 5 m by 5 m a reasonable choice. Do a coarse survey first, then a finer one on the best area.

For rules at the sites you may use, DNV’s recommended practice DNV-RP-0584 (edition 2026-09) focuses on sheltered inland water. It also applies near shore, with significant wave heights up to 2 to 3 m. You need a subscription to read the full text, so we do not quote its values.

What tilt should floating solar use?

Use a low tilt. The handbook says most FPV plants use tilt angles not greater than 15 degrees. The float design and the wind load limit the tilt. Some floats allow 5 to 20 degrees.

A low tilt has two other effects:

• Rows shade each other very little, so rows can sit close together. Row spacing is set by the float design.
• The handbook recommends at least 10 degrees for self-cleaning by rain. It puts normal soiling at 1 to 3 percent, but bird droppings can push it much higher.

Bifacial modules (they also take light on the back) may not help. The handbook reports that water reflects an average of only 6 percent of light at typical daytime angles. It says bifacial modules on FPV will likely not gain power from that reflection.

Does floating solar make more power than ground solar?

Often yes, but the size of the gain depends on climate. The handbook says floating PV shows an overall higher initial performance ratio, by 5 to 10 percent, depending on the climate (table 3.1). Air over water is cooler and windier, so modules run cooler.

In the Singapore test site, air above the water was about 1 to 3 degrees Celsius cooler than over an adjacent rooftop. The handbook estimates that raising the heat-loss coefficient (U-value) from 30 to 35 W/m2K would add about 1 percent to yield there, or 16 kWh/kWp. The cooling is best for free-standing floats with open space behind the modules. It is weaker for large, tightly covered platforms.

The handbook also warns that standard weather data and software do not show this cooling by default. You may need to adjust the module temperature model after a site survey. Model it by the hour, not with a flat percentage.

How do floats and islands work?

A floating island carries the modules, the electrical equipment and the people who build and maintain it. Floats are generally HDPE (high-density polyethylene), with additives for UV resistance. Metal frames or other mounts hold the modules at the chosen tilt.

Wind load limits the size of an island. The handbook says these stresses are usually checked with finite element analysis (FEA) and computational fluid dynamics (CFD). Leave walkways or space for crews to move. Floats should last as long as the plant, since modules are rated for 20 to 25 years.

The handbook lists tests to ask your float supplier for:

• wind-tunnel test on an assembled platform
• tensile strength and bending fatigue tests
• UV and temperature ageing test for the design life (25 years)
• fire resistance and corrosion tests
• buoyancy and puncture test
• drinking-water compatibility test, if the water supplies drinking water

How do you moor and anchor a floating array?

Moor the array so that no single failure can spread. The handbook says the system should have redundancy, so that failure of one line does not cause a chain of failures. The right design depends on the site, so have a qualified marine professional approve it.

The handbook says simple shore anchoring is typical in smaller water bodies or very deep ones. It says complex anchors suit reservoirs with great water level changes. It gives no depth limits for each anchor type, so ask your supplier and marine engineer.

Mooring lines can be wire rope, galvanized steel wire, chain, synthetic rope, elastic rubber hawsers, or a mix. Buoys or extra weights can keep lines taut and absorb level changes. Lines should be as horizontal as possible, because line tension equals wind force divided by the cosine of the line angle.

Wind load calculations are mandatory for the mooring. The handbook points to European code EN 1991-1-4 for wind actions on structures. It also says marine standards such as DNVGL-OS-E301 (position mooring) can be a reference.

What goes wrong in strong wind?

The handbook reports that two large Japanese FPV systems were damaged by typhoons, in 2016 and 2019. The 2019 event led to a fire. A tornado in the Netherlands in 2019 flipped a few arrays. The handbook lists common causes for flipped edge rows:

• Anchor points were not at the edge floats.
• Edge floats carried modules, so they caught uplift.
• Water was low, so loose lines could not absorb wind load.
• Waves were higher than expected.
• Mooring points broke when slack lines suddenly went tight.

It lists fixes: stronger float connection pins, a better mooring design, empty floats along the edge, weighted edge floats, and windshields behind the edge panels.

How do you handle cables and electrical safety?

Plan cable slack with care. The handbook says slack must cover both island movement and water level changes. If it does not, tension can snap the cables. Cables can float in watertight conduits or run as submarine cables, which cost much more. Plan them so they do not block boats.

On the electrical side:

• Inverters can sit on the islands, or on shore for small systems near the bank. Long DC runs to shore raise voltage and ohmic losses.
• Inverters on the water need extra safety measures against sinking and tipping.
• Ground exposed metal parts. The handbook gives copper bonding cables of at least 6 mm2, up to 16 mm2 depending on the cable length.
• Specify junction boxes rated to a minimum of IP67 and avoid submerging them.
• High humidity lowers insulation resistance and raises the risk of electrical leakage.

How do you plan maintenance for floating solar?

Plan for it at the design stage. The handbook says floating panels are in general harder to clean, inspect, repair and replace than ground-mounted ones. A broken module must be moved by boat, and crews work standing on floats.

• Walkways. Without walkways, trained crews need special equipment and boats to reach the panels. This likely adds time and cost. The handbook advises a cost-benefit check of the extra floats for walkways during design.
• Soiling. The handbook calls soiled modules the greatest O&M concern. Floats attract birds, and droppings cause partial shading and hot spots. Droppings also carry seeds that can sprout on floats and cable joints.
• Cleaning. Crews use soft sponges, non-abrasive brushes or cloth. The handbook discourages chemicals, and pressure and steam cleaners. Water from the water body can be used for rinsing, except in corrosive water such as seawater. It gives one typical case: a team of six workers takes four days to clean one MWp.
• Inspection. The handbook lists a monthly visual check for shade and clean surfaces. It lists a quarterly check for cracks, glass fractures, discoloration, delamination, moisture and frame corrosion. It adds a yearly recommissioning and thermal imaging, for example with a drone.
• Crew. Work on water needs life jackets, boats, boat permits where required, and radios. Train the crew.

Does floating solar cost more?

Slightly more, on average, according to the handbook (table 5.1). It names floats, anchoring, mooring and plant design as the reasons. It also names benefits: extra yield from cooling and, depending on the design, less water lost to evaporation. We do not give a percentage or a price per watt, because we found no figure we could trace to a primary source.

The handbook also says permitting is generally harder for natural lakes and easier for artificial ponds. It reports that cumulative floating solar was approaching 1.1 GWp in mid-2018 (World Bank market report, executive summary (2018)). Newer capacity figures exist, but we have not sourced one.

How can SurgePV help?

SurgePV supports energy-yield modeling, financial modeling, shading analysis, layout and proposals. We do not state that it models floats, mooring or water-body loads. Bring a floating project to a demo and ask how tilt, spacing and yield would be set up. For a wider view of design tools, see software for solar systems. For ground plants, see our solar farm design guide.

For related reading, see floating solar farms and clean energy and floating solar design basics. For the shading step, see shading analysis. To see how yield and financial modeling would be set up for your site, book a demo.

Frequently Asked Questions

What is floating solar?

Floating solar, or floating PV (FPV), is a solar plant built on floats on a body of water such as a reservoir, pond or lake. The floats are usually made of HDPE plastic. Anchors and mooring lines hold the plant in place.

What tilt do floating solar arrays use?

The World Bank and SERIS handbook says most FPV plants use a tilt of 15 degrees or less. Some floats allow 5 to 20 degrees. Float design and wind load limit the tilt.

How deep should the water be for floating solar?

The handbook says FPV is best placed where the water is 15 meters deep or less, with little change in level. It gives no minimum depth. Water level changes must be designed for. If the water body can dry out, it is a low-preference site.

How much water area does floating solar need?

The handbook says about 1 MWp needs roughly 1 hectare for the floating island and 1.7 hectares of water area once anchoring is counted.

Does floating solar cost more than ground-mounted solar?

Slightly more on average, according to the handbook, because of floats, anchoring, mooring and plant design. It names extra yield from cooling and lower water evaporation as possible benefits. We found no cost figure we could trace to a primary source, so we give none.

What water bodies are best for floating solar?

The handbook lists man-made reservoirs, hydropower dams, industrial ponds, mine subsidence areas and irrigation ponds as high-preference sites. It lists natural lakes and tourist or recreational sites as low preference. Fresh water with a single owner is preferred. Sites with high winds are low preference.

How do you maintain floating solar panels?

Plan walkways at the design stage, clean with soft tools and water from the water body, and inspect monthly and quarterly. The handbook says soiling from bird droppings is the greatest concern, and that floating panels are harder to clean, inspect and replace than ground-mounted ones.