Semi-transparent solar systems are often presented as innovative and aesthetically appealing solutions. However, scientists from Spain warn that they are economically viable only up to a certain level of transparency. Levels above 50% have significantly lower system efficiency per unit area, resulting in higher electricity generation costs.
Researchers from the University of Jaén in Spain conducted a technical and economic analysis to assess the cost competitiveness of semi-transparent photovoltaic technologies (STPV). The study titled ‘Assessment of cost-competitiveness of semi-transparent photovoltaic systems’ and published in the journal Renewable Energy, shows that the costs are closely linked to the level of transparency.
“The paper introduces a cost framework that explicitly links transparency to module cost, structural cost, and system capex, using reference values from real utility-scale PV projects in Spain rather than idealized assumptions. The results explain why many STPV concepts look attractive on paper but struggle commercially, and where targeted policy instruments can realistically help without creating false expectations,” said the study’s lead author João Gabriel Bessa, in a statement to pv magazine.
The researchers analyzed a 1 MW semi-transparent ground-mounted solar system in Spain. The analysis examined total system costs, changes in module efficiency at different transparency levels, as well as the impact of increasing required surface area on the cost per watt and the levelized cost of electricity (LCOE).
Semi-transparent photovoltaic systems are commercially viable only with transparency of up to around 50%
LCOE represents the average cost of producing one unit of electricity over the entire lifetime of a power plant. It accounts for all project costs, from construction and financing to operation and maintenance, relative to total electricity generation, and is used as a key indicator for comparing the cost-effectiveness of different power generation technologies.
The researchers found that STPV remains commercially viable only up to transparency levels of about 50%. As transparency increases, the active solar cell area decreases, leading to lower electricity generation without a proportional reduction in the costs of non-cell materials.
The study’s authors also point out that balance-of-system (BOS) costs—which include all equipment, works, and infrastructure required for a photovoltaic plant to operate, excluding the solar modules themselves—increase with higher transparency levels. This is because the costs of mounting structures and direct current (DC) cabling scale with the physical area of the photovoltaic generators. By contrast, the costs of inverters, alternating current (AC) cabling, transformers, and other electrical equipment are largely independent of transparency levels.
Higher transparency, higher costs
To determine which financial and technical parameters have the greatest impact on LCOE, the researchers also conducted a sensitivity analysis.
Both analyses confirmed that total system costs rise as transparency increases. According to the study, a fully opaque system with zero transparency would have an installation cost of EUR 0.628 per W. As transparency increases, however, module efficiency declines, requiring a much larger area covered by photovoltaic modules to reach the same installed capacity.
At 50% transparency, module efficiency drops to around 10%, doubling the required surface area and increasing total system costs to EUR 0.904 per W. When transparency reaches 90%, efficiency falls to just 2%, requiring a fivefold increase in surface area and raising system costs to EUR 3.110 per W.
Bessa notes that with transparency above a band of 45% to 50%, LCOE rises sharply and exceeds typical market electricity prices, even in regions with high levels of solar irradiation, such as southern Spain.
“As transparency increases, power density declines faster than module costs, because non-cell components such as glass, encapsulation, framing, and logistics dominate the cost structure. This leads to a strong increase in EUR/W module costs, even when less silicon is used,” Bessa said.
The sensitivity analysis also showed that annual specific yield, expressed in kilowatt-hours per kilowatt of installed capacity, is the single most influential parameter affecting LCOE, outweighing even capital expenditure and financing conditions.