Free Sunlight, Paid Subsidies: What a Space Station, a Power Market and a Solar Fence Say About the Cost of Free Energy

Sunlight is free; the equipment that collects it, the grid that carries it and the backup that covers its absence are not. This preprint examines three cases that show where the cost of "free" energy lands. First, the arrays of the International Space Station: about 2,500 m² of silicon producing 84–120 kW for a crew of 3 to 7 in the best light conditions available to any solar panel. Second, the German wholesale power market, where calm and dark weather replaces cheap generation with expensive gas and pushes prices above €300 per MWh. Third, the insolvency filing of two companies that built vertical solar fences on farmland in early October 2026, after a subsidy for agri-photovoltaics was not approved and private capital did not follow. The common thread is that these systems survive on operating support, not on the price of the energy they sell. Public money is well spent on research and development; it is poorly spent when it becomes a permanent condition of the business case.