AbstractThe results of measurements on a few solar air and water heaters of the same design, but made from different plastic materials, are reported for different climatic conditions. The experiments on the systems were made over a long time period, first in Germany in 1982 and then in India in 1984. An economic evaluation shows that the use of such collectors can bring down the cost of solar energy in the desired economic scale. Despite the drawback of UV degradation of plastic material resulting in shorter lifetime, the low initial investment cost keeps the cost of useful energy also low.