In the study of solar water heating in central Montana, a system was built to use the sun during the course of a January day to heat the water in a 150-liter domestic hot-water tank to 66 degree C. Given an input water temperature of 4 degree C, the area of solar collectors required was 6. 8 m**2. Collectors of 7. 4 m**2 were used. Three separate collector systems with different components were to be set up to provide direct comparisons, two made of aluminum and one of copper.