Active solar heating was a favorite topic after the first energy crisis. Usage for space heating, however,proved to be completely uneconomic. Domestic hot water systems, instead, retained attention. Theycan be used year-around and have a much larger share in the hot water energy bill than space heatingsystems have in the heating bill. Of course, in the past, energy use for domestic hot water wasonly a fraction of the energy needed for space heating. As buildings became much more energy efficient,that fraction slowly increased, to attain a close to 50% share in todays very low energy homesbuilt in countries with a cool climate. That fact could turn solar boilers into an economic efficiency option.To get better knowledge of the avoided energy, two private homes got a fully monitored solarboiler installed. Logging started in January 2005. In the paper, the measured data for one of thehomes are commented. The data gained are also compared with the avoided energy consumption, aspredicted with the energy performance methodology. An economic evaluation is added.