Looking to simulate a small home with different water storage capacities to store energy from active solar thermal collectors. I would like the ability to supply low temperature water to a radiant floor heating system and when storage temperatures drop, then use the water to supply a water source heat pump as back up heat. I would like to know if there are spreadsheet tools designed for this or software that would be relatively user friendly such as Energy-10, if anyone remembers that software that Doug Balcomb helped to develop.