Thermal mass systems can store solar energy in the form of heat at domestically useful temperatures for daily or interseasonal durations. Thermal storage systems generally use readily available materials with high specific heat capacities such as water, earth and stone. Well-designed systems can lower peak demand, shift time-of-use to off-peak hours and reduce overall heating and cooling requirements.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What is something that can be accomplished by a thermal mass system?
reduce overall heating and cooling requirements