Thermal mass systems can store solar energy in the form of <answer>heat</answer> at domestically useful temperatures for daily or interseasonal durations. Thermal storage systems generally use readily available materials with high specific <answer>heat</answer> 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 <answer>heat</answer>ing and cooling requirements.
In what form do thermal mass systems store solar energy?
heat