Thermal storage is an integral part of most hydronic systems that have renewable energy heat sources. Systems with solar thermal collectors or biomass boilers are prime examples. Systems using water-to-water geothermal heat pumps, or air-to-water heat pumps, are also possible applications for thermal storage, especially when off-peak electrical rates are available. Other possibilities include systems that require heat dumps to shed excess electrical output from photovoltaic arrays, wind turbines or micro hydroelectric turbines.
Thermal storage is also used in small-scale combined heat and power (CHP) systems, or to help meet peak demands in systems where a central heating plant serves multiple apartments that are individually heat metered.