Storage tanks serve to accumulate excess heat from its source. The source may be a solid fuel boiler, heat pump, solar collectors, a fireplace insert etc. Some types of tanks allow combining and connecting multiple sources of heat

NAD and UKV (storage tanks (without DHW preparation) serve only for storing heat in the heating system, NADO (with DHW preparation) tanks also allow direct water heating in the inner enameled vessel or water preheating for another water heater.