Hydronic buffer tank acts as a thermal storage reservoir, holding a volume of heated water so that excess thermal energy generated by a heat source — such as a heat pump, boiler, or solar collector — can be stored and released as needed. By increasing the water volume in the system, a buffer tank prevents frequent cycling of the heat source, which can reduce wear, extend equipment life, and improve overall energy efficiency. Buffer tanks also help maintain a more consistent temperature and even out fluctuations in demand, ensuring steady heat delivery to radiators, underfloor heating, or other distribution systems. They are especially useful in systems with variable load conditions or intermittent heat generation, enabling smoother operation and lower operating costs. Buffer tanks do not typically contain internal heat exchangers; instead, they provide the necessary thermal mass to balance supply and demand in hydronic systems.