A buffer tank is a pressurized thermal storage vessel that stabilizes and optimizes hydronic heating and cooling systems by providing additional water volume to reduce short cycling, smooth temperature swings, and improve overall system efficiency. Commonly offered in a variety of capacities and materials (stainless or carbon steel) with options for internal heat exchangers, high-density insulation, and multiple inlet/outlet configurations, buffer tanks integrate easily with boilers, heat pumps, solar thermal arrays, and CHP systems. By preserving stored energy for peak demand periods and minimizing on/off cycling, a properly sized buffer tank extends equipment life, lowers operating costs, and simplifies control strategies while maintaining compact installation footprints and straightforward maintenance access.