Vaillant combi boilers are energy efficient, help you cut costs on your energy, and they're also quiet in operation, reliable and take up minimal space. The boilers by brand Vaillant are typically A rated and don't require a separate water tank or cylinder, helping save space and reduce installation disruptions. Some models of Vaillant boilers include advanced technology, such as weather compensation and the ability to adjust the boiler temperature by your smartphone from anywhere, anytime.