Energy demand caused by the use of buildings can be minimized by energy efficient building energy systems. Building automation and control is an essential part of those systems and ensures a demand-oriented energy supply due to automation, control and management of any building energy system. Therefore the effectivity of building automation and control systems and their contribution to energy efficient building perfomance requires quantification when verifying minimum requirements regulated by public law or in the context of investment decisions. Accordingly, this article will describe appropriate calculation methods.