Innovations in the field of information systems (IS) open up new possibilities to increase energy efficiency and carbon reduction. For this, real estate is an industry sector with remarkably high potential. Here IS are integrated into 'Intelligent Houses'. But many of these ecologically advantageous investments are not made yet, because they do not seem to be economically profitable. We therefore develop an IS-specific model to identify investment alternatives out of all ecologically advantageous investment alternatives which are also economically profitable. For this, we compare the investment amount with the achievable energy cost reduction and the raise of the buildings' resale returns. Out of all identified investments we determine the economically optimal investment amount. In this connection we put special emphasis on the valuation of risk and for the first time point out the applicability of Intelligent Houses as insurance against energy price volatility. Thus the quantity of all ecologically advantageous and economically profitable investments is enhanced as well as the economically optimal investment amount. IS' potentials to combine economy and ecology can thus be detected and made useable. An example illustrates how the model can be applied