This paper represents an analytical economic cost model for cloud computing aiming at comprising all kinds of cost of a commercial environment. To extend conventional stateof-the-art models considering only fixed cost, we developed a concise, but comprehensive analytical model which does not only include fixed cost, but also variable cost allowing for the development and evaluation of business strategies for cloud environments. These strategies can be used for both, cloud providers and cloud consumers. The major goal of our model is to comprise all important economic fundamentals and methods. Thus, this new model supports the decision-making process to be applied with business cases and enables cloud consumers and cloud providers to determine their own business strategies and to analyze the respective impact on their business. Based on this model, the energy efficiency of cloud systems can also be evaluated according to chosen business models.