The selection of an architectural style for a given software system is an important factor in satisfying its quality requirements. In battery-powered environments, such as mobile and pervasive systems, efficiency with respect to energy consumption has increasingly been recognized as an important quality attribute. In this paper, we present a framework that (1) facilitates early estimation of the energy consumption induced by an architectural style in a distributed software system, and (2) consequently enables an engineer to use energy consumption estimates along with other quality attributes in determining the most appropriate style for a given distributed application. We have applied the framework on five distributed systems styles to date, and have evaluated it for precision and accuracy using a particular middleware platform that supports the implementation of those styles. In a large number of application scenarios, our framework exhibited excellent precision, in that it was consistently able to correctly rank the five styles and estimate the relative differences in their energy consumptions. Moreover, the framework has also proven to be accurate: its estimates were within 7% of the different style implementations? actually measured energy consumptions.