＇Maxwell＇s demon＇, in 1871, introduced in science the possibility of using information to generate free energy, Since that time researchers have been speculating about the implications of information for energy use, Recent studies indicate the substitutability between energy and information in the so-called information economies. These studies suggest that information in general and information technologies in particular have the potential to save energy, In this paper an input-output approach is employed to search for empirical evidence of substitutability between energy and information at a national economic level, The development of information activities in the United States economy is studied from 1963 to 1987 and the contribution of information to save energy is indicated, Results show an increasing presence of information activities in all segments of the economy and strong evidence of their contribution to energy savings.