The aim of this paper is to assess the implications of an ongoing improvement in the energy efficiency of the Polish economy. Poland is among countries that have been leading the way in reducing energy intensity in recent decades. A counterfactual analysis conducted in this study is based on a computable general equilibrium (CGE) model called GEMPOL and captures six dimensions: the overall economic activity level; the industry pattern of output; the product pattern of foreign trade; energy-related expenditures; the quantity of energy used; and the revenue and expenditure of the public finance sector. An accompanying sensitivity analysis underlines the positive relationship between the expected economic effects of improved energy efficiency and the assumed scale of such technological progress, as well as the positive relationship between the magnitude of those consequences and the assumed substitution elasticity values. The obtained results can constitute an important contribution to a scholarly debate on the long-term impacts of decreasing per-unit energy use on the characteristics of Poland’s economy and resulting policy challenges.