The exponentially growing traffic in cellular networks induced standardization groups to focus on spectral efficiency (SE) and providers to densify their networks in crowded areas. The price to pay is a significant reduction of the energy efficiency (EE). As a result, more balanced EE-SE solutions have attracted significant interest lately in the wireless community. However, the Pareto optimal bound of this problem is so far not well established. This paper makes a step by defining precisely this bound in a typical cell where the interference-plus-noise distribution is known. An analytical EE-SE bound is derived considering an optimal superposition coding mode and also three sub-optimal time-frequency sharing approaches. The typical noise-plus-interference distribution used in this paper is obtained from Poisson distributed cellular network simulations validated by the Greentouch reference model, but the analytical results broadly apply to any other reference distribution.