Viscous dissipative heating has long been discussed as a heat source in solid celestial bodies experiencing exogenic forces such as tidal forcing or surface loading. We examine the characteristics of viscous dissipative heating in a Newtonian, Maxwell viscoelastic solid in a 2D Cartesian box subjected to a surface load. The solutions are analyzed to understand the general controls on the energetics of planetary mantle that are associated with exogenic forcing. We find that work done at the surface is partitioned between dissipative and elastic terms depending on mantle viscosity, loading period, and loading wavelength. For viscosity structures with a weak upper mantle layer, dissipation is spatially concentrated in the upper mantle for short loading periods, implying that exogenic forces may play a role in the generation of weak upper mantle layers. The results are also scaled to estimate how much energy is dissipated in Earth's mantle, both present and past, during surface mass movement processes and tidal forcing. We find that the dissipation from glacial loading cycles since Mid‐Pleistocene at a period of 100,000 years might contribute ∼3 mW/m2 heat flux in the formerly glaciated regions, but for glacial cycles with a period of 40,000 years during the Early Pleistocene, the heat flux may have been 3 times larger at ∼9 mW/m2. We find that tidal forcing for the early Earth at 4 Ga may have contributed ∼30 TW of heat to the upper mantle, suggesting that exogenic forces have the capacity to contribute significantly to early Earth's energy budget. Plain Language Summary Heat in the interior of solid planets and moons comes from three main sources: heat from formation, heat from the decay of radioactive elements, and energy dissipated as heat when mantle material is deformed by external forces. In this study, we use a simple 2‐dimensional model to characterize heat generated by viscous dissipation resulting from a surface loading force. We examine how dissipative heating behaves under different loading conditions and in materials with different viscosity structures in order to understand the general controls on dissipative heating in solid celestial bodies. We also scale our results to estimate how much heat might be generated on Earth during climate processes, such as glaciation and de‐glaciation, and during tidal deformation. Our results suggest that in some cases, heat from external forces may strongly influence mantle dynamics and even influence the dynamic formation of layered viscosity structures. On Earth in particular, heat generated by tidal forcing around 4 billion years ago was potentially of large enough magnitude to contribute significantly to interior heat and influence the dynamics of the mantle. Key Points Work done at the surface of a viscoelastic solid is always balanced by energy stored elastically and energy dissipated as heat At short loading periods, dissipation is most often spatially concentrated in weak upper mantle layers At certain times, tidal forcing and climate forced mass movement may have contributed significantly to Earth's energy budget