While the multi effect distillation desalination industry has made definite strides in terms of improving efficiency, the potential of low-grade heat sources and renewable energies remains overlooked. Although the basic principle remains the same, the nature of sensible heat sources requires different optimisation approaches than conventional steam driven systems. We hold that the conventional performance measure is incongruent with such applications and posit a new benchmark. We demonstrate this with the optimisation of multi effect distillation systems, so that freshwater yield can be improved by up to 40% for both conventional and advanced systems. This modus operandi significantly stretches the viability of multi effect distillation, and rejuvenates the potential of waste heat streams. © 2013 Elsevier B.V.