Pressure to slash CO2 emissions continues to mount with growing levels of legislation and incentives to preserve our environment. To meet these targets, considerable research into renewable energy sources and energy efficiency is underway. Thermal energy storage (TES) systems offer attractive properties, enabling economical energy utilization within the built environment. Phase change material (PCM) has become a forerunner in the TES field due to its high-energy storage densities (∼10 times that of concrete). An extensive review of PCM technology has been undertaken with specific attention to TES applications within the built environment, assessing the capability of PCM.