Electrocaloric materials are promising working bodies for caloric-based technologies, suggested as an efficient alternative to the vapor compression systems. However, their materials efficiency defined as the ratio of the exchangeable electrocaloric heat to the work needed to trigger this heat remains unknown. Here, we show by direct measurements of heat and electrical work that a highly ordered bulk lead scandium tantalate can exchange more than a hundred times more electrocaloric heat than the work needed to trigger it. Besides, our material exhibits a maximum adiabatic temperature change of 3.7 K at an electric field of 40 kV cm-1. These features are strong assets in favor of electrocaloric materials for future cooling devices.