The facility strategy of the City of Espoo emphasises improvements in the energy efficiency and efficient use of buildings. The design phase of a building is crucial and when the building is in operation, it is crucial to use control systems correctly. Further, in order to encourage relevant efficiency efforts, it is essential to know how to measure energy efficiency in the building operation phase. This requires an understanding of the correlation between building occupancy, space efficiency and energy efficiency. Energy efficiency is typically measured as energy consumption per unit of area kWh/m2 per annum. The specific energy consumption is an effective way to measure the technical properties of a building and to guide its design but it neglects issues related to building occupancy and space efficiency. This paper explores ways in which building usage and occupancy influences the measured energy consumption in Finnish daycare centres and school buildings. The study adopts existing energy efficiency indicators and introduces a new indicator for building energy efficiency which takes into account both space and occupancy efficiency.