In order to achieve national, European and international energy goals, energy efficiency strategies in the building sector have to be implemented. The passive house standard and low energy standards are already successfully established in single dwelling houses. These high performance standards are starting to penetrate into the sector of housing associations. A case study about an apartment building constructed by a housing association is presented here. It describes the monitoring concept and the results of the 1st year of monitoring. Depending on the definition of the zero energy building standard (extent of loads included in the balancing), the building could be classified as an energy plus building or as a building, which uses more energy, than is supplied by on-site generation. If the building's total energy use (including user specific loads) is defined as load, only 34.5% of these loads were provided by the net energy output of the PV system. If only the heating energy demand is defined as load, the PV system even yielded a surplus of 45.6% of the energy load. (C) 2012 Elsevier Ltd. All rights reserved.