The thesis deals with a comparative analysis of energy balance of public buildings before and after energy renovation. Most of the energy renovations of public buildings in Slovenia between 2010 and 2015 was co-financed by the Cohesion Fund of the European Union. The analysis is based on the calculations of energy balances of the buildings before and after renovation. The calculations were carried out by designers prior to submitting the project application for subsidy. We had at our disposal all application forms and project documentation for 33 public buildings, all of which are intended for educational activities. All calculations of energy balance of buildings carried out by the designers were performed with commercial software ARCHIMAID or Gradbena fizika URSA 4.0. The review of these calculations of energy balance shows that most of the boundary conditions used by designers in their calculations do not reflect the actual state of the buildings. The calculations carried out by designers were compared with calculations conducted with program TOST. In our calculations we used the same parameters the designers used in their calculations. The comparison shows significant discrepancies. We also analyzed the effectiveness of energy renovations of the buildings. In this analysis we reviewed whether the buildings achieve planned energy savings in kWh. More than half of the buildings achieve planned savings while the other buildings do not. It is assumed that badly conducted simulations of energy balances are a major factor why the buildings do not reach planned energy savings. A comparison of the cost of energy renovations of buildings to planned savings was made and the payback period was calculated. The end of the thesis includes a presentation of energy monitoring – a way of energy management of the building.