The construction industry in the Baltic countries has undergone significant transformation since the 1990s, driven by advancements in construction technologies and the introduction of new materials. However, despite these developments, most buildings constructed during this period fail to meet modern energy efficiency standards and fall significantly short of the nearly Zero-Energy Building (nZEB) requirements. This study analyzes the energy performance of multi-apartment buildings constructed before and after the introduction of nZEB regulation. The research is based on an in-depth evaluation of multiple databases, incorporating real measured data from the past five years. The analysis leverages the national energy performance certification database to compare theoretically planned energy performance with actual measured data. Additionally, data from a municipal energy agency is included for further comparison. The findings reveal that energy consumption for space heating in these buildings can reach up to 100 kWh/m2 per year, which is comparable to the consumption levels of non-renovated multi-apartment buildings constructed prior to the 1990s.