In the world, space heating in buildings is one of the major drivers of the energy demand. It is estimated that around 40% of all the households require space heating during some part of the year. Current stricter building regulations and increased renovation of buildings will involve in a heating reduction. As a result, the heating systems in buildings need to be analyzed and optimized in order to identify potential energy efficiency measures. In Sweden, hydronic radiators are the most common form of heating system. According to previous studies radiators in older buildings are often oversized, which enhances opportunities to improve the heating system and become more energy efficient. 

In this study, a comprehensive power and energy analysis for a multi-storey commercial building located in Gävle, Sweden has been conducted. The building was built in 1967 and features a brick façade. The ground floor is composed of double-glazed insulated windows, while floors 1 to 4 are fitted with triple-glazed windows. The building houses three ventilation systems equipped with heat recovery units, each of the systems has its own heating coil. The purpose of the thesis was to investigate the building's heating system, its hydronic radiators and potential efficiency measures. The information for the building has been primarily provided by the property company and also from Gävle Municipality. Site visits have enabled measurements and identification of design of the system and the model type of the radiators, which has helped in the calculations. 

The result that could be found in the study was that the maximum power output from the hydronic radiators covered significantly more than the maximum power losses. The findings indicated that there was potential to optimize the radiator heating system. An alternative measure is to lower the mean temperature difference in the radiator system from 50°C to 40°C. It reduced the maximum power output from 171 kW to 130 kW. Lowering the system temperature also enables the property company to achieve energy and cost savings. Additional measures such as retrofitting windows, replacing thermostatic radiator valves and lowering the indoor temperature, demonstrated potential reduced power demand and energy use.