This thesis was commissioned by Forest Management Association Pirkanmaa in co-operation with the Naistenlahti power plant in Tampere. The aim was to determine the average energy content of spruces with rot, which are unsuitable for pulp and saw industries. The determination of the energy content was necessary because its exact value is not known and the energy wood market price is determined on the basis of this information. The energy content was determined of rot root logs from harvesting sites in Metsänhoitoyhdistys Pirkanmaa region. The rot root logs, which are cut to 3 meter length, are an essential product, which is harvested in quite significant quantities from aged forest logging sites. It is used for energy production as wood chips. In this study the methodology and standards meant to determine the energy content were applied, such as wood chips moisture content (%), calorific value (MJ / kg) measurement, wood volume and weight. The energy content was calculated from these measuring results. The study consisted of two lots of wood; the first one from Forest management Association Pirkanmaa logging sites and the second one from Luvia Saha Oy logging sites. The studied wood material was collected from a large area and the sampling included different stages of rot wood. The wood material was shipped to energy wood terminal in Naistenlahti power plant in Tampere. The samples were taken and the measurements made within the normal quality control. Seven chip samples were taken from every truck load. From these samples the moisture content was measured by using the wood's wet and dry weight values. The calorific value was also measured from the same samples. The measuring took place in Jyväskylä at Labtium Oy laboratories. The volume and weight were measured already as the wood was harvested and transported. The average energy content of rot spruce wood chips was 3,05 Mwh/t and energy density 0,72 MWh/i-m3. According to this study, compared to its density the energy content of this wood chip material with rot is 7,8 % lower than wood chips with other similar properties.