The heat power production by the 0,25MWe biogas-works was compared with the calculated heat power demands for the 500 ha farm in the climatic conditions of Wielkopolska region, for the consecutive months of one year. There was an analytical investigation of the effect of the temperatures changes: normative, monthly mean for long-terms and monthly minimal mean for long-terms - for the heat power demands for the heating farm buildings and rooms. It was stated that the calculated heat power demands change significantly in the consecutive months and is very dependent on the external temperatures. The higher heat production by biogas-works in the summer months and the lowering of heat power demands observed from January, very low in summer, then increasing to December, cause very high heat power surplus, especially from May to November. The calculation of heat power demands, very strongly depend on external temperatures and those obtained for the normative temperatures are hardly useful for the planning of the use of the dynamically produced heat power by biogas-works and its demands in the farm.