Evaluation of one of the most important technological and organizational conditions, that is accumulation of labour inputs, at introduction of energy crops into the existing agricultural systems was conducted. For that purpose the simulation method with the use of a farm model was applied. It was assumed that the production plan of the farm consisted of four food production technologies (winter wheat, winter rape, spring barley and maize for grain) with the acreage of 20 ha each grown in monoculture. Energy crop (willow) was introduced by replacing the least-profitable crop grown heretofore. The farmer and hired workers provide the labour resources. The analysis of the labour input accumulation was conducted over decade periods, into which the calendar year was divided. It was found out that replacing the least-profitable plant (winter wheat) with energy willow did not lead to an inadmissible labour input accumulation. For the assumptions made, the replacing of winter wheat with energy crop can be a profitable strategy.