Electric power companies are looking for ways and means to overcome the problems caused by the rapid increase of construction costs of a new power plant. One of the current alternatives is to share a generating plant among two or more utilities. In the paper, a probabilistic model of a jointly owned generating unit is developed. The model is utilised to investigate the effects of joint ownership of generation on the reliability as well as on the production costs of two interconnected systems. The segmentation method is used in the numerical evaluation.