This work looks in detail at two cogeneration plants with different operation regimes. First one is operating whole year according to winter and summer load curves, second one – only in heating season, because consumer have only heating load. Both plants have natural gas fueled internal combustion engine facilities. Cogeneration facility operating data analysis showed that their efficiency is 84% and 85%. This means that plants operation is done according to requirements of Latvian legislation on cogeneration. It is estimated that cogeneration plants are operating with appropriate electricity versus heat rate. Also number of operating hour per year is calculated and solutions for improvements in the plants are given.