The paper presents the first off-grid system designed to supply electricity to the equipment mounted on components of the district heating network in district heating chambers. The proposed off-grid system is equipped, among other things, with a turbine and a generator intended for electricity production. On-grid power supply is a common way of providing electricity with strictly defined, known and verified operating parameters. For off-grid power supply, however, there are no documented testing results showing such parameters. This paper presents selected results of tests and measurements carried out during the operation of an off-grid supply system powering the equipment installed in a district heating chamber. The values of voltage obtained from a turbine-driven generator are analysed in detail. The analysis results can be used as the basis for further works aiming to optimize the off-grid system of electricity supply to devices installed in district heating chambers.