This paper discusses the sensing of physical variables used in smart grid power mod- eling. In the applied distant power sources, we measured the interdependence between physical variables such as lighting (in the photovoltaic power plant) and water level (in the hydroelectric power plant). The data were transferred via a DA4 datalogger, which used the GPRS; the data represented physical variables stored in an SQL database. In our 24 V smart grid, the power obtained from a power source was measured. In the hydroelectric power plants was problem with non-harmonic voltage and current generated turbine. The module designed for accurate power measurement included an analog multiplier, and it was powered — together with the datalogger — by a small photovoltaic panel. Functionally, the module was directly connected with a cable to a PC hosting the Compact Rio program. The last of the renewable energy sources utilized was a battery-powered, self-charging wind power plant.