Power electronics devices are widespread in diff erent engineering systems for housing and public utilities. But they have negative impacts on the power source. A typical example is using of the pumps, operated by variable frequency drive, in boiler stations and heating substations. The using helps both the energy savings and the electric power quality declination. If boiler station is supplied by emergency generator the electric power quality declination signifi cantly increases. Electric power quality parameters are analyzed using a simulation model, built in MATLAB/Simulink, in diff erent situations. The recommendations to ensure the specifi ed electric power quality in the electric power system are created.