With the interest to reduce electrical energy consumption there is an upcoming shift from the traditional incandescent lamps to more energy efficient types of lighting. This has raised a concern of a possible adverse effect on the power grid as we replace a resistive load with an electronic one. The main concerns include harmonic distortion, losses in the grid, and displacement power factor (cos ). A set of measurements have been made in order to determent how a shift in lamps would affect a number of power quality parameters. The measurements have been conducted on a typical household base load consisting of a mix of lamps, TV, computers, heat and kitchen equipment. The measurements have been performed in the laboratory so as to have complete control over the load. A typical consumption pattern has been defined however so as to make the measurements both realistic and reproducible. In the initial stage the installation contains only incandescent lamps; in the final stage all incandescent lamps are replaced with a more energy efficient alternative. A second set of measurements have been made in a medium size hotel, with a load of over 500 incandescent lamps. The power quality has been monitored before, during and after all the lamps were replaced by 40 W equivalent LED lamps. This paper will focus on harmonic distortion up to 9 kHz as well as the affect a shift in lamps will have on the displacement power factor and on losses in the distribution grid.