I have a heater coil (purely resistive) of resistance say R. If I hook this resistance to the mains, I get power of V_source_rms ^2 / R. I don't want that much power. So, I use some power electronics switching device, and hence reduce the effective V_load_rms to a lower value. So, my new output power is V_load_rms ^2 / R. such that, (V_load_rms < V_source_rms) Now, From the point of view of source, the Load power factor = P_load / VA_source = V_load_rms * I_load_rms / (V_source_rms*I_source_rms) Since, there is no other paths for current, I_load_rms = I_source_rms Therefore, PF = V_load_rms/V_source_rms So, it appears, If I want to consume reduced power by using the same heater, by method of switching, then my power factor becomes poorer. Is there any way I can avoid it, or can compensate for it? thanks.