In photovoltaic (PV) applications, it is possible to remove the transformer to reduce the losses, costs, and size. However, the conducted noise issue occurs. The conducted noise emission introduces interference to other circuits and therefore should be reduced. Conducted EMI generation mechanism in a single-phase photovoltaic system is evaluated. A balanced noise reduction method is utilized for noise reduction. The consequent of utilizing the balanced technique on the boost converter and the whole PV system are investigated, respectively. Comparing with using a noise filter, the balanced method could suppress the conducted noise from 150 kHz to 30 MHz and especially have a good performance on the high-frequency range. The analysis is verified by experiment.