In the talk the ac transport of non-interacting electrons through the quantum capacitor is considered. It is shown that in the adiabatic non-linear regime the ratio of dissipated energy to frequency-dependent noise is independent of properties of a capacitor. In the quantized emission regime, when one electron and one hole are emitted during a period, this ratio is two times larger that in the linear response regime. On the other hand in the system of two capacitors coupled in series this ratio can be anomalously small: The particle transfer between capacitors produces current fluctuations while it does not lead to energy dissipation