**There are two important limitations:**

**First**, the high withstanding voltage required of the capacitor, along with the high-capacitance required for a given output current, mean that this type of supply is only practical for low-power applications. (The capacitance needed increases with the current to be drawn; high capacitance mains-voltage capacitors are expensive and bulky.)

**The second** is that due to the absence of electrical isolation between input and output, anything connected to the power supply must be reliably insulated so that it is not possible for a person to come into electrical contact with it.[1][2] By the equation of state for capacitance, where {\displaystyle I_{c}=C{\frac {\mathrm {d} V}{\mathrm {d} t}}}

, the current is limited to: 1 amp, per farad, per volt-rms, per radian (of phase). Or {\displaystyle 2\pi }

amps, per farad, per volt-rms, per hertz.