This paper presents the design considerations and the design procedure for low and medium power electrostatic energy harvester. First, the principle of electrostatic harvester is discussed then the design considerations are analyzed and assessed. Our assessments indicate that the electrostatic generator requires motion energy at low frequency to achieve higher power generation. This motion produces a higher power per unit volume in comparison to the vibration. The best material that can be used for the electrodes is silver as it has a higher conductivity, reliability, stability and it can handle high voltage up to 100 V when compared to the other common capacitor materials. The in-plane overlap realization method can be considered to be a suitable choice when applied to variable capacitor machine. With regard to the conditioning circuits, the switched capacitor regulator is the most appropriate option as it can solve the sizing problem and provides solution for the up or down conversion of voltage when comparing it with the other conditioning circuits. Finally, we propose a general electrostatic harvester design procedure according to the addressed designed considerations.