In non-technical terms, low impedance means the electric fence charger is designed to effectively shock through vegetation and other foreign matters contacting the charged wire. Vegetation such as grass, weeds, vines, etc., contacting the charged wire tend to impede or stop the flow of electricity by "grounding out" the fence. This is a common problem which exists on most electric fence installations.The low impedance fence charger is a solid-state capacitor discharge design and has enough power to force the shock through vegetation. It is recommended that the charged fence wire be kept clean of all vegetation, etc. to ensure maximum performance from your fence charger.