Voltage drop

Voltage drop is the difference between the voltage at the supply end of a circuit and the voltage available at a load when current flows through conductors, connections or other impedance. It is measured in volts or as a percentage of the nominal voltage. In home energy documents, voltage drop may appear in cable sizing, EV charger circuits, inverter AC circuits, heat pump electrical supplies and voltage-rise checks for solar PV export. MCS solar PV requirements say AC cables should be sized to minimise voltage drop as far as reasonably practicable, with the service head and inverter AC input terminals as the reference points. A voltage-drop note should be read with circuit current, cable length, conductor size, phase arrangement, equipment instructions and the relevant design limits rather than treated as proof of safety, compatibility, low losses, DNO approval, MCS certification or whole-installation compliance.