Glossary Voltage Drop
A plain explanation of voltage drop for anyone outside the electrical trade trying to understand why it matters.
Voltage drop is a concept every electrical professional understands intuitively but sometimes struggles to explain plainly to a client or non-technical stakeholder. Here's a genuinely non-technical version.
Think of voltage as water pressure and current as water flow. A long, narrow pipe loses pressure along its length due to friction — by the time water reaches the far end, the pressure available there is lower than what started at the source. Voltage drop is the electrical equivalent: resistance along a cable's length "uses up" some of the available voltage before it reaches the load, leaving less pressure (voltage) available to actually do the work at the far end.
A load designed to run on, say, 230V doesn't perform as intended if it only actually receives 215V at its terminals — motors run less efficiently and can overheat, lighting dims, sensitive electronics can misbehave. Beyond performance, sustained voltage drop wastes energy as heat in the cable itself rather than useful work at the load.
Just like a longer pipe loses more pressure, a longer cable run accumulates more voltage drop — which is exactly why long feeder runs get special scrutiny in every code, and why voltage drop is checked as its own independent step, not assumed to be fine just because the cable's ampacity is adequate.
Engr. Jason Morales — Founder, SolarEnergyPH & OhmWorks