Voltage Drop Calculator
Calculate voltage drop over a DC cable run and check whether the conductor size keeps losses within the usual 3 % limit.
Results
Why voltage drop bites low-voltage systems
Drop is a fixed number of volts for a given current, distance and conductor. On a 48 V system a 1 V drop is 2 %; on a 12 V system the same volt is over 8 %. That is why long low-voltage runs are the classic source of underperforming off-grid installations.
Reading the result
Three per cent is the working limit for the main array and battery runs. If the answer is above it, the fix is a larger conductor, a shorter run, or moving the system to a higher DC voltage — and the last option is usually cheapest at design stage.
Common mistakes
Measuring one way instead of both. Current travels out and back, so the length in the formula is twice the distance between the two ends. Halving it is how a 6 % drop gets recorded as 3 %.
Questions people ask
Does drop matter on the AC side too? Yes, but far less: higher voltage means the same wattage is carried at a fraction of the current, and drop scales with current.
Is aluminium cable acceptable? It is used on long runs, but its resistivity is about 1.6 times that of copper, so the conductor has to be correspondingly larger.