What gauge wire from battery to inverter?
The battery-to-inverter run carries the highest continuous current in your whole system. Undersized wire wastes energy as heat and is a genuine fire risk; oversized wire wastes money and patience. This is the wire to get right.
Sizing is not just about ampacity. Voltage drop over the run length matters just as much: at high current, even short runs lose real voltage, and inverters shut down early when their input sags.
How it works
Two constraints, take the stricter: the wire's ampacity must exceed the circuit's protected current (fuse rating), and the round-trip voltage drop at continuous load should stay under a small percentage of system voltage. Round-trip means both conductors - a wire run's length counts twice.
Copper beats aluminum on conductivity per gauge; temperature derates ampacity; and higher system voltage shrinks everything - the same power at 48V needs a fraction of the copper cross-section that 12V does. When in doubt between two gauges, the larger one buys efficiency and cooler terminals.
Common questions
What happens if the wire is too small?
It runs hot, drops voltage under load, and can trip the inverter's low-voltage cutoff during surges even with a full battery. In the worst case, insulation fails. Heat and sag are the telltale symptoms.
How much voltage drop is acceptable?
Common practice keeps the battery-to-inverter run very tight, a low single-digit percentage. The builder computes the actual drop for your components and distances rather than a rule of thumb.
Does the inverter's AC output wiring matter as much?
It matters, but AC output runs at much higher voltage and lower current, so it is ordinary household-gauge territory. The DC side is where the big copper lives.
Copper or aluminum?
Copper, for DIY battery wiring. Aluminum needs larger gauge for the same current and unforgiving termination practices; the savings are not worth it at these lengths.
Enter your components and cable run distances in the builder to get computed wire gauge and voltage drop for every segment.
Open the builderThese guides are educational and qualitative on purpose - the numeric answers depend on your exact components, and the builder computes them with every formula shown. Always verify a final design with a licensed professional.