More wire size confusion - Inverter, bus bar and battery


New Member
Mar 12, 2022
Kansas City, MO, USA
I am putting together a 400w Renogy kit. I got a 1000w Renogy inverter and it came with 4 AWG wires. I am outputting from the 40a SCC with 8 gauge wire to the bus bar. If I hook the inverter to the bus bar, doesn't that mean my bus to battery connection also has to be 4 gauge? and would a 100 amp fuse be enough to be between battery and inverter?

Or should I just hook up the inverter directly to the battery with the included 4 gauge cables and leave everything else to go thru the bus bars?


Apr 24, 2020
Somewhere South of Denver
Yes, the cable run from the inverter all the way back to the battery needs to be 4 awg. You can always run bigger cable, nothing wrong with that as long as the cable fits into the inverter's terminals. If the distance between the inverter and battery is long then bigger cable is warranted to avoid voltage loss. Use the voltage drop calculator below to know for sure.

A 1000 watt inverter running at 85% efficiency at nominal 12.8 volts will draw 66 amps (1000 * .85 / 12.8). Add 25% to avoid nuisance trips and you get 83 amps. So a 100 amp fuse will work. Plug in revised numbers to the formula as needed.

I would use the common bus bars for connections. The power from the solar charge controller doesn't always go to the battery. The inverter can consume every watt that the solar charge controller produces.

Don't forget fuses on all the other wires. Over Current Protection is for the wires, not the equipment.