rocketmrv I am not sure. Mine came without any sort of instructions or even specs. It is supposed to have a built in regulator (model is an updated version distinguishable by a green led on the main housing) but there is three wires output. I am yet to install, but assume the three wires must carry two phases of AC current. I will test before installation and if AC I will test voltage and rectify and regulate to about 14.4 volts so as to not cook my batteries. (unlikely since I have 600 amp hour batteries installed.) Can anyone help us out with further information? I doubt the output is 4000 watts as described in my version. I even doubt the 1000 watts given the size of the unit. If three wires output assume unregulated, unrectified. Test with a simple DMM (digital multi-meter) after installation. If AC it will need rectification and maybe regulation. Recommend bridge rectifier and solid state voltage regulator (14.2 or 14.4v) with pass transistor if required. (about $5 all up) Alternatively, the three wires may be red +, black - and green earth. If it produces under 14.4 -15 volts on black and red wire with no voltage on green wire then is ok to install as red+ (to battery), black - (to battery) and green to an earth stake in ground. (I am old school) Hope this helps.