i have easy access to a 220 volt 30 amp circuit in my garage, while adding a 40 amp circuit would require a somewhat tedious 75 ft run of new wire. I looked at the Siemens VersiCharge manual, and although it recommends you connect it to a 40 amp circuit, there are words indicating you can make an internal adjustment to limit output in order to accommodate power limitations of older buildings. I took that to mean you can utilize the same charger on a 20 or 30 amp circuit. Having that flexibility is advantageous for me as I may not live in my current house much longer, and I would like to have the option of taking my charger with me to a new house where I do have access to a 40 amp circuit. I called Siemens technical support, and the rep confirmed the unit can be adjusted to work on my 30 amp circuit, but he told me more than once, adjusting output to 75% (i.e. 24 amps would void the warranty. No explanation why. I find it interesting that they would incorporate an adjustment that voids the warranty. Has anyone on this forum done this, and has it worked well for you? Thanks in advance.