Its more about duty cycle to be fair. My Thermalarc 175 will do about a rod and a half and wait a while and it'll do it again. My diesel welder will burn them in hot all day and not get too far above idle.......Hi lads just out of curiosity what size welder would I need to burn 4 mm rods .
My preference would be an oil-cooled machine, if you're in the workshop, no problems with duty cycles. Trouble is, to run the kinds of current 4mm rods need you'd need a 3 phase supply. I don't know much about inverters but if you can find one that handles the kind of current, suggested by @Memmeddu, with a decent duty cycle you might get away with a dedicated 20 amp circuit on single phase.
My inverter will stay in the 13A only if under 100A output current.Many DC inverters of around 200 amps or higher will easily handle them and 5mm.
You have a choice of DC invertor machines running off 240 single phase around these currents, albeit over 13 amp input.
My preference would be an oil-cooled machine, if you're in the workshop, no problems with duty cycles. Trouble is, to run the kinds of current 4mm rods need you'd need a 3 phase supply. I don't know much about inverters but if you can find one that handles the kind of current, suggested by @Memmeddu, with a decent duty cycle you might get away with a dedicated 20 amp circuit on single phase.