I called a popular well drilling and service company in my town and asked them about generator size. I told them I had 425ft well with a 1.5hp pump and they said "take 13 amps x220 volts=2860 watts, add about 25% for start up, about 750 watts, for a total of 3612 watts minimum for generator size". They said "minimum, bigger is better". There are 4 wires going down into my well, marked red, green, black and ground. I'm hoping all that is correct, but they are supposed to be the experts! So I guess a 3KW ST head won't do it, but a 4 or 5KW would?