Generator sizing is based on the starting amperage load of the equipment you are running. To calculate the wattage the formula - Starting Amps x Volts = Watts will assist you in calculating the correct wattage need. When looking at your starting amps on the furnace you are needing 10,800 watts plus the 3600 watts from your water heater puts you at 14,400 watts not including your well pump and home items. Rule of thumb is to size the generator to 80% of its capacity so when an item does kick in you have plenty of power available for flexibility and the voltage stays clean.Also, converting your 3-phase unit to 1-phase you lost approximately 30% of your kW (on most alternators, some are a little more and some a little less). We do recommend that you step up to the 22kW model so you have plenty of power available provided your tractor is large enough. Minimum tractor size 41 PTO HP.
Model PTO 22-S