What size sump pumps. Most of our sump pumps at work are around 5hp 3
phase 480v. Most generac's are only single
phase home generators. At one time generac commercial units were kohler generators coupled onto cummins diesel engines. Most smaller generac's with the little kohler engine have been known to blow up around 50-100 hours. Our fire departments use 25k cummins generators. They are powered by natural gas burning ford v-6's (pretty ironic to see a ford coupled to a cummins) but they work great and parts are easy to get. Also keep in mind there are hybrid and bi-fuel generators. They hybrids work like the cars. The genset charges a bank of battery's mounted onto the genset skid where the fuel tanks normally sit. The load is connected through an inverter to convert the battery
power AC. As the batteries discharge and charge the generator will turn on and off respectively. It's a nice design providing very clean true sinewave
power. The bi fuel generators will run off utility natural gas but if the natural gas supply is interrupted it will
switch to running on diesel fuel. They can
switch back and forth between diesel and natural gas without interruption. Also there are hydraulic powered pumps available also. The hydraulic pumps are driven by diesel powered engines, but while utility
power exists
electric motors drive a hydraulic pump. The diesel and
electric powered hydraulic pumps are two separate pumps incase one fails there is a backup. Also keep in mind pumps are not generator friendly. They will pull twice to three times their normal load when starting. (we have to synchro start all of our pumps or we will trip breakers). I know my little 3hp well pump makes my 7kw generator jump every time it kicks on so definately keep your starting
load in mind. Look up locked rotor amps for a guide on actually how many amps a motor pulls when starting up, it's mindblowing.