[Pam Asks]  For a 220 volt well pump, how do you calculate the wattage needed to operate it?  I am trying to figure out if I can use a solar generator to run the pump for short durations during the day for showers, irrigation, clothes washing, etc.

[Justin]  The pump should have a label on it describing its operating parameters. If not, get an Amp meter, or find someone who has one, and measure while it’s running. The calculation is simple: Watts = volts x amps.

Wattage is often also called volt-amps or VA.

[Paul]  There’s another tricky part about determining if you have enough capacity to run a well pump….and that is that pretty much all motors (pumps, air conditioning compressors, even compressors in refrigerators, the list goes on) have a start-up surge requirement…..so while your well pump might draw 5 amps of 220v current when its running, it might need (and I don’t know about your pump) 15 amps of inrush current to get the pump motor started….that start up current could last for any number of seconds while that motor is starting up…..  Truly the only way to figure that out accurately is to put a meter on that circuit and measure both those surge amps and the running amps.    The various models of solar generator devices often have some level of surge current capability, but its all over the map as to whether their inverter actually does what they claim, or comes close to it, or will last long enough to get your motor started… you’ll run into this same issue even with a gas powered generator…