The PUR/Katadyne made about 30-35 gallons per day, depending upon voltage. I would run it for about five hours per day and supported my whole system with about 330 watts worth of
solar panels. The
watermaker drew 4 amps at 12 volts, so its total draw was about 20 amp hours per day. It was always easy to run off the
batteries, whether the sun was up or down, or the
engine on or off. I did not have a
generator on that
boat.
Currently, since we are a good sized
charter cat, we have a 9KW NorPro
generator. The Spectra
Catalina, 300 gpd, would actually make that amount, or a little less, depending on the state of charge of the
batteries. Our
battery bank is large, 900 amp hours, and the
watermaker would happily run all night ( or day) on
battery power alone.
Current draw was about 16-18 amps and it was very nice not to have to run any engines or generators in order to make
water. Recently, we replaced the smallish Bodine
motor with a much larger, and slightly less efficient Leeson, and we upgraded the
pump head to a size that is rated at 400 gpd. It will actually make that amount off the batteries, but draws 24-26 amps so will not run all night on its own. The problem is not with the overall draw, but that the
current causes a voltage drop, while running, that activates our low voltage cut-out after a few hours. However, the cut-out is cutting out at too high a voltage, so I am about to sort that out. At that point, I would not be surprised to see the unit run all night, if necessary. Of course, as the voltage drops, so does the output, but at its lowest, it still gets 14-16 gallons per hour. If the generator is running (and the batteries are being charged, we have seen as much as 18 gallons per hour. We do coordinate the watermaker use with the genset, but since we have to make about 12 hours of
water per day while on
charter, we do run off the batteries quite a bit. It should be noted that both the Pur and the Spectra are extremely efficient units, and most AC driven units use as much as ten times the
power per gallon. Hope this helps.