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Originally Posted by bluesky2
I am looking at a Zanussi (Electrolux) ZSF 2420.
Water: 7 Litres
Washing time with drying: 94mins
Drying time: 13 mins
Energy: 0.8Kw (800 watts)
Heating Element: 1000w
Power rating 1080w.
So 800watts/230V=3.4Amps for 1.5 hours = 5.2 amp hours
So 5.2 amp-hours and 7 litres of water seems pretty reasonable.
The size is fine for two people and can fit pots and pans etc.
A couple things here. First, what they are calling "Energy" should probably be watt-hours or Kw-hours, which is the right unit for energy.
Since it has a 1000 W heating element, and a power rating of 1080 W (watts is a unit of power), its complete washing/drying cycle probably totals up 800 W-h of electrical energy.
Second, amp-hours is shorthand for energy usage from batteries at 12 volts, not 230. That 800 W-h at 12 v = 800/12 = 66.7 a-h. Xantrex gives an efficiency level of 85% for their Freedom inverters, so this would mean 78.4 a-h drawn from the batteries.
It's not insurmountable, but it might be cheaper overall to invest in a little Honda portable generator and use this to power the dishwasher directly. That'll save the need for a couple hundred extra a-h of battery bank, a big inverter, a big engine alternator and a couple extra hours of main engine use every dishwasher cycle. The little generator would also charge your batteries from regular house loads for less cost than running the engine, too boot.