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As a data point my Foretravel had the same size aqua hot but with only 1 120vac 1650 watt element so I could keep it on with the 2 AC's running. That single 120vac element gave me hot water all day, not quite continuous long steaming hot showers but ok if we'd wait about 20 minutes between showers.
So if you can do the 120/220 split you can still take comfortable showers using just the 120vac element.