solar water heater

We use our WH in the morning and in the evening. I turn it on for 15-30 mins (evening takes less time) each time. We shower at night before bed. Makes for a more comfortable sleep. You know, what I'd like more than battery capacity is FW storage. 200 gallon FW and grey tanks would be perfect. Could camp comfortably for a month. My next rig will have those size tanks even if I have to custom install them.