We have the upgraded larger Aqua-Hot system with the two heating elements. Over the last 7 yrs. it seems the single heating element makes plenty of hot water for two showers. When I turn on the both elements, wow, we have really hot water and have never run out.
If it's not too cold out, let's say in the lower 50's, I can heat the coach through the Aqua-Hot system with the eletric elements (bringing the inside to 65-68 degrees).
One thing I should point out, heating with one or two elements will depend on the incoming temperature of the water. We were just in Colorado and I had the two electric elements on and noticed I had to turn the shower position more towards the hot to get good warm water. Then it hit me, while I was outside earlier, I washed a towel out that I used to wipe off the front cover of the Honda, I remember the water being so cold it kinda numbed my hands. So, the incoming water temp can make a difference on how quick the water will heat.
MM.