We have the Hydro Hot. When we arrive at the campground the water is already hot. Plenty of hot water for 2 people for the night. If we're staying a few days, we turn on the electric element. When we have more than 2 people, are camping in frigid weather, or higher demand, we do use the diesel. Of course, we use the diesel when dry camping.
Note: If we're at our daughter's house we don't use the electric because it increases her electric bill. The diesel boiler will heat the water in about 10 mins so we turn it on before shower time. Once our showers and dishwashing are done, we turn the diesel off.