It only raises the temperature about 30 degrees so the only time you might get the recommended 120 degree minimum hotwater is when the storage temperature is 90 degrees and above. If it is 70 degree water in your holding tank the best you might get is 100 degree water. That's pretty luke warm but warm enough for a shower. For dishwashing you might do like tent campers and boil a pot of water on the stove.
2021 Advanced RV 144 custom Sprinter
2015 Advanced RV Extended body Sprinter
2011 Great West Van Legend Sprinter
2005 Pleasure-way Plateau TS Sprinter