Getting hot water in a Sprinter with a D2L installed

There are two options:

1. A calorifier can be connected to the engine loop or to an Espar Hydronic D5E. The D5E would run an independent coolant cycle and heat coils inside of calorifier. The calorifier can also be hooked with 12V and 110V combined immersions, which would allow to use up any extra solar power to heat water.
2. A water plate exchanger can be connected to the engine loop or to an Espar Hydronic D5E. This system would run "on-demand", so it takes few minutes for the system to heat up. While this solution uses less space, it requires more plumbing.