The Webasto is more or less easy but just very time-consuming. You have to position the device in a good spot in the engine bay, route the water or coolant lines to it, route the electrical and control cables and that's it. All is a step-by-step process but if it's to be done right, expect to spend many hours installing it. If you give the job to someone it will be done probably in a hurry.
Normally the Webasto heater should circulate coolant which heats up the engine, then the cab fan turns on to heat the inside of the car. This is the proper, standard way of operation, but I don't need a warm engine (my petrol engine starts in every climate), I don't need hot air in the car. I just need hot water. Therefore my heater is fed water straight from the tank, then the water returns warmed up. So there is an outlet from the tank to the heater, and a return line. A 12V rotary bilge pump recirculates all that water.
This tank has fresh water which is used for cooking and washing but I do not drink it as it is. I prefer to boil it or simply have some bottles of mineral water. The tank is in a warm place and without access to sunlight so bacteria are there. Probably harmless quantities but probably not, so I am not taking risks. If I were to drink this water I would place it in a transparent bottle and leave it in the sun for a few hours (SODIS).
I have a petrol engine which, in spite of being rather big (4.5L) requires little power to start. It starts with batteries as small as 50Ah and I have a 70Ah as the engine battery. Just one. It is used only for driving so I am not afraid of low power. I have the second battery 100Ah for all the leisure stuff and this one is connected to the solar panel.
The solar panel is attached with some brackets which are originally for CB radio antennas. They look like this:
Small allen screws fasten the bracket to the hood and the big hole goes to the panel frame.
