Patrice,
"Shirley Valentine" was launched in Koper. Slovenia in Feb 2010. We sailed "Shirley" as live-a-boards for 5 1/2 years in the eastern Med. In May last year, we shipped her from Genoa to Australia. We now keep her on our pontoon on the Gold Coast, Australia.
In regard to the comments about heating water, we looked at a 800w element to run from our 1000w generator. That is, heating the water, then turning off and charging the batteries. For most yachties, this is probably not optimal. If you install a 800w element, you can not start charging the batteries until the water is heated, then the batteries are typically charged at a maximum of 40amp ( about 480w) but quickly dropping once more than 75% charged. This means that your 1000w generator is charging at well below its designed capacity when charging the batteries through your 240v battery charger.
By installing a 500w element, you can heat water, admittedly at a slower rate, while charging your batteries. By the time your batteries are typically charged ( this will depend on size of battery bank and state of charge) you will have ample hot water. On our boat with 340amp/hr battery capacity, the water is always fully heated in less time than it takes to charge the batteries from 50% capacity to about 80% capacity. We have limited solar capacity as we didn't want to install a Targa bar with large panels. We have semi-flexible panels that we can walk on, mounted on the deck in front of the spray hood. We can go 4 days without needing to charge the batteries in typical Med conditions. Usually we move by then. We typically used our generator less than 4 or 5 times a year. For typical Med conditions, I believe a generator ( and water maker) to be fairly useless. This is not the case elsewhere.
If your solar panels keep your batteries close to fully charged and you only need to heat water, then install a 800w element.
The hot water capacities in boats is typically from 15 litres to over 30 litres and is kept at a temperature too high to bear. I don't know the exact temperature but suspect that, as the water is heated from the engine cooling water, it could reach temperatures over 80 degrees centigrade. This will burn you. Typical, comfortable temperatures to shower in are around 35-40 degrees. This means that you will not have to heat the water much to have a reasonable shower, but you will have less hot water thereafter.
Hope this helps
Craig
"Shirley Valentine"