In an electric water heater, the inner container 1 is foamed around with an insulating layer 2. This is covered by a casing 3 and a cover cap 4 which is put on and a bottom cap. In order to stabilise the casing 3 of thin wall thickness and to prevent the foam coming out during foaming, an edge 5 is bent on the casing 3, from the outside 5' of which edge an outer rim 6 faces the cap 4. Tongues 10 of the cap 4 bear against the inside 5'' or in the corner region of the edge 5. <IMAGE>
