An electric boiler

An electric boiler comprising a heating element in a thermally conductive inner container, the inner container substantially surrounding the heating element to define an inner passage about the heating element, the inner container having an inlet and an outlet for a flow of water and being arranged such as to cause water received at the inner container inlet to flow along the inner passage, in close proximity to a surface of the heating element to the inner container outlet, the boiler further comprising an outer container in which the inner container is substantially located, the outer container defining an outer passage extending around at least part of the inner container, the outer container having an inlet and an outlet for a flow of water, wherein the outer container outlet is connected to, or forms, the inner container inlet and wherein the outer container is arranged such as to cause water received at the outer container inlet to flow along the outer passage in close proximity to a surface of the inner container to the outer container outlet.