An integrated water heating system is comprised of a hot water holding tank having an outer jacket secured in spaced relationship therearound. An insulating space is defined about the hot water holding tank and the outer jacket. A connecting bracket is secured to an outer surface of the hot water holding tank and has a projecting formation provided with an arcuate connecting wall spaced a predetermined distance from the outer surface for close fit adjacent an inner surface of the outer jacket and disposed for alignment with an external support bracket adapted to be secured thereto through the outer jacket. Thermal insulating material is disposed in the insulating space and about the connecting bracket. An external water heating device is removably supported by the external support bracket. A pump circulates water through the water heating device and through the hot water holding tank.