The present invention relates to a hot water storage tank (202, 302, 402, 502, 602, 702), defining a primly storage volume (204, 304, 404, 504, 604, 704), with at least one heat source (212, 312, 412, 512, 612, 712) positioned in and operable to directly heat water in the upper portion (207, 307, 407, 507, 607, 707) of the primary storage volume (204, 304, 404, 04, 604, 704), and a pump or other means (237, 337, 437, 537, 637) that draws water, from the lower portion (209, 309, 409, 509, 609, 709) of the tank into a heat transfer device (216, 316, 416, 516, 616, 716), situated in said upper portion (207, 307, 407, 507, 607, 707). The heat transfer device (216, 316, 416, 516, 616, 716) is configured to enable the transfer of heat from heated water in the upper portion (207, 307, 407, 507, 607, 707) to the drawn water prior to discharge into the water in the upper portion (207, 307, 407, 507, 607, 707).