A solar heating apparatus comprising: a first longitudinal space for holding water; a second longitudinal space for allowing upwardly flow of water being heated, located parallel to the first longitudinal space and substantially thermally separated therebfrom; passage means for allowing flow of water from the bottom portion of the first longitudinal space, to the second longitudinal space and heated water from the second longitudinal space to the top portion of the first longitudinal space, wherein the first longitudinal space equivalent cross section is substantially larger than that of the second longitudinal space, wherein the two longitudinal spaces are integral portions of the solar heating apparatus, and wherein the apparatus is adapted to be installed so that the second longitudinal space is located at a side that would be heated up by incident solar radiation absorbed by a solar collecting plate, thereby heating of water flowing through that second longitudinal space.