NOVELTY - The apparatus has a light-transmitting outer cover (5) provided on a housing (H) adapted for mounting on a building so that light enters the housing. A solar fluid heater is disposed on the housing in a manner to absorb solar radiation for heating a working fluid e.g. water, and to allow some light to pass through the housing into the building. The heater has solar collectors comprising solar collector fins (7) e.g. Sunstrip (RTM: Not defined) solar fins, extending across dimensions of the housing to provide open spaces (S0) through which light can pass into the building.    USE - Used for positioning on a roof or wall of a building e.g. home, apartment, garage, office and factory, to provide solar heated water to a water heater of the building while providing interior lighting.    ADVANTAGE - The apparatus provides dual benefit of collection of solar energy for heating a working fluid and transmission of light into a building to provide interior lighting. The solar heater has set of solar collectors arranged relative to one another or to the housing and defining open spaces for transmitting light into the building, thus reducing heat transfer losses in operation of the apparatus.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a combination of a fluid heater and a set of the skylight/solar fluid heating apparatus    (2) a method of using solar energy comprising disposing a solar fluid heater on a housing that is mounted on a building    (3) a combination of a set of solar fluid heating apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a skylight/solar fluid heating apparatus.    Housing (H)    Open spaces (S0)    Light-transmitting outer cover (5)    Optional interior glazing sheet (6)    Solar collector fins (7)    Fluid inlet conduit (9)    Fluid outlet conduit (10)    Grooves (11)    Fluid conduit sections (12a)    U-shaped fluid conduit sections (12b)    Optional foam thermal insulation layer (13)