Yes the correct wattage is based on room size. To find the proper ambient lighting for the room, multiply the room dimensions to get your total square footage (12 x 16 = 192). Then multiply the total square footage by 1.5 for total illumination needed (192 x 1.5 = 288 watts). Remember this total can be achieved by several methods of lighting. You are better off spreading the wattage around than have it all come from a single light source. Remember too that if the space is workspace, additional task lighting may also be called for in certain area(s) of the room.