The solar tube is also known as the sun tube, light tube, sun tunnel, tubular skylight and daylight pipe. It looks exactly like a tube, thus its name. The solar tube mentioned here is not to be confused withthin-film agri voltaic solar tubesandphotovoltaic solar tubeswhich are mainly made for generating electricity. These. Solar tube sizes are determined by the diameter of the tube. Sizes vary from as small as 2 inches to 48 inches, depending on brand, type and use. You can't expect solar tubes to be as bright as skylights. Solar tubes and skylights may serve the same function, but they have slightly different. Yes. On a bright day, a 10-inch solar tube can give you about the same amount of light as three 100-watt bulbs, enough to illuminate a 200 sq. ft.