On Demand Fuel Cells (ODFC) is a plugin to support fuel cells that only generate power when it is needed, thereby saving precious fuel. Simulates fuel cells in Kerbal Space Program (KSP), and do a better job of it than stock's use of a resource converter. The main difference is it only generates electricity when it's really needed (batteries almost empty), and otherwise lets electricity of a craft float up and down, as it might in a solar powered vehicle when the sun is eclipsed by another celestial body. It also allows fuel cells to generate byproducts, aimed at supporting life support mods like TACLS.