Cardassian-built reactors were based on a series of carbon reaction chambers, which used laser-induced fusion. According to the specifications for Cardassian fusion reactors, the operating efficiency was acceptable at as low as twenty percent peak efficiency.
In 2369, Chief O'Brien conducted a diagnostic of Deep Space 9's fusion power plant. The results were found to be thirteen percent below normal, well with Cardassian specifications, but not O'Brien's. To increase operating efficiency, O'Brien increased the deuterium flow to the carbon reaction chamber by five percent, while at the same time observing the exhaust fusion temperature. (DS9: "The Forsaken")