A Portable On-Site Fusion Reactor was a type of power plant available to the Federation.
This reactor assembly takes up a two-meter-square area when in operation. It runs on a pergium isotope and provides sufficient power to operate virtually any equipment or to supply the needs of a community of 10,000 people. It can be transported by a cargo transporter or in a shuttlecraft, will not fit into any ground vehicle than a medium-sized truck. One-half kilogram of fusion fuel operates the reactor for a week. (FASA RPG module: Star Fleet Intelligence Manual: Agent's Orientation Sourcebook)