A power system makes the installation completely independent of outside power. It has its own generators (which may be solar, geothermal, nuclear, cosmic, or anything else the designer wants). They provide the base’s entire power needs. The installation also has emergency back-up power should the generators fail. This generally lasts for a number of hours equal to the HQ’s power level.
D20 Hero SRD Installations Article- http://www.d20herosrd.com/7-gadgets-gear/installations