The installation includes all the necessary amenities for people to live there full-time. This is usually a number of residents equal to the HQ’s power level comfortably (possibly more, at the GM’s discretion). It includes bedrooms or private suites, kitchen facilities, dining area, and common living areas. Characters can live in an installation lacking this feature short-term, but they’re not likely to be very comfortable.
D20 Hero SRD Installations Article- http://www.d20herosrd.com/7-gadgets-gear/installations