Older residential wiring is substandard when compared to current requirements. In most cases, it implies major changes such as total rewiring or replacement of the service panel.  

The most common and apparent shortcomings with older electrical systems involve walls outlets specifically the absence of grounding and the shortage of available receptacles.

Ungrounded outlets increase shock hazards and may expose electronic equipment, such as computers, to possible damage. When the outlets are the old 2 prong type the absence of grounding is obvious. But in many homes old outlets have been "upgraded" to 3-prong type receptacles, without actually been grounded. Users are thereby given a false impression that outlets are safely wired to the ground.  When outlets are sparsely provided, occupants are inclined to use extension cords and other drug-store devices in ways that may overload circuits and create fire hazards. 

Another common shortfall in older systems is the inadequate size of the main service. Homes built before the mid- 1950s were not designed for so much power demands we currently use - dishwashers, air conditioners, etc. In very old systems especially those with fuses, overloading is common, and upgrading the main panel is required.