If uncertain as to whether or not to upgrade the wiring on a home, have an electrician perform an electrical inspection. In homes over 40 years old, upgrading can improve safety. Another indication of the need for an upgrade is if the home does not have enough electrical outlets.
While old wiring, even that which uses knobs and tubes, is not inherently dangerous, abuse of the electrical system by overloading circuits and time work to deteriorate insulation. If someone installs light bulbs with a higher wattage than the rating of the fixture, the heat can melt the plastic wire coating. Replacing the bulb with the right size bulb does not undo the damage, and the wiring can endanger those in the home.
Some homes built in the 1960s and 1970s used aluminum wiring instead of copper. When aluminum wire joins to the copper of fixtures, it corrodes and the connections loosen. The loose connections increase resistance and create heat, causing a fire danger. Options include rewiring the home with copper or using special connectors anywhere copper and aluminum wires join.
Many older homes have a 60-amp service panel. It does not provide adequate power for central air conditioning. If the home has a small service panel or older style fuse box, consider upgrading the wiring and using a minimum of a 200-amp panel.