Cost of updating electrical
In some states, you will be required by law to upgrade your switchboard when you have air conditioning installed.As a rule of thumb, seriously consider replacing your switchboard when you add any high-energy consuming new appliances to your home.To do that, testing and perhaps other modifications will be required.
Circuit breakers can be reset after they trip, which is a huge advantage over fuses, but they don’t add any level of safety. Compared to the minimum number of circuits required today, this is totally insufficient.
Low-efficiency models will cost less, but result in higher energy bills.
High-efficiency models cost more, but save more over the long haul.
For one thing, just from a purely legal perspective, it's usually a violation of the electrical code.
Having knob and tube wiring can cause problems with home sales, insurance paperwork, and other activities related to your home.