I have run in to 2 deals so far this year that the electrical has been an issue in the sale.  There is more information needed for our industry.  Both homes had aluminum wiring and both homes (we were told) required an ESA Certificate.  The first home had an expensive time of it as the inspection created more issues that needed to be fixed prior to certification.   The other realtor in the sale got stuck with paying for the certificate and the inspection by a master electrician.  The other home was pretty much o.k.  The certificate itself cost just over $100.00.

I want every house I sell to be safe .... however, I am not an electrician.  If the walls and ceiling are finished in the basement, how am I to know (without taking off the elctrical panel - which I cant do) that a house has aluminum wiring ..... That is the question that is costing us and our clients money right now.  The insurance companies .... State Farm and Co-operators, Pilot and more are asking for an ESA Certificate or at the very least a Master Electrican to put his neck on the line and certify that a house does NOT have any electrical issues....good luck with that one, before they will insure a property.......  Who should pay????

More and more frequently insurance companies are refusing to insure homes with 60 amp services, knob and tube wiring, and in some cases, even aluminum wiring. Like all electrical components, they can be dangerous is they do not meet certain minimum requirements, but they can also be as safe as any others.
The Consumer Division of the Insurance Bureau of Canada operates an information line at 1-800-387-2880 that can answer some questions with respect to how to obtain insurance on homes equipped with 60 amp services, knob & tube and aluminum wiring. You may also be requested to get an Electrical Safety Association Certificate (www.esasafe.ca) for clearance if you are selling or buying a home with potential electrical issues.
Most standard sized homes built prior to the 1960's were equipped with a 60 amp electrical service. This size of service was reasonably well suited to the needs of living at the time. However, the search for convenience and enhanced lifestyle has generally increased the demand on the electrical systems of homes today.
A common misunderstanding is that the ampacity (size, or capacity) of a home's electrical service is determined by checking the main breaker or fuses or the rating imprinted on the panel. This method of determining size is fraught with problems as the ratings of breakers, fuses and panels may correlate to the size of the electrical service, but in many cases they don't. The panel could have been upgraded without upgrading the service wires.
The size of an electrical service is established by the ampacity (capacity) of the incoming service wires. The only reliable method of determining the size of the service is to observe and correctly identify the size of the incoming wires and the related equipment (mast, meter base, etc.).

A 60 amp service will, limit the number of appliances that can be used at any one time. For safey and practical purposes the adequacy of an electrical service should be judged against the size of the potential or expected load it will be required to carry. One indication of a service that is undersized for the demands applied to it is the blowing or popping of the main fuses or breaker switch. If the service is undersized for the current demands, increasing the size of the service is one option.
KNOB AND TUBE wiring is a type of wiring which was in common use until the 1940's and sometimes used as late as the 1950's. The nick-name is derived from the ceramic knobs that are employed to insulate and secure the wiring runs and the ceramic tubes employed to protect the wires where they pass thru potentially abrasive materials (primarily wood joists, studs etc.) Unlike subsequent wiring systems where all the wires in a run are enclosed in a cable, the two wires (black/hot and white/neutral) run separately and only come together at a terminal (switch, receptacle, fixture, junction box etc.).
Knob & tube wiring does not provide a third wire for grounding and is therefore considered unsafe in kitchens, bathrooms, laundry rooms and outdoors. In other areas, knob & tube wiring that is in good condition with sheathing intact, properly protected from damage, and that hasn't been subjected to extended periods of overloading which can cause it to become brittle, should not pose an increased safety risk.
Aside from the preceding concerns, the primary risk with knob & tube wiring, it seems, is it's relative accessibility for amateur repairs, upgrades and maintenance. It is not uncommon to see a system with knob & tube wiring that has a history of amateur work (poorly joined connections, unfastened runs, unprotected wires, etc.). If a house does have knob & tube wiring wiring it should be inspected to ensure that it is properly installed and in good condition.
Note: Many older homes with originally installed knob & tube wiring have had some of the wiring upgraded. While modern wiring is visible in many areas, much of the knob & tube wiring may still be in place and concealed beneath floors, above ceilings and hehind walls.
If a few, but not all, of the circuits are in poor condition they can be replaced eventually without rewiring the whole house. However, if most or all of the circuits are in poor condition, it may be more economical to completely rewire the home. Rewiring can also allow the electrical system to be more convenient as the new circuits can be designed to accomodate the present lifestyle of the occupants of the home.