WHAT GOOD IS A 100 AMP ELECTRIC SERVICE?
Will your home inspector tell you if your electric service is too small?
Electric service started in the 1920s - gas light chandeliers were converted. Knob and tube was run. 30 amp 110v was a very common size. In the 1950s, the average new home was equipped with a 60 amp electrical service connected to a screw-in fuse panel with two fuse blocks. The common distribution was a fuse block for the stove and one for the hot water tank. The balance of the homes electrical needs were served by six, 15amp screw-in fuses.
Starting around 1965, the average new home was equipped with a 100 amp electrical service and some of them used the latest in technology, circuit breakers.
Now the average home is equipped with a 200 amp electrical service with a distribution panel handling up to 40 circuit breakers serving the electrical needs of the home.
Old style distribution panels, those with screw-in fuses are generally considered fire hazards. The contact between the base of the fuse and the buss bar oxidizes or charcoals from poor contact. In order for the current to continue to flow heat is generated. In many areas, insurance companies will not renew homeowner insurance if the home is equipped with an electrical distribution panel that has screw-in fuses.
The real issue is always adequate power distribution at the points of use.
If we do the load calcs, flats can be served by 60a and small houses by 100a as long as the appliances are gas. This results in a safe and compliant installation.
While it goes beyond the scope of a home inspection to perform load calculations, occasionally I’ll do a rough calculation if I get concerned that an electric service is too small for a house.
At nearly every inspection, I find one of two things: either the electric service is outdated and obviously too small, such as the 30 amp service pictured here, or the service has been upgraded or over-sized and is plenty large enough for the home. I don’t find much in-between those two.
plug in a few numbers at an online load calculator -
the smallest allowable service for a new home today is 100 amps.
For a condo or flat its 60a
