Many houses built in the last century were constructed with minimal electrical service. When looking back to those times, there simply weren’t that many electrical devices in a home. Air conditioners weren’t readily available until after World War II, and in 1955 only 10 percent of U.S. households had electric clothes dryers. Hair dryers, toaster ovens, electric ranges, microwaves, electric water heaters and other such things were added over the years, greatly increasing electrical demands.

With few of today’s modern conveniences, a house could easily get by with only 50-60 Amps of electrical service, and even today this level of service does not pose a problem, as long as electrical devices are kept to a minimum. However, when homeowners with such basic service start adding modern appliances, they quickly run out of electrical capacity, which can result in local brownouts, blown breakers or fuses, or overheating of wires and a possible fire hazard.

Computers don’t take much, but they don’t like brownouts or flickers in power. For any type of computer or computerized appliance, it’s a good idea to use surge suppressors and uninterruptible power supplies to prevent damage. This includes computerized sewing machines, exercise equipment, TVs, digital video recorders, and cable boxes.

Another consideration when with older homes is that many of the wires coming from the poles to the house, and then down the house to the meter, are 40-50 years old and are now frayed. Often the wire wrapped around the central conductors is now showing through. Contrary to common belief, that is not a ground, but a current-carrying conductor, often carrying substantial current. Although wrapping with tape is acceptable by some, most electricians agree that frayed Service Entrance (SE) cables should be replaced for safety. At a minimum, that wire needs to be replaced so that it is safe and it is a good opportunity to UPGRADE the entire service to a more modern 150-200A service. Most municipalities won’t install less than 125-150A, and most times 200A service is the same price as the lower, so 200A is installed. Even Townhouses and condominiums now are provided with 125-150A service per unit.

Some all-electric homes, or homes with lots and lots of circuits, may even need a larger service (400A) because of the requirement for no more than 42 circuits per panel, and 150-200A per panel. With the new rules, the number of circuits per panel is being relaxed, but homes with multiple air conditioners, water heaters, second kitchens, clothes dryers, guest quarters and other large users of electricity may still need the larger electrical service.

How to Tell the Amperage

  • Round-Base: 50 to 60 amps
  • Small Square Base (sides equal the diameter of the meter): 50-60 amps
  • Large Rectangular Box (approx. three times the diameter of the meter): 150 to 200 amps
  • Extra-Large Box (height approx. six times the diameter of the meter): 400 amps

Modern Life Consumes Electricity

Here are typical amperage requirements for some common household appliances.

  • Electric Range: 40A
  • Wall Oven: 40A
  • Modern Electric Clothes Dyer: 30A (min.)
  • Air Conditioner, outside unit: 25A (min.)
  • Air Conditioner, inside unit: 15A
  • Microwave: 12A
  • Toaster: 12A
  • Hair Dryer: 12A
  • Dishwasher: 15A

To calculate how many amps an appliance needs, divide the wattage by 120 (normal household voltage). For example, a microwave oven that uses 1800 watts needs a 15 amp circuit. (Amps = Watts/Volts)

Safety Note

The service entry cable should always be protected from the elements, and from the possibility of abrasion or fraying. Soil settling around the foundation of a house can pull the cable conduit away from the meter box, with potentially disastrous consequences.

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