The electric meter is normally part of the service entrance equipment. It is there to measure the amount of power used on the property. Some properties may have more than one meter, maybe due to multiple occupancy or discounted power for heating use.
As the meter is a rated component like any other, the ampacity of the meter and its base cannot be lower than the stated total available amperage. We will look at this further in the next section.
Meter Bases
As meters have increased in capacity over the years, the meter bases have changed. The very earliest meters (as pictured at the right) had no separate base, and are typically rated for only 30-amp supply.
Round meter bases: Common from the 1920s up to the 1950s, they were rated for only 60 amps and are still often seen on older properties.
Square meter bases: Typically found on homes from the 1950s to 1970s, these are still used in some smaller housing units, such as apartments, and were only rated for 100-125 amps.
Rectangular meter bases: are the current minimum on single-family homes. These are rated for 200 amps and typically bear the marking "200CL."
Understanding meter bases is an important part of being able to properly evaluate the maximum available amperage in the home, but should not be relied on completely when sizing a service.