Working for a safe, affordable, vibrant, innovative, and interconnected city.
Learn More
Seattle.gov Home Page
Seattle.gov This Department
ADVANCED METERING AND ELECTRICAL SAFETY
The Basics of Electrical Service.

The wires that serve your home belong to City Light. The place where your wires connect to our wires is called the "point of termination". If you have overhead service, the point of termination is at the weatherhead (the pipe with the curved head that comes out of the top of your meter base, and is either mounted to an exterior wall, or pops up through your roof). If you have underground service, the point of termination is in the meter base. The weatherhead and meter base belong to the customer, and City Light owns the meter.

The meter base has a socket that the meter plugs into. Most residential sockets consist of four "jaws": Two on the "line" side (the wires that connect to the grid) and two on the "load" side (the wires that go to your breaker panel). The "line" side is always the upper set of jaws, and the "load" side is the lower set of jaws. Each side of the jaws is 110 volts. The two sides together are 220 volts, which is used for such appliances as electric water heaters and ranges.


Over time, meter bases experience wear and tear. Connections can become loose, and if there is consistent levels of high usage, meter bases can show signs of heat damage such as arcing or scorching. Occasionally, that wear and tear can cause service failure or - in extreme cases - fires.

You may have heard or read about instances at other utilities where advanced meters have been investigated for causing fires. In reality, what has happened has been that installers who have not been properly trained to recognize potential hazards have installed meters in places where repairs were needed prior to installation. Seattle City Light intends to make sure that all installers are trained to recognize such conditions and to not install meters until corrections have been made. In those instances, City Light will work with the homeowner to minimize any inconvenience or expense.

Advanced Metering Certification and Accuracy.

There's also a misconception out there about meters and UL listings. Traditionally, no meters - mechanical or otherwise - were evaluated by Underwriters Laboratory. Instead, they must meet ANSI (The American National Standards Institute) standards. Advanced Meters must also follow ANSI standards, but a few models have also attained UL certification.

All of City Light's Meters are certified as Class .2 Meters, per ANSI C12.20. That means that they have an accuracy of +/- 0.2% at time of installation. Since mechanical meters tend to slow down as they age, some of the older meters may have lost some of that accuracy and consequently are not recording all kilowatt hours consumed.

Advanced Metering and Residential Troubleshooting.

Advanced meters will collect customer kilowatt-hour usage information, just as today's meters do, and transmit that consumption information to City Light at scheduled intervals. They can also be programmed to detect instances where voltage or temperature at the meter base is abnormal and send an alert to our system control center for investigation. Early intervention when problems like this pop up can save property owners time and money in dealing with their electrical system.

Advanced Metering and Theft Detection.

When an advanced meter gets removed from its socket, it will send an alert to our metering department to investigate why this removal occurred. That can help curb current theft which is estimated to cost City Light over 3% of retail sales revenue per year. Since we are municipal utility, owned by the City of Seattle, this theft affects all of us.

Advanced Metering: The Building Blocks of the Smart Grid.

Advanced metering helps keep an eye on the health of the entire distribution system by noting things like overloaded transformers or distribution lines. This can help minimize outages and cut down on maintenance costs. It can also help us operate our distribution system more efficiently by giving us real time information on how much power a substation is distributing and how much power we need to have on reserve to maintain reliable service. Since we have a generation source that is 95% hydro-electric, this translates to much more efficient use of a precious natural resource - water. And it allows our low-impact hydro-electric projects to operate in an even more "fish-friendly" manner.

Reliable, low-cost electric power, delivered in a safe and environmentally-friendly manner. That's been City Light's goal throughout its 110 year existence. Advanced Metering will give us the 21st century tools to meet that goal.