Power Meter Installation

Installing a residential power meter requires one to work inside the main circuit breaker panel where electricity enters the home.  Turning off the main breaker cuts power to most but NOT ALL points within the panel.  Main feeders coming from the utility's meter to the main breaker always remain hot unless disconnected by the utility.

By all means, if you are not completely at ease working in this environment, call a licensed electrician to perform the installation.  Safety is of utmost importance!   If you are well aware of the risk, and accept the responsibility of working inside an electrical panel with hot spots, read on...

Most all power meter systems collect amperage date with current transformers or CT's.   These CT's are simply small coils that measure the inductance of the current flowing through the wire they surround.  Split core CT's look like small spring clamps that open and close with a squeeze to attach them to the wire.  Donut CT's are round, with no opening, and require the wire to be removed, inserted through the CT and then reconnected. Split core CT's MUST be used to measure power on the incoming feeders as these wires will remain hot through the installation and cannot be disconnected from the main breaker.   All other circuits to be measured can use either a split core or donut CT provided the conductors remain cold on the load side of the circuit breaker.  Donut CT's, being more compact and less expensive than split core CT's, are often used for individual circuit measurement.

Split Core CT's

Donut CT

Split Core CT's Installed on Mains

Notice the split core CT's clamped around the main feeder cables in the picture on the left.   The CT's should be attached around the insulated portion of the large black conductors. Use caution to avoid touching anything metal around the main breaker as the line or utility side remains HOT! When installing CT's it is a good practice to land the CT leads into the measurement unit or control module before clamping them around a live wire.

The reason for this is that the coil within the CT can generate an unchecked voltage if the leads are not grounded or landed properly.  Since amperage on the secondary side is very low the voltage is not lethal but mild arcing may occur.   No one likes to see sparks!

Voltage connections are generally wired through a dedicated, double-pole breaker. If you do not have room in the panel for an additional double-pole breaker, voltage leads can be connected to an existing 240 volt appliance circuit. Select the one with lowest use such as the range or clothes dryer as voltage readings may be affected slightly when the appliance is on.

Start your power meter installation by reading through the manufacturer's instructions carefully.   Gather the tools you will need and lay out the components to be installed near the main circuit breaker panel.   Remember to keep a flashlight handy since the power will be off during the installation.  Shut off power at the main breaker and remove the cover to the circuit breaker panel.

If your home has more than one incoming panel, such as with 400 amp service, individual CT's will need to be installed in each panel.  Do likewise if you want to monitor additional sub-panels or specific circuits.  Land the leads for the CT's in the measurement module before clamping them around a live wire.  If the conductor is cold, it doesn't matter.

Install a dedicated double-pole breaker and attach the voltage leads to the measurement unit or control module.  As a double safety measure, be sure the breaker is turned off before sliding it into the buss bar connector.  Use plastic tie wraps to tidy up the wiring and keep it routed away from any breakers or cover panel screw holes.  Reinstall the cover to the main panel, turn the main breaker back on and energize the new double-pole breaker for the power meter.

Assuming your system connects to a web server gateway using power line communications, simply plug the gateway or adapter module into an outlet that is served directly by the main panel.  A sub-panel outlet may or may not work depending upon the signal strength.  From the gateway or adapter run an Ethernet cable to your router or a USB cable directly to your computer depending upon the manufacturer's instructions.

If your power meter web server is local you should be able to open your browser, put in the system's IP address or name and see the set-up screen.  If the server is based remotely you may need to activate a subscription or set appropriate connections before seeing any data.  Follow software set-up instructions very carefully making sure all component ID's or serial numbers are entered properly.  Electrical data should appear immediately upon completion.

Cost information will appear after utility rate information has been entered into the system.  Use your latest electric bill to set this up.  If you cannot fill in all the rate information requested check your local utility's web site and search for rate schedules.  Download or print the rate information that applies to you and use it to complete the set up.

Some residential power meter systems will provide data about the size of your carbon footprint.   This is simply a ratio of the pounds of carbon to kilowatt-hours used.  Your actual carbon footprint will vary based upon the composition of generation sources, ie. coal, hydro, nuclear, natural gas and alternative energy.  Check with your local utility for a carbon footprint ratio that best represents their average generation mix and enter it into the system.

For more information on specific monitors please visit our Smart Meters page.   For software, visit Dashboards.  If you are still trying to get your arms around all the technology behind home energy monitors take a look at the Home Energy Monitor Systems page.

If you have developed a residential power meter system or know of one that is commercially available in the U.S. that is not listed on the Smart Meters page, please contact us if you would like to have it evaluated for inclusion on this site.