Measuring your home’s energy consumption is the first step toward finding ways to decrease it. While almost every residence has an electric meter, it usually only shows total household energy (kWh) consumed, although some include instantaneous power being used (kW). And the meter is usually placed where it is convenient for the utility—not for you—to read. But conservation-minded homeowners and renters can choose from several products that measure and record electricity consumption to reveal the energy hogs. The information is shown on a convenient countertop display or remotely on a smartphone or a computer screen.
If you want to use energy data to help reduce usage or convince other household members to adopt energy-saving behaviors, an energy monitoring system is for you. Or maybe you want to see how large a backup generator you need for utility outages, or how large a solar-electric system you need for your home. Maybe you just want to identify the biggest electricity loads in your household. If you already have a PV or wind system, you might need to monitor the on-site generation.
A typical home energy monitoring system includes sensors, a data gateway, and a display to receive and view the information. Standard information includes energy consumption in kilowatt-hours (kWh) and power draw in kilowatts (kW). Often, monitors include the cost of the electricity consumed, and some allow programming with time-of-use rates.
Monitors require sensors at each point of measurement. Current transducers (CTs) and pulse sensors are most common. CTs are available in split-core or solid-core varieties. Split-core CTs make it easier to install in existing electrical installations, since you can open up the “donut,” and then close it around the wire. Note that CTs are typically not interchangeable between different systems.
A magnetic field is created as the current in the wire flows. When that magnetic field moves through the coil of the CT, it generates voltage proportional to the current flow. This voltage is measured by the electronics and converted into an amperage reading. At the same time, the voltage in the circuit is measured directly, and simple multiplication results in kW. Include the elapsed time, and kWh are computed. The other sensor type—pulse—counts the electronic pulses made by the utility meter as it counts units. Many utility meters for electricity, gas, and water are pulse meters. Simple pulse sensors are not sophisticated enough to determine whether the energy flow is incoming from consumption or outgoing from a home source, like a PV system.
Some meters gather more data from the sensors than others, updating readings every second compared to every 30 seconds. The way in which the data is used in calculating kWh or instantaneous kW will also influence the meter’s accuracy.
The sensors are hard-wired or communicate wirelessly through data loggers or transmitters that, in turn, send data to a local display. Some systems do not need or do not use a separate display. These transmitters are connected to the router so they can communicate within a local area network (LAN) and/or through third-party servers over the Internet. Several transmitters and gateways require a power supply and consume from 3 to 10 W. Most monitors allow information to be downloaded into a spreadsheet for further analysis.
Powerhouse Dynamics’ eMonitor uses CTs and a base unit installed in the electrical panel to collect data. The base unit communicates with the eMonitor Gateway, which in turn sends the data to off-site third-party servers over the home’s broadband connection. Users can view real-time usage information from up to 42 circuits wherever there is an Internet connection.
The basic model, the eMonitor 4-14, comes with the equipment to monitor total building electricity consumption, as well as usage in 12 additional circuits. The eMonitor 4-24 and 4-44 can handle 22 and 42 total circuits with the addition of expansion pods, additional CTs, and additional monitoring services. In all units, two of the circuits are reserved for monitoring the main electrical service entering the building.
The base unit needs a 15 A dedicated circuit, though these products consume only 3 to 10 W to operate. In addition to the installation of the base unit, CTs, and the communication gateway, setup requires inputting circuit descriptions via a computer connection. Further configuration and registration allow the opportunity to confirm that communication is operating as intended and that all circuit labels were input correctly.
There is no local display. To view data and graphs, an Internet connection is required. The base unit will store data for several days in the event of loss of connectivity to the host server.
The eMonitor also offers remote control of compatible, Wi-Fi supported, third-party thermostats. If you forgot to turn the air-conditioning off before you left home, you can do this with a smartphone app—from anywhere. In the works is a plug-load-level control device that will allow remote-control of various appliances, such as a computer or window unit air conditioner.
The eMonitor offers some unique features. User-programmable alerts can help inform you about potentially worrisome conditions, such as a sump pump failure. These messages can be sent by email or text message to your smartphone. Apps for the iPhone and iPad allow viewing real-time operation and interface with the control features. The number of circuits that can be monitored makes the eMonitor appropriate for large homes and small businesses.
The eMonitor 4 is available through a dealer network or online retailers. A two-year monitoring service contract is required.
Like the eMonitor, the eGauge has the ability to monitor multiple circuits. However, the eGauge monitor does not require a data monitoring contract. The information resides locally, rather than remotely on an outside web server.
The CTs are installed inside the electrical panel where the monitored circuits originate, so some electrical skills are needed to safely install it. The eGauge main unit, which also resides in the electrical panel or immediately adjacent to it, can accommodate input from up to 12 CTs. The main unit needs a 240 VAC, 15 A power supply which is supplied from within the panel being monitored. To view the data, the main unit is connected to your local network and computer, via Ethernet cable, or a HomePlug accessory or another variety of Wi-Fi adapter. While the eGauge data lives locally, it also can be viewed online. The eGauge doesn’t offer a smartphone app, but its data screen can be viewed with any web browser.
The eGauge does not include control features. The setup and monitoring interface are touted as intuitive and straightforward.
Current Cost’s EnviR monitor basic model will monitor the consumption on one 240 VAC circuit—typically, the two incoming service wires. Setup of the standard kit includes installing a set of CTs and the battery-operated transmitter, which wirelessly transmits to the display, if within 100 feet.
Current Cost offers accessories to monitor more circuits, view information online, and track usage of single appliances. For online viewing, you can opt for the Enerati Gateway kit, which requires a data subscription. Individual appliance monitors (IAMs) are plug-based sensors that monitor electricity usage of individual 120 VAC appliances, recording real‑time power and energy use at 8- to 10-second intervals. Each display can accommodate up to 10 transmitters. Monitoring packages are also available for renewable energy systems that can track consumption, RE-system generation, and net usage. The EnviR can be purchased directly through the website or through resellers.
Locus Energy initially designed the LGate products to serve sites with PV systems. Now, it offers low-cost revenue-grade metering with the LGate 101. The LGate 50 monitors a building’s electricity consumption in kWh, as well as power in kW. The LGate meters also come with a five-year monitoring contract (included in the purchase of the unit) that can be extended for another five years.
The LGate uses CTs installed in the electrical panel. The LGate itself is installed outside the panel, but nearby. It accepts up to two sets of CT inputs, which are generally used to measure total building energy consumption and PV production. The meter requires its own 120 VAC, 15 A breaker and corresponding wiring. The LGate 101 requires a 240 VAC, 15 A power supply. The LGate connects to the Locus Energy servers through your Internet connection brought directly to the meter. LEDs inside the meter box indicate its communication status.
The LGate meters do not come with a display. Data is viewed via the SolarOS platform through a browser. The information is downloadable. LGate products are available only through solar contractors.
The OWL devices are designed to monitor only one circuit, usually the incoming wires to the main electrical panel. The CTs require accessing the main electrical panel for installation. The CTs are connected to a sending device, placed just outside the panel, which wirelessly transmits data to the remote display, which can be located up to 90 feet away. The OWL devices show instantaneous power usage, energy consumption, and cost. Both the display and the sending unit are battery-operated. The products have a longer history in the UK and Europe, but these limited versions are now available in North America through the OWL partners and other online retailers. The OWL Intuition series (which may not yet be available in North America) allows users to view information via any Internet-connected computer or by using a smartphone via the OWL app. A PV version monitors on-site PV system generation along with utility consumption.
Blue Line Innovations’ PowerCost Monitor can be installed by homeowners—an electrician is not required—since the sensing unit attaches to the outside of the electric meter. The base model includes the sensor and display.
A pulse sensor on the meter communicates wirelessly, using your home Wi-Fi, to the display unit. For the basic BLI-28000, the information is only viewable on the display provided. To view your household’s real-time electricity usage online or to store and analyze data over time, you’ll need to choose from one of the third-party software offerings and need the PowerCost’s Wi-Fi bridge or gateway. These Wi-Fi accessories require a 120 VAC power supply, while the sensor units and displays operate on batteries.
The sensor unit may not be compatible with your electric meter—check compatibility on the Blue Line website before purchasing. The base unit will keep a cumulative total, as well as show real-time, instantaneous demand. The user programs in the utility rates so that the display can report the cost of electricity consumed. Alone, the PowerCost does not offer any control features, but some models can be synced with the Iris automated control system, enabling you to incorporate usage information into a home automation platform.
Energy Inc.’s basic TED 5000, will monitor total household electricity consumption and show it on a small display. On the display, you can toggle through instantaneous power (kW), cost per hour, recent use, monthly use to-date, and you can compare to a monthly projection.
TED uses one or more measuring transmitting units (MTUs) for each set of CTs, and up to four circuits can be monitored. The MTU resides in the electrical panel being monitored and requires a 120 VAC power supply. The MTU transmits a signal over the household wiring to the gateway and/or the display. If you prefer to view graphical information on a computer screen, you can forgo the display. Setup requires downloading Energy Inc.’s proprietary Footprints software and configuring your gateway much like another device on your network. For online viewing and smartphones, several third-party applications exist.
TED can monitor on-site renewable energy generation as one of its data inputs. While not revenue-grade monitoring, it may be sufficient for keeping informal tabs on your electricity consumed and generated.
Installers report that it is not unusual to spend time troubleshooting the signal over the power line, since other electronic devices in the home can interfere with TED’s signal. TED can be purchased from the website directly, or through distribution channels.
Wattvision is easy to install, but it only measures total electricity consumption—not other circuits or RE-system generation. With a pulse sensor installed at the electric meter, it does not require an electrician to install. You just select the correct sensor based on your existing utility meter technology, brand, and layout. The sensor is connected via 50 feet of wire to a Wi-Fi gateway, which requires a 120 VAC receptacle.
No display comes with the unit—the real-time data is viewed via computer or smartphone. Data can be downloaded to Excel or other data management software for further analysis.
One unique twist on Wattvision’s approach to energy monitoring is the ability to “share and compare” your use with the electricity consumption of other Wattvision users. This has the opportunity to encourage engagement about energy consumption. The Wattvision unit is available on the company’s website.
Although it falls outside of the scope of single-residence monitoring, one group of products in particular is worth mentioning—The E-Mon D-Mon (emon.com), which has been a workhorse of the electrical monitoring industry. The E-Mon products are targeted at commercial, industrial, multi-tenant facilities. Many electricians are familiar with these robust revenue-grade metering products, which start at $400.
But for monitoring a single source, the Blueline, OWL, or Wattvision products are good candidates. For monitoring a few circuits with some optional features, the EnviR and TED will probably do the trick. With more rigorous monitoring requirements, the eGauge, eMonitor, or LGate are the meters worth considering.
Erika Weliczko lives in Cleveland, Ohio, where she operates REpower Solutions. Erika is a licensed electrical contractor, and is a NABCEP Certified Solar PV and Small Wind Installer.