In the past, monitoring your home’s energy usage meant waiting for the monthly bill to arrive in the mail. Now, with the Aeotec Z-Wave Home Energy Monitor (HEM) you can monitor your energy usage in real-time. You can even monitor your energy usage from your smart phone. That energy usage information can be put to work and can even save you money:
- If you are on a tiered plan with the electric company, and you pay a penalty if your usage goes over a certain limit, you can use the data from the Home Energy Monitor to trigger an alarm when your usage approaches the limit. Your home automation system can also use that energy information to trigger an event that automatically turns off electrical equipment such as HVAC, water heaters, and networked clothes dryers in order to avoid exceeding the limit.
- If you are trying to identify energy wasters in your home, you can watch the energy usage in real-time as you unplug appliances. You would get a lot of exercise trying to do this by running out to the power company’s meter. Now you can just bring up the live data on your phone or tablet. The HEM reports instantaneous Wattage; you don’t have to wait for the power company’s meter to tick off the next kilowatt-hour.
- If you are making energy-saving changes to your home, such as installing more efficient HVAC, adding more insulation, or upgrading your windows, you can get immediate feedback on the effects of those changes.
- If you have a grid-tied solar system, you can have the satisfaction of watching the HEM display a negative value when you are selling excess power back to the power company.
- You can program you home automation system to sound an alarm when the clothes dryer is done.
- You can use the Home Energy Monitor to confirm that the electrical loads on the two AC phases coming into your home are properly balanced. (Best practice dictates that heavy electrical loads such as the stove, dryer, water heater, HVAC, and pool are evenly distributed across both electrical phases or legs.)
- You can verify the accuracy of your power bill.
The Aeotec Home Energy Monitor comes with two “Amp clamps” that will attach to the two phases of the main power line coming into your home. The connection will be made at the main circuit breaker panel, immediately upstream from the circuit breakers.
Whether the breaker panel is located indoors or outdoors, you will need a licensed electrician to install the Amp clamps. In most cases the cover of the breaker panel will have to be removed, exposing all kinds of energized surfaces. If you don’t know what you are doing, or if you get distracted while that cover is off, there is a real possibility that somebody could get electrocuted.
Before removing the cover of the breaker panel, your electrician will have to shut off the power to your home at the main disconnect, located outside at the power meter. Be sure to shut down all of your sensitive electronics and computers before shutting off the power to the house. Your electrician should place a lock on that electrical disconnect to prevent anyone from restoring the power while he or she is working in the breaker panel.
After opening the circuit breaker panel, your electrician will clip the Amp clamps of the Aeon Labs Home Energy Monitor around the two “hot” wires of the main cable bundle coming into the box.
Each of those two incoming wires is one phase or leg of the two phases coming into your home. In the U.S., each of those phases measures 120 Volts of alternating current (AC) with respect to the neutral or common leg, which is the white cable in the middle of my breaker panel. 120 Volts is dangerous enough, but there is a 240-Volt potential from one hot leg to the other (the black cables). Again, a licensed electrician with knowledge and understanding of electrical systems and electrical safety should complete the electrical installation inside the main circuit box.
You may have noticed that the circuit breaker panel is entirely enclosed in metal. This metal enclosure would block or severely diminish the Z-Wave radio signal if you were to mount the HEM inside the box. Fortunately, the wire leads from the Amp clamps are long enough to extend through one of the knockouts in the box, allowing the HEM to be mounted outside of the box. The HEM comes with a mounting bracket that would allow you to mount it to the wall or to a wall stud.
In my case, the wall that my breaker panel is mounted on is unfinished, making it easy to mount the HEM outside of the breaker panel. If your breaker panel is on a finished wall, it may be a challenge to mount the HEM outside of the box. Perhaps the HEM’s Z-Wave signal would be strong enough to get through the box if you had another Z-Wave device located near enough to act as a repeater or signal-booster.
The Home Energy Monitor comes with an AC adapter for powering the device through its USB port (the USB port can also be used to update the HEM’s firmware using the included adapter cable). The HEM can also be powered by four internal AA batteries. However, these batteries should be considered as backup power, because the Home Energy Monitor likes to send a lot of messages and could quickly drain the batteries.
If you do not have an AC outlet nearby for powering the HEM, you might ask your electrician to mount the HEM’s AC adapter inside the breaker panel, possibly by installing an electrical outlet inside the panel, and then passing the HEM’s USB cable through the same knockout that you used for the Amp clamp leads.
Connecting the Amp clamp leads to the Home Energy Monitor was a bit of a hassle. The plastic threads tended to bind or become cross-threaded. A bit of Teflon tape on the threads may have helped.
The HEM is designed to be weather tight to IP43 standards when mounted upright with the wires protruding from the bottom of the unit. This enables it to be mounted outdoors, if that is where your breaker panel is located.
Inclusion into a Z-Wave network is accomplished by pressing the black button that is located just below the batteries. If the Aeon Labs Home Energy Monitor was not successfully included into the Z-Wave network, an internal LED will blink after you press the button. If the HEM was successfully included into the Z-Wave network, the LED will be lit solid after pressing the button.
After including the Home Energy Monitor into my Homeseer system I could see that the HEM was sending instantaneous Wattage readings from each of the two legs every 10 seconds, and that the accumulated values for kilowatt-hours were being updated every two minutes:
The update intervals and thresholds for these readings can be modified through the HEM’s parameter settings.
I was curious about the accuracy of the HEM versus the power company’s meter. While watching the power company’s meter outside, I waited for the kilowatt-hours to tick to the next number, and then I immediately reset the HEM’s accumulated values displayed on my tablet. Then I went inside and started some laundry. I noticed after starting the clothes dryer that the instantaneous Wattage on both legs jumped up. This is an indication that my clothes dryer uses 2-phase AC, or 240 Volts.
When the two legs of the HEM displayed a combined KW Hours of 0.900, I ran outside to watch the power company’s meter but discovered that it had already ticked to the next number. I thought that maybe the power company’s meter was ticking 10-percent faster than my actual usage.
Remembering my electronics training, I knew that to calculate Watts, you have to know the line Voltage and the current. The Amp clamps provide the current reading, but the HEM does not have any electrical connections for measuring the line Voltage. I wondered if the 10-percent error was due to the Home Energy Monitor not knowing my Voltage. It turns out there’s an HEM parameter for selecting line Voltage, and you can set it to 120 VAC or 240 VAC. Mine was set to “unknown.” In my opinion, the HEM’s line Voltage setting should not default to “unknown.” After setting parameter 1 to 120 VAC, I went back and watched the meter, and on the next try it rolled over exactly when the HEM indicated 1 KW.
No mention of the line Voltage setting appears in the consumer-level documentation that came with the HEM. Advanced documentation for the Home Energy Monitor, including documentation on the line Voltage parameter could not be found at the Aeotec site either, but it is available at the website for the Pepper1 Z-Wave certification labs in Europe: advanced functions for developers
After doing the laundry, I did some poking around on my Homeseer pages and found that Homeseer had automatically started graphing my power usage. This is proof that I was actually doing laundry for four hours on my day off, and not just sitting around:
Adding an Aeotec Z-Wave Home Energy Monitor to my home automation system has been fun and educational. It has been educational to see my energy usage patterns and to see which appliances use the most energy. It is also educational to see in action the electrical concepts of Amps, Volts, and Watts. It is fun thinking of the various automation events that I will be able to trigger using my energy usage information. The ability to monitor my energy usage may even help me to lower my power bill. The Home Energy Monitor itself is so inexpensive compared to the potential energy savings that it makes sense to install one. However, the installation of the Home Energy Monitor is probably beyond the capabilities of most home owners, and should be left to a trained professional.