Product Reviews

Z-Wave and HomeSeer’s HS3 Control Software

Posted November 9, 2016

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.

Avoid Going Over Your Usage Limit

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.

Identify Energy Wasters

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.

Before removing the cover of the breaker panel, your electrician will have to shut off the power to your home at the main disconnect

The Accuracy of HEM

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.


Overall Strength

Ease of Installation



Quick Reference

Product Name
Home Energy Monitor

Aeon Labs


Rants and Raves

Matches the power company's meter for accuracy. Adjustable thresholds and notification intervals.

The consumer-level version of the documentation omits some essential information.


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