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
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.
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.