The eMonitor

I have a new toy. It's a totally geeky toy - almost everyone else would rather have a large plasma screen TV. It's called eMonitor and it is made by Powerhouse Dynamics. You can buy one from folks at Powerwise Systems or Energy Circle. It's a device that measures energy usage in your house circuit by circuit, and uploads that info to a web site where it can be viewed in a number of ways. Any circuit being measured has a current transformer (CT) (or sometimes two, for some 240V loads), and you can get versions with 14 CTs, or ultimately as many as you want. I chose one that does 24 CTs. That doesn't get every circuit - I have some left over in what is called Unmonitored Power, maybe 3% of the usage. If I'm really curious I can always move some CTs from one circuit to another.

It's a costly doodad.  Mine lists for $695. Plus, you pay for access to the web site to see the data. In my case, I paid $240 for two years of monitoring access, plus an additional $108 to include my solar electric system (PV) in the mix. I installed the system myself, but they (or their lawyers) recommend that it be installed by a licensed electrician. It took a couple of hours to put it in and then enter the circuits on the web site, so it's clear what each circuit being monitored is feeding. If your electric panel has been poorly or inaccurately labeled (the norm in my experience) count on a couple of hours, preferably with another person, to track down what is on each circuit breaker.

When you're done with the installation, the panel is pretty darn full of wires. The eMonitor has a component that stays inside the panel, that the CTs connect to, and it communicates wirelessly to the unit outside of the panel that connects to the modem and thereby the outside world.

When I go to the Sitesage web site (recent, very unfortunate name change :-), this is what I see:

The top of the page shows how much power the house is using, how much is being produced by the PVs, and what the net power draw or export is. It also shows the largest power users. In the snapshot above, you can see that the heat pump water heater (HPWH) is running, the Fujitsu minisplit heat pump is on at a very low level (outdoor temperature of 48F is shown - they must get that from another web site, there aren't temperature sensors connected to the eMonitor, although Powerwise can fix you up with all kinds of sensors too), the unmonitored power is 65W (my Macbook Pro, actually, as I write), and the heat recovery ventilator (HRV). There are other tabs for more information, or to set alerts, etc.

Next on the page is a donut chart showing energy usage over the past 30 days. It's been wintry, so the minisplit has been the dominant user. I'm not sure what the horizontal bar graph in the upper right corner is measuring.

Here I can see total usage vs. production for various periods - either by month for a year, or by day for a month. Average outdoor temperature, and heating and cooling degree days are shown as well. On the right, the actual energy usage pattern can be viewed for various durations.

The button entitled Export Data allows you to to export data by minute, day, or month into an Excel spreadsheet - very nifty.

There's a lot more to say, about looking circuit by circuit, setting alerts, and how this is useful. More in another post.

 

 

 

Comments

[David Fay]

MR: "I'm not sure what the horizontal bar graph in the upper right corner is measuring."

You've probably figured this out by now, but it looks to me like the bar graph is showing net usage by month (i.e., usage minus production). If so, the label on the graph is misleading.

[Marc Rosenbaum]

David, you're right, it's net - thanks!