Review: Powerhouse Dynamics eMonitor
This new energy-saving monitor provides a detailed look at your electricity use.
October 15, 2010 by Steven Castle

The coffee maker uses almost 900 watts when it’s brewing? And what’s this 1,100 watts in the rear bedroom and bath and another 1,200 in the kitchen plugs at 6:24 a.m.?

Such are the travails of a homeowner with an energy monitor—or specifically, the new eMonitor from Powerhouse Dynamics. The eMonitor measures a home’s electricity use at the circuit level and provides a web-based interface for seeing both your home’s total electricity draw and that at the circuit level. This means the electricity use of major appliances like the refrigerator, electric clothes dryer, electric stovetop and oven are easily measured and identifiable. Other circuits, like “rear bedroom and bath” and “kitchen plugs” require a bit of detective work.

Come to find out, the 1,200 watts on the kitchen plugs is a toaster/convection oven, and the 1,100 watts in the bath is a hair dryer.

In my two weeks with an eMonitor, I’ve also uncovered the cycle times of our two refrigerators. I’ve found that the old fridge in the garage uses about 50 watts more when cycling on than the new one in the kitchen, an aging dehumidifier in the basement uses 800 watts when it’s on, and our old electric dryer uses more than 5,000 watts when it’s on (yikes!).

Since getting the eMonitor, I occasionally become absorbed in examining our electricity use and seeing where we can save. The front page of the secure site shows my home’s current electricity usage in watts (updated every minute), the circuits and appliances currently drawing the most power, the top energy users in our house over the last few days, our monthly electricity costs to date (you input your utility’s rates during the registration), and a pie chart representation of our top electricity users. There’s also a carbon footprint comparison—ours is still smaller than our state’s average—and a graph of our electricity consumption over the past two days.

You can dig deeper and see a color-coded graph of hour-by-hour or minute-by-minute usage of all your circuits. You can even highlight a section to get more granular.

You can also go to a Circuits page to examine individual circuits, and some of these come with energy-saving suggestions, like reminders to clean the lint filter in our electric dryer.

My only complaints include the color-coded circuits graph showing energy usage in watt hours (watts divided by hours of usage), while the more detailed circuit-level graphs show usage in watts. This was initially confusing, and I thought something was wrong with the interface. (Though the watt hours have come in handy when calculating the Energy Factor of my older appliances, to compare with newer Energy Star-certified models.) Also, as part of a subscription to its service, Powerhouse Dynamics sends alerts when circuits appear to be off or using abnormal amounts of energy. I keep getting alerts for my boiler and well pump being off, though while registering I made sure to give ample time for these to be “off.” I love the idea of alerting homeowners to appliances like water heaters that are using too much energy and may be about to fail, but the alert system appears to require some finessing.

All in all, the eMonitor works well and is a useful tool for identifying unnecessary power draws in a home. I can’t imagine trying to do that with a system that only measures a home’s total electricity use.

Steve’s Report Card
From the early results of my eMonitor, it looks like my family should look into:
-A more efficient electric clothes dryer.
-A more energy-efficient dishwasher.
-A new, Energy Star-certified dehumidifier.
-More dimmable lights, CFLs and LED lamps.
-Further reduction of unnecessary standby/vampire loads.

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Steven Castle - Contributing Writer
Steven Castle is Electronic House's managing editor. he has been writing about consumer electronics, homes and energy efficiency topics for two decades. He is also the co-founder of GreenTech Advocates.

At a Glance
-$699 for 24 sensors plus $249 two-year subscription
-$499 for 12 sensors plus $189 two-year subscription

Circuit-level monitoring
Easy, intuitive interface
Relatively simple setup

Alert system needs work
Watt hours vs. watts can be confusing

How it Works
The eMonitor measures electricity usage via circuit transformers (CTs) that clamp around the two electric “mains” and up to 24 circuit wires. These sensors measure the electromagnetic field created by electricity use, and are fairly accurate. The CTs connect to a processor mounted near your main circuit panel and then attach via Ethernet to a network router and home network. This enables Powerhouse Dynamics to see the measurements and include them in the computer interface.
You also have to fill out a form on Powerhouse Dynamics’ registration site so that it knows what circuits are what. The electrician who installed my system would have liked numbers on each CT for easier marking, and a processor capable of handling more circuits. (I had to leave out two bedrooms, and my house isn’t big.)

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