I recently received the below email from Lyn Chapman of Chapman Specialty Equipment & Inspection.  It seems that the Efergy E2 is made by a U.K. company and Lyn is based in Ontario, so I'm not sure how it would perform in the U.S., but it definitely looks like a good product has the potential to be a good product (see my update below for clarification).

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I was asked to conduct an independent evaluation of energy monitoring products for my company. I looked at numerous products and purchased the Black and Decker whole house Energy Monitor (which uses the same technology as the Energy Owl) , the TED 5000, and the Efergy E2. Here in Ontario we quickly found ourselves dead in the water with the Black & Decker unit as the majority of meters used by the various utilities are not compatible with the technology utilized for the device.

The TED 5000 is a good product but we found issues with the powerline communication system used with the devices. This required us to come up with solutions to make it work which included spending additional money on noise filters, installing dedicated breakers for the MTU's and locating the gateway close to the utility panel.  We then encountered the expense of running cable to the modem from the gateway location and this also limited the communication range of the remote monitor.  On the issue of the remote monitor, the first one sent to us was defective and would not work at all.  While the replacement monitor does work, it does not communicate everywhere in the building that we would like.  We were also unable to get the Google Earth feature to work.  TED support advised us that their Google Earth feature is not supported by all ISP's in Canada so we would have to sort that out with our individual ISP. In Ontario, the TED 5000 units have to be installed with a permit and then inspected by the Electrical Safety Authority, all at additional expense.  While we landed our TED 5000 with 4 pairs of Ct's and the remote monitor here for around $520.00,  by the time we had it installed and working,  we were over $1200. deep.

The Efergy E2 is also a good product and we found that it was capable of doing everything we needed including the collection of historical data and making graphs. The unit was quick and easy to  program, easy to install, and the wireless radio communication worked flawlessly. There was nothing else to buy, no permit to purchase, no electrical contractor to involve, just 30 minutes of my time and we were in business. We now have over 40 of the E2 units in service at our various client locations, all without a single glitch.  We have been purchasing our units from a company in Florida  at www.energymonitor.com

It is worthy of note that I was on a training course with Schneider Electric in Toronto a few months ago and an Engineer in the class from New York was expressing his concerns to me over the communication problems he had been experiencing with his Energy Detective. I told him about our experience with the Efergy.  After returning to the United States, he purchased and installed four E2's from Florida for his own use and that of his family. He has been absolutely delighted with the Efergy E2's he purchased.

I am advising you of this information as I believe that you would do your readers a great service by including the Efergy E2 in your product line up of energy monitors. These are difficult economic times and the Efergy E2 sells for about half the price of an Energy Detective. When it comes to monitoring energy, the E2 does a fantastic job.  I typically install an E2 in our client locations in less than 30 minutes including programming.  The Efergy E2 is also available for 3 phase installations.

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***Updated - 4/17/10 - I had a reader write me with the following comment: "I looked up the install info for the Elite and Elite 2 Efergy systems. They don't have a voltage connection and therefore do not sense voltage. Voltage is entered in the display. These are really current meters that don't measure kw or even volt X amps. The accuracy will be very bad with motor and transformer loads. Also inaccurate with voltage changes. The TED and also the ECM-1240 family (Brultech) are true kWh monitors."

And it seems that he is right.  I found the install instructions on Efergy's website here.  The instructions state:

STEP 1. VOLTAGE

Press and hold Mode Button for two seconds. Default voltage is set at 240V. Use BWD and FWD buttons to change the voltage. Press MODE Button to save your setting and move into currency selection setting.

And so if your voltage never varies, you will have accurate power consumption data, but if your voltage does vary....you have a problem.  How does the Efergy unit differentiate between 240 V loads and 120 V loads?  For example, most U.S. homes have both.  Your toaster or TV runs on 120 V, but most electric clothes dryers and AC units run on 240 V loads.  If you have to manually enter voltage into the Efergy unit, how can it determine total power consumption if you have your AC unit (240 V) and your TV (120 V) operating at the same time?  The Efergy unit will read total current flowing through your wires, but the total power consumption it tells you will either be too high (if you entered 240 V into the unit) or too low (if you entered 120 V into the unit).

***Update - 9/3/10 - My original issue was solved, so I crossed out the text, but it is important to note that in U.S. installations, you must set voltage to 120-130 V!

***Update - 4/28/10 - Thanks to the help from Lyn and Juan from Energy Monitoring Technologies I have the Efergy InstallationSupplement-US & Canada.  In US installations, the Efergy unit uses 2 current transformers to measure current on both legs of the residential electrical service.  When a 240 V load is operating, it is merely pulling power from each of the 120V leg and adding the current from those two lines together in its logic.  For instance, your 240 V appliance may see 5 Amps at 240 V (1.2 kW) , but the Efergy meter will be recording two, 120V/5A loads (120*5 + 120*5 = 1.2 kW).  For all intensive purposes, it doesn't matter if a meter measures 4 Amps at 120 V or 2 Amps at 240 V, the math will come out the same.

But conservation isn't the only area where  a problem can occur.  Clean energy installations could also pose an issue.  The voltage on a solar panel array will fluctuate throughout the day based on how the inverter regulates the Maximum Power Point.  Basically, the inverter will fluctuate the solar array's voltage output so the power is alway at its maximum.  If the voltage fluctuates, the Efergy unit is going to be unreliable!

***Update - 4/20/10 - Thanks to some helpful comments below (thanks Lyn, Suzi, Juan, others) I'm not so worried about the accuracy of the Efergy meter, but I would like to hear about people who have tested the Efergy's accuracy against their residential meter or used it to monitor a solar panel installation.  See Lyn's comments below about where he sets his voltage setting at.