Lots of folks involved in the 1000 Home Challenge have effectively tackled their electric plug loads.Low cost devices such as the Kill A Watt meter (~$30)  can provide useful information that help direct their actions. Consider that the average US family uses more than 25 kwh/day, and some of our homeowners use less than 5 kWh/day. Pursuing baseload through a combination of equipment, controls, and behavior can be quite cost-effective. 

Recently John Morgan, who is the 18th person to meet the 1000 Home Challenge  asked me about their accuracy. He was monitoring use of several portable counter top induction cooking units. 

Please chime in - 

Are there significant differences between inexpensive Do-it-Yourself (DIY) plug-in type electric meters?

Are some more accurate for certain types of loads? 

How do they differ from more expensive meters?

Which ones do you recommend, and for what applications?

How can one easily check their accuracy?

What are practical considerations - features that give a meter more value to the user?

Provide links to useful resources


Tags: 1000, Challenge, Home, electricity, feedback, loads, low-cost, monitoring, plug, use

Views: 870

Replies to This Discussion

Here is a useful link:


This 2011 study included the following passage on why they chose to use the Watts Up Pro:


"...researchers selected the Watts Up Pro ES meter because it had the following features:

  • Ability to record and store data from a single plug load device rather than a circuit or electrical panel
  1. Ability to record data at one or twominute intervals
  • Ability to store data for multiple weeks
  1. Ability to record true root means squared (r.m.s), which is a statistical measure of the magnitude of a varying quantity, watts, r.m.s. volts, r.m.s. amps, voltamps, power factor, and add a date and time stamp for each interval recording
  1. Userfriendly character (provided clear documentation, was easily programmed, and downloaded data quickly and accurately)
  • Ability to record entire range of power for office plug load devices (<1 watt up to 1,800 watts) with same model meter
  • Sufficient level of accuracy in specifications for this study. Meters evaluated in the research team’s
  • laboratory met the stated specifications.
  • Desired price point
  • Timely consumer availability (in 2007)

Researchers programmed the meters to record watts, volts, amps, voltamps, power factor, and maximum wattage at oneminute intervals. With these settings, the team was able to record a maximum of 23,752 readings, or 16.5 days worth of oneminute interval data. The desired file length was 20,160 readings at oneminute intervals — exactly two weeks.

Thanks Barbara - 

Great info. I have limited experience with the Watts Up Pro. Appears to be a good product, particularly if you want to evaluate the energy use pattern of the monitored equipment.  That could be quite useful if you are evaluating energy use with different control strategies. 

Hello Linda!

I'm not going to answer each of the important questions you raise but want to say that I recently purchased the basic e2 system from efergy (lower case) and have confirmed it's operation. The e2 system uses a pair of current transformers in the main panel to feed a transmitter that wirelessly communicates with a portable, hand-held monitor. Purchase price ($115/shipped after discounts) and includes downloadable logging software and a USB interface to a laptop or desk top. A trip to their site is informative. (Google). efergy was founded in Britain and now works with utilities around the world, including the US.

I'm away from home through October and plan to give the equipment a thorough workout upon my return. The most intriguing aspect of their system is that it permits users to walk through a home (or business-3 CT inputs are available) and see an immediate (OK, 6 sec) kW response on the monitor as loads are switched. Neato!

I bought the equipment in order to learn where 10kWh/day are being used in my empty home (thanks NVEnergy for smart meter data! Too bad it's only available the day after :( ).

Here's what efergy's equipment looks like.

Film at 11

All the best.

Thanks Steve!

I look forward to finding more info about this system. Sounds like it would help track down parasitic loads. Anyone else have experience using this system? Sounds similar to the TED, though less expensive.

The problem with plug in energy testers is they miss most of a typical homes energy use. 240v appliances account for the majority of electricity power use, yet there is no easy solution to monitor them.

"The problem with plug in energy testers is they miss most of a typical homes energy use. 240v appliances account for the majority of electricity power use, yet there is no easy solution to monitor them."

Correctamundo, Bob!

With a CT on each leg of the incoming power, I believe the e2 will meet that challenge.

Here's a picture of why I have to delay installation at my home. A bit tight. I didn't mention in my first post that I checked out the unit on son Dave's easily accessible panel at his home in Berkeley.

I attempted to use an AZTech device. I have used the Watt Stopper, Watts Up Pro, Kill-A-Watt and Kill-A-Watt EZ. I also have a custom-configured SEL 5030 revenue meter which SEL's metering program donated to my energy conservation education program.

If you're working with someone who has the knowledge and financial means to use the SEL device, use that. I highly recommend it. It's an amazing piece of equipment. 

I serve people who participate in the LIHEAP and WAP programs. They have low to moderate incomes, may or may not have physical or mental disabilities, and may or may not have strong academic backgrounds. My first preference is the Kill-A-Watt EZ by P3. It's easy to use and affordable, and its level of accuracy compares to the SEL device.

P3 offers a similar product to the "Kill-A-Watt EZ" called the "Kill-A-Watt". Between the "Kill-A-Watt EZ" (~$30) and "Kill-A-Watt" (~$25) I much prefer the Kill-A-Watt EZ. It calculates operational cost, whereas the other model does not. When I'm in home, I'm providing instruction on energy conservation--a topic already perceived as "hard". In most instances, the last thing I want to do is branch out into a mathematics lesson on calculating operational cost. Further, $5 USD for the elimination of that much possibility for error is worth it to me. The drawbacks to both P3 products include:

  • They are not DOE-approved metering devices and therefore cannot be used for formal appliance monitoring in the Weatherization Assistance Program (WAP),
  • Sensitivity to overload (I encountered a bad electrical panel at a residence, and my Kill-A-Watt "blew" at 135V),
  • Sensitivity to shock (drop it once, and it's probably ruined),
  • The need to "zero out" data...every.single.time (does not clear upon disconnect), 
  • The inability to store data from multiple appliances or multiple monitoring sessions, and
  • The inability to monitor 240V appliances.

My second preference is the Watts Up Pro. It is DOE-approved for use in WAP, has superior data storage capacity (the device has the ability to store multiple readings from multiple appliances) and is more durable than the P3 devices. It is also 3 to 4 times the cost and a little more difficult to figure out how to use than the Kill-A-Watt EZ. Like the P3 devices, it cannot be used to monitor consumption by 240V appliances.The majority of home owners and occupants I serve don't have the patience for it. Half my coworkers don't have the patience for it.

I was not at all impressed with the Watt Stopper. While it is also DOE-approved for use in WAP, the 3 units I've used performed so poorly that the meterings had to be redone with the Watts Up Pro. The Watt Stopper also cannot be used to monitor consumption of 240V appliances.

The AZTech devices are intended to interface with smart meters, so they could feasibly be used to monitor both 110V and 240V appliances. However, the devices I tested did not work. I tested a sample of 5 units from a lot of 30+ which had been donated to our program by a utility company, experienced the same result with all 5, and discarded the lot.

I've not used Wattson or TED. Here are some scholarly articles by those who have.

  • "Wattsup?: Motivating reduction in domestic energy consumption using social networks" by Derek Foster, Shaun Lawson, Mark Blythe and Paul Cairns 
  • "Pilot Evaluation of Energy Savings and Persistence from Residential Energy Demand Feedback Devices in a Hot Climate" by Danny Parker, David Hoak and Jamie Cummings
  • "How Much Energy Are We Using? Potential of Residential Energy Demand Feedback Devices" by Danny Parker, David Hoak, Alan Meier and Richard Brown
  • "Promoting Energy Efficient Behaviors in the Home through Feedback: The Role of Human-Computer Interaction" by Jon Froelich

While smartphone technology and Internet applications aren't among the discussion points listed, I've reviewed some apps and read articles on that as well. At this point, I'm not impressed with what's out there. The developers don't understand an energy audit, blower door, duct blaster, or residential billing analysis, they don't do a good job of incorporating GIS and climate data, and in some cases they dole out bad advice that is 20 years or more out of date (such as "wrap your water heater").

Some web-based applicaitons from utility companies are better than others. Rather than go with something which works well in some instances and is still in developmental stages in others, I strongly recommend the DOE Energy Star Home Energy Yardstick, which is a web-based application suitable for almost every dwelling type *except* multi family housing which is on a single utility meter.

The thing I don't like about the Home Energy Yardstick is it does not differentiate between cordwood and wood pellets as fuel sources, which is significant as wood pellets tend to be more efficient than cordwood.

Interesting topic! 

I've used the efergy Elite whole house energy monitor to evaluate 240V HPWHs. I found the accuracy varied as much as 20% due to the quality of the CTs. I tested and matched up the good ones and created matched pairs of the ones with known errors, then put in a correction factor when I downloaded the data to Excel. Not the best solution, but close enough for our study. We used efergy as it was the best of the lot of home energy monitors with the features we wanted (data storage, downloadable to a laptop, Zigbee wireless).

While I have found the quality of most home energy monitors to be barely acceptable, I think they can be useful for monitoring electric water heaters, well pumps, sub panels, and other questionably high loads.

We looked at the TED several years ago and found that they used both ZigBee and PLC (power line carrier). We found reliability issues with the PLC part of the system, especially when there was powerline noise. Otherwise, I liked it.

I like the capabilities of eGauge and eMonitor. While meant for long-term installation, they can give a detailed picture of electrical use. Combined with HeetMeter to monitor a gas or fuel oil furnace or boiler, one can get a complete snapshot of energy consumption.

Here is a response from Larry Kinney

A few years ago someone had a gee whiz calibrated watt and watt hour meter testing device at ACEEE…cost $10K or so.  So I got him to test a Kill a Watt I happened to have in my pocket.  It was within 1.5% on all scales.  Plenty good enough for what I care about. 


Further, years ago I got tired of trying to make sense of the directions that come with the meter so wrote up something that seems to be useful.  Attaching a copy you are free to use, trash, or edit.


Best wishes, Larry


Larry Kinney, PhD

Chief Technology Officer

Synergistic Building Technologies

1335 Deer Trail Road

Boulder, CO  80302, USA

303-449-7941 (voice)

303-579-1439 (cell)




Here is a response from Frank Bergamachi (Thousand Home Challenge project #4)

I’ve looked into this and my recollection is that both the Kill-a-watt and the TED 1000, both of which are inexpensive and handy and  I’ve used extensively, are relatively accurate and account for power factor. However, the TED has a resolution problem in that it reports in 10 watt increments (the manufacturer tells me in records much more accurately). Often I am looking for “leakage” at under 10 watts, (using Danny Parker’s methodology of monitoring the mains while branch circuits are turned off) so it’s of limited use for me in that regard.






Frank A. Bergamaschi, Architect

Leed Accredited Professional, USGBC

Nationally Certified Sustainable Building Advisor, SBAi

1045 Sansome St #201

TELEPHONE: (415) 398-9520

FACSIMILE: (415) 398-0135


Hello all,

Finally made time to install the Efergy E2 system I bought and here's an email I sent to my contact there detailing the process. My photos did not copy/paste and I've added them separately. I'm sure you can determine where they fit.

Hello again Peter.

I trust this finds you and yours well!

I finally made time to install my equipment and want to share a few photos of the procedure. As you may recall, space inside my panel is quite limited:

...and although there may appear to be adequate room, installing your CT's was a time-consuming job that took somewhat over an hour. Next time, I'm sure I could easily cut that time in half.

After several unsuccessful tries at a straightforward installation, my only option was to shut down the main breaker and pull all the other breakers out of the panel. I probably could have left a few at top and bottom, but it turned out to be easier to just remove them all. It looks worse than it was, since they snap in and out easily and wire lengths ensure they go back in proper order.

Keep in mind all the breakers were "cold" and I wore long rubber gloves while working inside the panel. Even with everything removed, accessing the large, main feeds was a challenge and I had to bend the wires apart somewhat to install the CT's. Also, the top CT was such a tight fit that I had to separate the two halves of the "clam shell" and put the unit back together after it was in place around the main wire.

Those two main feed lines make a tight, 180 * turn and go behind the main buss bar.

Here's how the lower part of the panel looks with everything back in place. I'm looking for a proper grommet to replace the electrical tape. My panel is deeply inset and the knock-outs were not useable, so I had to drill a new hole.

And the finished product. I have textured paint on the panel door and that, along with a 25F ambient, conspired against the double sided tape on the back of the weather-resistant enclosure. Notice the self-tapping screw. And yes, I closed and latched the panel door later.

Linking the transmitter and monitor was simple and just before bedtime, I spent an hour, without success, trying to make the last 150 W go away. I set the transmitter for a 6 second refresh and it was amazing to walk around my home watching kW on the monitor drop as I turned off plug loads. I'll be checking my NVEnergy portal tomorrow to see how low nighttime use fell.

So,far I'm delighted with your product and I'll be in touch again after I download your software and connect the E2 monitor to my desktop.

All the best.

From IPad: Steve Waclo, EE ret.
1171 Bandtail Drive
Carson City, NV 89701
775 883 7927
Upload issues with pics.


Latest Activity

Danny Gough replied to Danny Gough's discussion REALLY????
"As I have read through everyone's excelent responses, it has caused me to reassess my…"
20 hours ago
Tim O'Brien replied to Danny Gough's discussion REALLY????
"Bradford - I have seen single family homes with ducted central AC or heat pump hold enough water…"
Brett Little posted an event

How to Make Money by Cutting Your Home's Carbon Footprint, Heating Bill, and Electricity Bill to Zero - Free CE Webinar at Webinar Online

June 12, 2019 from 12pm to 1:15pm
How to make money by cutting your home's carbon footprint, heating bill and electricity bill to…See More
Emily Ambrose posted a blog post
Building Performance Institute commented on Emily Ambrose's blog post 4 Signs Your Website Is In Need of A Refresh
"Excellent food for thought! Thank you!"
Building Performance Institute liked Emily Ambrose's blog post 4 Signs Your Website Is In Need of A Refresh
Bradford E. White replied to Daniel Baur-McGuire's discussion How to Insulate Exposed Outdoor Ductwork?? Help
"One system we specify was a contractor suggestion. The "old way" was board insulation and…"
David Keefe commented on David Keefe's video

A Climate Report From The Field - Dave Keefe

"Thanks Colin, I appreciate that."

© 2019   Created by Building Performance Association   Powered by

Badges  |  Report an Issue  |  Terms of Service