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
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:
Researchers programmed the meters to record watts, volts, amps, volt‐amps, power factor, and maximum wattage at one‐minute intervals. With these settings, the team was able to record a maximum of 23,752 readings, or 16.5 days worth of one‐minute interval data. The desired file length was 20,160 readings at one‐minute 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.
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.
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:
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.
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.
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
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
SAN FRANCISCO,CA 94111
TELEPHONE: (415) 398-9520
FACSIMILE: (415) 398-0135