Kudo’s to @kevin1 for his work in comparing SENSE to the Utility. I wish I could do that type of analysis, I also wish I could understand it all. Some of it yes, some of it is over my head.
I used to be a meter tech a long time ago and still like to keep up on as much as I can, but time marches on. I wrote a little information on comparing SENSE to the utility meter. I hope it helps anyone who wants to know.
This is a picture of my electric meter. Notice the black bar beneath the numbers. This bar moves across the dial. The speed is in proportion to the watts the meter is reading at that instant. If you want to compare your meter to your Sense reading, all you need is a stopwatch and a calculator. Your smartphone has both.
Every meter has a watt-hour constant, (kh) The constant on most of the Digital Meters is 1, and it will show on the face of the meter. The definition of kh for a solid state meter is - The number of watt-hours represented by one increment (pulse period) of serial data. For an electrical mechanical meter the kh is called the Disk Constant, and it is the number of watt-hours represented by one revolution of the disk. The disk constant will be a different number like 3.6 or 7.2.
For the digital meter this means that one pulse = 1 watt-hour. That means it takes 1000 pulses to equal one kWh.
To measure the load, you are going to time the pulses. This is what metermen call a stopwatch demand. It is an instantaneous reading of what the meter is reading in watts.
The formula is:
Watts = 3600 x kh x revolutions divided by seconds.
Kh is a meter constant that is shown on the dial
Revolutions is the number of pulses shown on the dial (the moving bar) each time it moves is one pulse (or revolution).
Seconds is what you time as the pulses are indicating.
Example:
MY house, my pool pumps were running and Sense was showing around 3688 watt. I timed 6 pulses for 5.69 seconds. 3600 x 1 x 6 = 21600 / 5.69 = 3796. Pretty close. The trick is to have a constant load.
If you have a heavy load, AC running, pool pumps running, car charging, etc. the bar will fly by. My meter has 8 bars. With a heavy load I count the last in line and multiply by 8. Some meters may just have a black square that blinks off and on, but there should be some indication you can time. If you have a small and steady load, you will be pretty exact. With a large load it may vary a bit. The key is to have a constant load and be exact in your start and stop timing.
There are many different types of meters and yours may be different. I am in Southern Nevada. Some meters may even give you an instantaneous or current reading. It also depends on the Utility providing the service.
This also works with meters that have a revolving disk, I don’t know if there are any of them around. If you have a disk, time the revolutions of the disk, there will be a black mark to start and stop the time. Do at least 2 revolutions of the disk, no more than 10 are necessary.
You can also Google “kh meter constant” for more information.
I hope this helps those who are trying to verify the accuracy of the SENSE reading. Remember the more constant the load the more accurate you measurement will be.