You can check your electric utility meter by yourself without any special tools in about 5 minutes.

What you need:

• One electrical plug-in load

• Optional: plug-in KiloWatt meter

• Stopwatch or smart phone

The plug-in load can be a portable space heater, or an electric kettle or even a microwave, anything that is rated at about 1500 Watts and plugs into an outlet. The plug-in meter is not needed if you know the consumption of the load.

NOTE: Many space heaters rated for 1500W are closer to 1300W as soon as they warm up.

The measurement works best if the electric consumption in your home does not change during the measurement. The easiest way to achieve this is to turn off all breakers, except for the outlet that you are using for this test. If you rather not deal with internet outage and other by-effects of the power being turned off, then make the consumption as stable as you can - nobody turning things on or off during the measurement and you wait till the fridge is either starting or just stopped running. Also, now you need to do two measurements: before you turn on the load, go to your utility meter and with the stopwatch, measure the time that the disk takes to spin around once, this is your “baseline” measurement, write down the time. Now plug your load into the plug-in meter and  turn on your load, read the plug-in meter to see how much this load draws. Then go to your utility meter and measure the time that the disk takes for one spin. If you are not sure that you measured correctly, simply redo the measurement until you time the moment the painted mark passes correctly with the start and stop of the timer. 

Write down this “loaded” time measurement. Turn off the load and you can redo the first “baseline” measurement to verify that the consumption has not changed during the measurement.
Also write down the Kh number that is listed on your utility meter.

If you had turned off all but one breakers, you now have only the “loaded” measurement and can do the calculation:

• Kh x 3600 / (“loaded” time) = consumption in Watts.

  • • For example, Kh is 6 and the time you measured was 18 seconds:

• 6 x 3600 / 18  =  21600 / 18 = 1200W

So your utility meter recorded a consumption of 1200W and you can check if the plug-in meter also indicated that your load has this power consumption.

If you did not turn off the breakers, you have two measurements and we need to do two calculations and a subtraction. This should take about 5 minutes:

• If the first “baseline” measurement you did was 36 seconds and the second “loaded” time measurement was 10.8 seconds, then do the calculations:

  • • 6 x 3600 / 36 = 21600 / 36 = 600W “baseline”

    • 6 x 3600/10.8 = 21600 / 10.8 = 2000W “loaded”

• The load apparently added: 2000W - 600W = 1400 Watts, you can now verify with the reading of the plug-in power meter if that was correct.

My home has a Westinghouse model D4S meter, which was produced by that company between 1968 and 1983, see: Modern Electromechanical Meters. As you can see in the image of the meter above, it has a spinning disk with a black painted section, just above the model indication “type D4S”. The Kh indicated on the meter is 7.2.

I have a whole house electronic meter that indicated that the whole house including the fridge that was running at that time, had a stable 200 Watts consumption. I filled the kettle with water and turned it on, the reading rose by almost 1500W to just under 1700W, and slowly as the water was heating up, the reading decreased a little to end at just over 1660W after the measurement so an average of 1680W. As soon as I turned the kettle on, I walked over to the utility meter, and when the black mark on the disk touched the line above it, I started the stopwatch and stopped it when the mark was in the same position again 15 ½ sec later.

So, I did the calculation: 7.2 x 3600 / 15.5 = 1672W registered by the utility meter while the consumption indicated by my electronic meter was on average 1680W. Apparently my meter is calibrated correctly with less than half a percent error according to this verification.

You see two dates listed, 1/17 and 2/20 which means that the meter was read on those days, so the consumption is from the period starting 1.5 month ago until just over a week ago, because the bill is prepared just before 3/1 when it is due. The number of days in this period is: 1/17-1/31 so 14 days in January and 20 days in Feb. Total 34 days. The meter readings on those two days are listed next, then the difference between those two is calculated to give the consumption over those 34 days. Lastly, you see that the consumption in the previous period was almost identical: 355 instead of 358 kWh. (Geek alert: note that the bill writes the Units incorrectly as KwH, exactly the opposite capitalisation as is standardized.)

Now, for you to be able to verify if the meter readings are correct, you need to read your electric meter regularly if you have the standard mechanical meter. Say that you read the meter about every week and wrote those down together with the date:

• 10400 1/1

• 10480 1/8

• 10560 1/14

• 10640 1/21

• 10720 1/29

• 10800 2/6

• 10880 2/13

• 10960 2/20

• 11040 2/27

It is easy to see that the 1/17 meter read of 10603 is pretty much in the middle between your 1/14 and 1/21 meter reading dates which were 10,560 and 10,640, so that looks like the correct amount as the middle of the two readings is 10,600.

The 2/20 reading is even easier, because you read the same day and just one kWh from the reported reading, so your bill seems based on the correct amounts.