Power Consumption and Registration Issues for Smart Meters

by K. T. Weaver, SkyVision Solutions, November 14, 2017

There has been recent opposition to smart meters based upon claims such as the following:

“The power required to run the AMI meter is borne by the homeowner, this was never disclosed to the public that their bill will go up by over ~$115.00 per year just to power the meter.”

I disagree with the above claim and will provide various levels of evidence on this webpage to demonstrate that electric utility meter electronics are actually powered from line voltage that is not registered as consumption for the consumer.

There are lots of reasons to oppose smart meters, but how much power they consume and whether it is registered by the meter is not one of them.

Design evidence demonstrates that smart meter electronics are powered by the utility line voltage, and the meter power usage in any case is quite small and wouldn’t be much of a factor to the individual consumer even if it were registered to the customer.

Naperville Smart Grid Initiative (NSGI)

My first exposure to the controversies surrounding smart meters started in my local residential area in the 2011 and 2012 timeframe when the City of Naperville received Federal funds to help install smart meters for its residential customers.  Very early on, the City was asked:

“How much power does the new meter draw?”

To this question, the City responded:

“The smart meters draw various amounts of power depending on their communication technology and manufacturer design.  The power to run the smart meters is not metered to the customer and is considered ‘line-loss’ energy consumption to the Department of Public Utilities-Electric.”

Since that time, I have not encountered credible information to make a different conclusion than was supplied by the City of Naperville several years ago.

Florida Power & Light (FPL)

FPL answers a similar question as posed above at https://www.fpl.com/smart-meters/faq.html, where it says: 

Do I have to pay for the cost for electricity needed by the meter to transmit usage information to FPL?

No.  There are essentially two “sides” of the meter – the source side, which is the utility side, and the demand side, which is the home and business side that is used to calculate your bill.  The power used to drive the meter and communicate with FPL is obtained from the source side of the meter and thus is not registered on the display, nor charged to the customer.

Meter Manufacturer Information

ACLARA Meter Specifications

Let’s look at how manufacturers look at the power consumption aspects of smart meters.  ACLARA (formerly GE) is one of the main manufacturers of smart meters.  Here is a recent (2017) meter specification sheet at this link:

https://skyvisionsolutions.files.wordpress.com/2017/11/aclara-i-210-residential-electric-metering.pdf

The image to the side of this page is from that specification sheet.  Notice where it says “Low starting watts; capture energy consumption at levels typically not registered by electromechanical meters.”

Elsewhere in the same sheet is says that the “starting watts” is either 12 watts at 240 volts or 6 watts at 120 volts.  An analog meter by comparison cannot normally register power consumption until it reaches something like 24 or 25 watts.  This can account for some of the differences one might see between switching from one type of meter to another.  If the power consumption of the home is between 12 watts and 24 watts as one example, it would not be detected by an analog meter but would with the ACLARA meter.

Also note that the specification sheet says “Low burden, which minimizes utility system losses.”  The utility industry normally refers to the power consumption of a utility meter as a “burden” as it truly is a burden to the utility and not registered to the consumer.  Since the burden is not registered to anyone, it is also considered to be among the many “line losses” in the distribution system that utility companies must face.  The specification sheet refers to a “typical watt loss: 0.7 Watts” which would be the actual power consumption value that ACLARA is claiming for its meters, i.e., a very “low burden.”  Note that this power consumption level would be nearly negligible to an individual consumer whether or not it could in fact be registered by a smart meter.

Elster REX2 Meter Specifications

The smart meter used in my local residential area is a version of the Elster REX2 model with specifications as given at the link below:

https://skyvisionsolutions.files.wordpress.com/2017/11/elster-rex2-ea-meter.pdf

For this meter under the category of “General performance characteristics” it says that the “Burden” is “Less than 1.5 W.”

In another document written by Elster it is stated:

“EnergyAxis consumes less energy during operation than other AMI/Smart Grid networks.  Due to highly efficient radio design, EnergyAxis residential smart meters consume as little as one quarter of the energy required in some competing smart grid solutions.  In fact, the energy savings across a large population of meters, over the system life cycle, can translate to many gigawatt hours of avoided system losses.” [emphasis added]

Again note how the manufacturer is boasting about how little power the meter consumes in order to avoid “system losses.”  If the power consumed by a smart meter were charged to the customer, this power would not be referred as a system loss.

Smart Meter Power Supply Design

According to Texas Instruments which has designed smart meter power supplies:

“Smart meters use more advanced communication interfaces as compared to conventional IR (Infra-Red) and IrDA (Infra-red Data association) interfaces; they also require more memory and a more powerful microcontroller.  These features increase the power consumption which necessitates the use of switch-mode power supply (SMPS) rather than a capacitive-drop power supply. …

Compliance with efficiency standards – and more importantly, compliance with lower power-consumption requirements – poses more challenges for SMPS designers as you cannot bill customers for the energy that a meter uses.  On the other hand, the smart meter energy usage should not place unacceptable power demands on utilities either. … [emphasis added]

The meter itself typically consumes less than 1W for most of its operating life, which is governed by the utility’s energy-efficiency regulations.  This high light-load efficiency is a main contributor to the average power consumption.”

Understanding How the Meter Electronics Gets its Power

To understand how the meter electronics gets its power, let’s first make sure we understand that when a utility meter is plugged into a meter enclosure with its “stabs,” current from the utility company is coming into the meter through the top connectors.  This is standard.  (see video below.)

Now let’s look at an expanded view of an Elster REX-type smart meter as shown in the graphic below.  In the components marked as “8 – voltage connectors,” these are the conductors that are in actual physical contact with the top meter stabs as utility supplied current enters the meter and thus also allows voltage to be supplied to the “4 – electronic assembly” portion of the meter.  In this configuration, there is no other alternative but to conclude that power being supplied to the meter electronics is prior to current flowing through the meter sensing devices which are inside the meter and which then at that point would register power being supplied to the customer’s load.

Elster Meter Isometric View

To further illustrate exactly how the meter electronics is supplied with voltage, below are actual photos taken during the course of disassembling a smart meter:

Elster REX2 Meter (3)

elster-rex2-meter-2.jpg

elster-rex2-meter-1.jpg

Sanity Check on How Things Work

Sometimes in confirming how things work with regard to smart meters, it is instructive to engage in a bit of a “sanity check” or mental exercise.  Consider for a moment that most smart meters being deployed today have a “remote disconnect” switch.  In fact, it is advertised that with smart meters, the utility can connect/ disconnect a customer remotely by switching the internal meter switch in the smart meter for reasons such as:

  • Remote Connect for Move-In
  • Remote Connect for Reinstatement on Payment
  • Remote Disconnect for Move-Out
  • Remote Disconnect for Non-Payment

If the smart meter were powered from the customer-side of the meter (with resultant registration of self-consumption power), once the customer were disconnected, then there would be no power to cause a “remote connect.”  This is especially true since many smart meters deployed today are not equipped with batteries.  What is actually the case, since the smart meter electronics are powered from the utility side of the meter, is that the meter remains powered, able to receive and send RF signals, even when the customer’s service has been disconnected through the remote disconnect switch.

Supplemental Information

The claim of someone’s bill going up by approximately $115 per year (due to smart meter power consumption) was based upon results by one individual in a home with a smart meter and whose home was unoccupied for a period of time and where it was believed there could be no electrical loads.  An unexplainable consumption level of approximately 100 watts as measured by the smart meter was attributed to the smart meter.  Even if some level of power consumption registration for a smart meter could be found to be attributed to the meter itself (see below), it is not plausible that the meter would be found to cause an average load of 100 watts based upon information you have already reviewed from this webpage.

Although the powering of the smart meter electronics has been shown to be a “burden” to the utility, I have read that during the course of measuring the current being supplied to the customer, there is effectively an interaction between the current sensor and the conductors passing current through the meter to the customer that results in a small amount of electrical consumption.  This consumption that is related to the current sensor could be on the order of a fraction of a watt (as a function of load) and would be registered by the meter as a part of the measurement process.  A similar registration process would occur with the traditional electromechanical meter.