Utility Meter Accuracy

Well I have to admit that I'm stumped with an energy audit I've been working on for the past two months. Perhaps someone can point me in the right direction...

My client contacted me concerned that his electric bills were atrocious. They were, to the tune of 34,680 kWh per year (average monthly at 2,890 kWh, and a baseline of 2,347 per month!). And after my first visit to his home, it was very obvious to me that, although he has a big house (3700 sq-ft), he and his family of four were energy frugal, being careful to shut off lights when not in use, using power strips for entertainment centers, etc.

He was particularly concerned about the phantom consumption when he and his family would leave for several weeks at a time. When they did he'd shut off everything but the alarm system. And even then he'd see a bill of 1900 kWh for that month, and for what?

So I dove in deep, taking this on as a personal project, since he'd had an auditor from the utility company come out previously and they couldn't find anything. One of the first things I did was to install a PowerSave EnviR monitor on the two mains into the main circuit panel and let that thing collect data for exactly two weeks. I compared this kWh total to what the utility company's meter read and found a discrepancy of about 500 kWh in favor of the utility company. This closely paralleled the additional 10k kWh per year that I could not account for in my projected analysis. Hmmm.... found it! (or so I thought)

So I got on the phone and was soon in touch with the supervisor of the electric meter department. I told him my findings so he and I got together at the client's home one day so that he could test their equipment, which consisted of a transformer/transducer system which reduces the incoming current from the main transformer at the street. After a good hour of testing he informed me that their equipment tested okay. Hmmmm.... bummer.

After many hours of monitoring individual circuits, extrapolating the long-term consumption, I still can't account for this additional 10k kWh per year anomaly. I even looked for hidden conduits coming off the wiring gutter under the transformer, assuming a neighbor might be "borrowing" some power for their growing operation. Nothing. Absolutely nothing.

And now that I've been so thorough with my investigation and extrapolation, I'm left scratching my head, wondering if, even though the utility company tested their equipment as good, perhaps it is not over a long term. I honestly don't know where to go from here... Suggestions?

Tags: accuracy, meter, utility

▶ Reply to This

Replies to This Discussion

Permalink Reply by Tom Delconte on July 13, 2012 at 1:18pm

You didn't mention what type of meter he has. Normally utility companies are happy to do a swap-out of the old meter at the customer's request. Sounds like you and your client are between the rock and the hard place on this one with this utility company, whoever they are!

▶ Reply

Permalink Reply by Rod Fox on July 13, 2012 at 2:39pm

The meter is a digital type, having already been swapped out for the analog type about a year ago when the client first started complaining about their consumption.

The utility company is PNM, in north/central New Mexico.

▶ Reply

Permalink Reply by Bud Poll on July 13, 2012 at 1:29pm

Hi Rod,

Since you have a number that is in the ball park and clearly points to the power company side, try asking them what meter they would recognize for long term monitoring.

For additional testing, have you tried turning off all breakers on the main to see if the reading stops advancing. And what type of meter do they have, new digital or the old turning wheel? If the meter continues to advance with all breakers off, there is a concern that there might be some leakage to ground or between hot leads between the meter pan and the main panel. This is not good. Besides extra electric, there is a fire potential.

What is the routing between the meter pan and the panel. Any long runs or paths underground can be suspect.

Bud

▶ Reply

Permalink Reply by Rod Fox on July 13, 2012 at 2:46pm

I did actually turn off all breakers on the circuit panel when monitoring with the EnviR monitor. When I did, the consumption was at 0 watts. Didn't think to look at the utility meter at that point though (d'oh!).

As for the routing, the main feed comes into the utility owned box where the digital meter is. Around each lead are transducer donuts with leads going to a transformer and into the meter. From there, it goes to a disconnect/bypass, then into the house via the gutter (not the one for rainwater). The run from the disconnect to the main panel inside the house is less than 8 feet.

When the utility guy checked their equipment, he ran diagnostics on both the meter and the transducer/transformer equipment.

▶ Reply

Permalink Reply by Rod Fox on July 13, 2012 at 2:53pm

Also Bud, I did ask them the question of what they would recommend for monitoring. They had no recommendations other than to "trust their equipment". Right...

▶ Reply

Permalink Reply by Bud Poll on July 13, 2012 at 3:17pm

With the breakers off your meter at the panel read zero. They tested their meter and it IS good. The extra current is being lost between their meter and the main panel. Shut those breakers off again and watch the meter to see if it is still advancing. If it is, then you will have confirmed a loss between the meter and the panel and you can demonstrate that to the ho and electrician.

I don't know how confident you are with opening boxes, but, if you can attach your meter at the disconnect you can test some additional length of wiring. That could pin point the issue to between the disconnect and the house or between the disconnect and their meter.

Bud

▶ Reply

Permalink Reply by Rod Fox on July 13, 2012 at 5:19pm

Good advice Bud. Problem is, the clients are away on vacation for another week (in Italy, poor saps) and I can't get onsite to do so. Then I leave for Seattle for three weeks on Tuesday...

Sure would like to get paid for this job...... :p

▶ Reply

Permalink Reply by Bud Poll on July 13, 2012 at 6:21pm

If their meter is correct and your meter is correct, then there is power going somewhere in between those points. For the jobs that don't pay enough, you can always justify the time as OJT.

Bud

▶ Reply

Permalink Reply by Sean Lintow Sr on July 13, 2012 at 1:59pm

Most I have heard consider being within 2% "accurate" - that is something you would have to check with your utility

One example can be found at www.pepco.com/home/billing/understand/accuracy

You could also do what Tom says & see about asking to switch it out

▶ Reply

Permalink Reply by Rod Fox on July 13, 2012 at 2:51pm

I did contact the manufacturer of the EnviR monitor to check on what they claim is the accuracy of their unit. They replied saying that it should be within 2% of what the utility meter reads. In our case, the EnviR monitor read 1416 kWh and the utility meter read 1920 kWh for a two week period; a difference of 504 kWh and 25%!

2% would be great!

▶ Reply

Permalink Reply by Bob Blanchette on July 14, 2012 at 7:31am

If the meter has already been exchanged I seriously doubt you have TWO inaccurate meters. No chance it's a "smartmeter" that can send the power use to a website?

▶ Reply

Permalink Reply by Rod Fox on July 14, 2012 at 12:39pm

PNM does not yet implement smart metering...
There is talk about it, but I doubt we'll see if for at least another few years at the earliest

(http://www.pnm.com/regulatory/pdf_electricity/irp_2010_smart_meter_...)

I don't suspect the meters are the culprit here, particularly because they've been swapped out. What I DO suspect is the transformer/transducers that feed the meter its information.

▶ Reply

‹ Previous
1
2
3
4
Next ›

RSS

Welcome to
Home Energy Pros

Sign Up
or Sign In

Or sign in with:

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy, under the American Recovery and Reinvestment Act) and brought to you in partnership with Home Energy magazine.