Potential Causes of Electric Meter Showing more power consumed than alternative measurement device

Question

I have lived in a house for awhile that seemed to have an awfully high reported electric power usage. Like shockingly high, with nobody home in the winter (meaning no AC usage) we were seeing numbers like 100kWh per day. And over the summer that number jumps up to 140kWh. (this is a house in the northeast USA, so not too many days a year that the central AC even gets run)

This seemed to be the case regardless of upgrading all the appliances to high efficiency ones, changing out all light bulbs for CFLs then LEDs. Basically doing everything imaginable to reduce energy consumption, had almost no impact on the billed kWh usage.

So a few days ago I got a Sense home electric monitoring tool, and installed it on the split phase main right as they enter the house in my breaker box. The power it reports is exactly what I would expect to see. If I turn on 60W worth of light bulbs, the consumption jumps by 60W. Everything with this device seems to be pretty darn accurate.

Except that it is reporting less than 1/2 of the power consumption of the electric meter. Last night during a 12 hour period, the electric meter went from a reading of 88784 to 88832, or 48kWh being reported consumed, while the Sense device reported that 18kWh was consumed during the same period.

Other than a defective electric meter (which is possible, but I consider it to be a long shot) can anyone else think of any other way in which an additional 30kWh could be reported as consumed with no apparent restive heat source sitting there burning it away? I have considered reactive power somehow, but I don't have any large inductive loads that I could think might be phase shifting by that much.

The meter is at a barn which is about 700 feet of cable away from the house, but 700 feet of 4 aught cable wouldn't possibly burn any meaningful amount of power in a I^2*R fashion at 240V over that distance.

I've read a few places people talking about "deviations to ground" being a source of energy loss. Is it even possible that could be the case here with that much power? And if so, how would I even start trying to hunt such a thing down?

Answer 1

100 KiloWatt-Hours a day? (a tick over 4 KiloWatts continuous, that's nine 400W sodium lights burning 24x7) with nobody home? Summer and winter? That's murderously wrong and I would not put up with that for one minute let alone one month.

It would help to have a "second opinion" meter up at the meter. It wouldn't work to put the Sense there, as it relies on listening to subtle signals that won't make it 700'. The upshot of the 700' is that voltage drop becomes very, very important. Pay close attention to your instantaneous voltage and current numbers coming off the Sense. Any appreciable voltage drop indicates you're spending a lot of money making 700' of wire warm. 1400' of 4/0 cable is 0.1124 ohms.

It would help to get instantaneous kw (not kwh) readings from the meter. Back in the day you'd look at the spinning disc with a stopwatch, but hopefully your smart meter has a way to read it.

700' is a lot of property to secure

I am puzzled at why the power company gave you power 700' away from the point of use, instead of traversing the 700' at 2400 or 9600 volt distribution voltage. There must be a reason; that reason might have something to do with it. I can't guess the whole story, but large properties often have complicated things going on.

Such a large spread (and cable run) is hard to secure, so illegal tapping is a possibility. (marijuana grow, typically). So it's very important whether there are any other structures near you where that would be possible. Criminals may have tapped anywhere along the 4/0. 100kw/day is 17 amps at 240V, interestingly at the limits of 12AWG wire (the criminals don't care about voltage drop since you're payin'.) Under these conditions (12AWG/17A)voltage drop will be 6 volts per 100 feet, so the thief could be 500 or even 1000 feet away and still get usable power. Modern ballasts and LEDs will run on any voltage 100-277V.

If you find a rogue cable, typically cheap Romex, go no further and call the sheriff or state police. They know what a rogue cable means, and they'll come in sufficient force.

You might also consider any legal use by other facilities on the property, especially ones where electric heat might be in use. (forgotten fallout shelter? Sorry, just watched 10 Cloverfield Lane.) In simplest terms, look at what cables are exiting the meter pan. It should only be the supply and your 4/0. Does your 4/0 make any other stops on the way to your house?

Chase it

Now it's go after it with the measuring devices (assuming you get an ammeter you can use up at the meter pan, e.g. the meter itself).

I would turn off the main at the house and go up and look at the meter. If the meter stopped, it's a transmission (voltage drop) problem which I agree isn't likely if the cable is really 4/0. I suspect you'll still see a ~4KW load... and then, you have to check other loads.

You will want to check current on every conductor, and also on every ground bond, including the one at the transformer.

• If power is leaking from a hot to earth, it'll show up on one ground bond or another, likely all of them. There should never be current on that except during a lightning strike.
• If you see equal current on both hots, that's a 240V tap, probably a bad guy.
• If you see equal current on one hot and neutral, that's a 120V tap, 4kw is a lot for 120V so something funny is going on.
• If you see imbalanced currents on hots and neutral but the lower hot + neutral equals the higher hot, that is a 120/240V tap, criminals wouldn't bother, that's more likely a proper load on your property.

If all else fails, have somebody come out with a FLIR camera at 5am and walk the cable route. 4KW is a lot of heat, like 3 burners on your stove going full tilt. That will show up on a FLIR, and if it's leakage in the cable, there'll be a red spot on the ground above it.

You might have the power company pull the meter to allow you to unhook the 4/0 - and then reconnect the meter, and see what it does. Or perhaps your generator interlock provides a way to do the same thing.

• If you still have 4KW of load, then you need to chase other taps of that meter.
• If disconnecting the 4/0 ends the load, and your house is the only load on the 4/0, then you have a tap of some kind, either one of yours you don't know about, or a crook.

Lastly I need to at least mention the generator and interlock; make sure all that is in good order. Again, a 5am inspection with a FLIR will expose a ~4kw drain.

Answer 2

If the cable running to the house is damaged and the insulation is leaking current then it could be running up your bill.

What you really want to do is get an Ammeter on the wires that feed the house at the barn and turn off the main at the house. If there is any current flow to the house it is leaking insulation on your cable/wire to the house and all you are doing is heating the ground with the wasted electricity.

Your utility company or a reputable electrician could come help you test for this if you do not have the tools or desire to get into the panel at the barn.

An average residence consuming 100kWh per day with no one at home is extreme unless you are running a grow operation.

You should have this checked out immediately and save yourself some money.

Good luck!