Hi all,

I'm hoping someone can assist with a head scratcher I can't seem to crack. First, the facts:

Mostly heating climate (zone 5)

Home is 6000 sqft

GSHP (unknown EER/COP)

Rural home with a number of outbuildings for livestock and crops. The property is a legacy farm, but there is no active farming managed by the customers, aside from some 4H hogs. There is a separate meter for farm operations. There are six residents.

The only "atypical" things in the home are a hot tub, which is heated, a pool which hasn't been on in three years, and a tanning bed that is also unused.

Now for the usage:

Dec. 14 through Feb. 15 averaged 11,568 kWh monthly. For reference, that is more than the average annual residential usage for this state. Even the three lowest-usage months averaged 2,613 kWh per month. HDD for those months (Dec-Feb) average 1,239,

There were two additions in 2008 that added 3,200 square feet to the home. The customer indicates this is when the usage increased, as it should by adding that much sqft.

My first guesses as to the problem are that either the GSHP has some fundamental issue that runs aux. heat often/all the time, or that the residential meter is tied into the outbuildings with something drawing a lot of electricity.

My question for you colleagues is whether this usage is unreasonable for these parameters. There is no doubt whether it's a lot of usage, but I really don't know whether this is expected.

Don't hesitate to ask any follow ups, either, that will help drill down.

Views: 762

Reply to This

Replies to This Discussion

Since they are rural, they likely have their own well. Is the well on the same meter as the large usage?  If so, I would see if there were any changes in their water use.

These are my initial questions:

  1. Do you have data loggers on the heat pump? 
  2. Can you independently meter the hot tub? 
  3. What is the blower door number? 
  4. What size is the equipment? 
  5. What thermostat is being used?
  6. Where is the house?

2613 doesn't sound outrageous for a 6000 sf home with a well used, or poorly insulated hot tub.

Drill downs I would consider, based on anecdotes I hear as an energy researcher, who lives in our Everhart passive house. It is likely a combination of several things that use 200 kilowatts a month, rather than one big thing.

*I, too, am highly suspicious of any well pump and the hot tub efficiency--put a kill-a-watt on the hot tub circuit.

*Clothes dryer probably does 12 or more loads per week in a family of 6, could be an older one.

*Teen residents taking long hot showers or sneaking tanning bed sessions?

*Any tropical fish aquariums?

*Outdoor lighting from the old-school 375W spotlights?

*We researchers call it "plug load": Multiple, older refrigerators? Consumer electronics, high-end home appliances. I expect a large home has at least two large screen TVs, powerful home theater speakers, many set-top boxes, etc...some older products use 100's of watts and may be left on a lot, and even "off" position, taken as a whole, may be high. I have read that high-end kitchen ranges have a very high "off" usage. Electrostatic air filters.

I'll have people visiting the property next week, and the characteristics I've outlined above are based on conversations I've had with the occupants. The utility bills that come with that much usage are high, and prohibitively so for this family. They have cut all they can as far as electric usage, to the point that they spend their home time in blankets/sweaters/coats, so as a result I doubt their issues are with plug load including pets. Kids are all under 10 years old.

I think taking a deeper look at the well pump would be a good idea.

The only answer I was ultimately looking for was whether the usage outlined was patently absurd, i.e., there must be something wrong on the utility side of the meter. Sounds like that answer is not necessarily. I'll check back in next week.

To give some perspective, at 11,568 KwH per month, that would be 16.07 KwH per HOUR, or 67 AMPS at 240 VAC (134 amps at 120 VAC) running 24/7. Yes, that is HUGE for the situation described. Put an amp meter on those circuit breakers. A 1 HP submersible well pump (which is on the large side for residential) should draw around 10 amps at 240 VAC (about 13 amps for a 2 HP motor) WHEN IT IS RUNNING, which should only be occasionally. 

Energy can neither be created or destroyed, only converted from one form to another. If a hot tub is drawing a lot of electricity, it is either getting very hot or there is a lot of insulation missing and it is heating the outdoors. Hot tub heating elements are in the range of around 5 KW, but they don't run all the time.

There is a small possibility that an underground service entrance cable has a break in its jacket and is leaking electricity to ground. Turn all breakers off and see if the electric meter is still spinning. If it is, then either there is a tap off of it somewhere or there is a leak to ground (but that would produce heat somewhere). If the meter doesn't move, then measure the load on individual breakers. Look for large intermittent loads and see what they draw when running and estimate how often they are running.

Keep in mind that it may be more than one thing.

Good suggestions from everyone here.  Chances are good that you could point your infrared camera at the main panel and tell which circuits are warm and drawing a large amount of current.

I have found a waterlogged expansion tank for the well pump system numerous times. This could easily run the electric bill up with it's constant on/off cycling when water is drawn.  A leaky foot valve would also cause constant running.

If the clothes dryer is used a lot, how long does it run per load? 50 minutes is reasonable, 2 hours is not. Clean out the lint from the trap through the impeller fins and the length of the pie to the exhaust hood. I have found shorted elements in a clothes dryer, but that's a long shot.

I've run into shorted heating elements in water heaters which still delivers hot water, but is running current to ground 24/7.

A short cycling sump pump, hidden pipe heaters, roof eave heaters, and even "grow" closets can run up the electric bill.

An open loop geothermal system that has run dry could contribute to high bills, or strip heaters with a bypass duct may be the culprit.

Is the meter on a pole or on the house? If on a pole, then Brad's suggestion of underground leakage may be the issue.

A clamp-on Ammeter is going to be a useful tool here.  Current data loggers are next on the list if it isn't obvious.  

Lastly, but quite remotely, the meter is erroneous. This is more likely with a digital meter than with the older electro-mechanical ones.

Let us know what you find, it'll help all of us be better detectives.

Mr. Buchanan,

I also had a client with similar issues, though the rural home was not a working farm.The electric usage for the "polar vortex" month two years ago was 17,196 kwh. For the month. I found the heat load for the house greater than the ground source heat pump could handle. I provided the client with some project management to get a quality air sealing and insulation job in place, and we changed the thermostat on the heat pump to provide a 4 degree temperature difference before the resistance heat kicked in.

The key there was the blower door number, and the lack of insulation in the bonus room. Remember, heat goes to cold. The bonus room had been 15 to 20 degrees colder, and there was significant knee wall attic leakage.

My question for you has already been asked. What is that blower door number, and where are the leaks? Also, what is the size of the resistance heating elements in the heat pump? A corollary question, is there any additional heating for the house installed when the expansion took place? If not, why not? What was done more than doubled the size of the house, and could have had some effect on the heat load calculations...I think. It is possible the heat pump is simply too small for the house.

Let us know what you find out, sir, please. Oh, and the client I had told me there is only one degree of temperature difference in the bonus room from their dining room. I left them a temperature/relative humidity monitor to keep track of and document their comfort. Cost me ten bucks, and they love it.

Excellent suggestions provided by everyone here. @Brad Cook had the most useful info to offer, matching my methodology:

"To give some perspective, at 11,568 KwH per month, that would be 16.07 KwH per HOUR, or 67 AMPS at 240 VAC (134 amps at 120 VAC) running 24/7. Yes, that is HUGE for the situation described. Put an amp meter on those circuit breakers."

When a 5000 watt hot tub element runs it's pulling about 20 amps, which is about 30% of the total 67 amps Brad is referencing. If it runs 24/7 (which they never do), it would consume only 3600 kWh/month. So it's fairly safe to assume it's not the hot tub (although it could be a significant factor). 

And a 2 HP well pump running full bore consumes about 3100 watts. Running that 24/7 would amount to about 2232 kWh/month. So it's fairly safe to assume it's not the well pump (although it could be a significant factor).

A quick slam-dunk energy model for a 6000 sq-ft home (assuming 10 ft high ceilings, radiant floor, 6000 HDD/year, 800 sq-ft of windows, 0.4 ACHn, 300% HP efficiency) at http://www.builditsolar.com/References/Calculators/HeatLoss/HeatLos... results in the following:

132,400,000 BTUs/year with a 300% efficiency-rated ground-source heat pump equates to about 12933 kWh/year. If we assume something is wrong with the heat pump and it is using straight resistance heating elements (at 100% efficiency), then you would be looking at something like 38791 kWh/year, which is definitely something to look at. Is it glycol or water running through the ground loop? If it's water, is it leaking/being replaced by water pumped from the well? A check of the delta T between hot and cold sides of the ground loop would determine if this is so.

When was the ground-source heat pump installed? At the same time as the 3000 sq-ft addition? Was a new service and/or meter installed at the same time? Is it a digital model? If so, those suckers are sometimes bad and need to be tested with a third party meter that is UL listed (I highly recommend this one from EKM). Without a good third party tried and true meter, I believe you will be wasting your time. Digital meters (and/or the CTs that feed them) are sometimes bad, and when they are, they are sometimes REALLY bad. First check that. Then, if the values you collect from a week's worth of monitoring match the utility's values (mind the proper multiplier), you have good reason to dig deeper.

Good luck!

I've seen similar situations and it always comes down to either:

1 - a pump or motor that is stuck on for some reason (leak, faulty control), or needs to be on for some reason (GSHP, duck pond bubbler, recirc, HRV in the pool house)

2 - electric resistance heat that's either on (space heat or livestock water heater) or hidden. I once found electric radiant floor heat with my IR that was unknown to the owner, and unlabeled at the breaker box - it was pretty much on all the time.

Good Luck and let us know what you find!

I found a strip heater used in new work all hard wired up set at 55' in the attic on ply wood - when the attic got below 55' the 26 amp heater would turn on.   This made ice dams and the roof got replaced 6 times in 5 years.    I found this with a HOBO to the main then to branch lines till I found the right beaker.  My point is to test and prove what is going on.   Motors use the most power then strip heat.    

OK so we did the site visit yesterday, and this is the information relayed to me:

There are two GSHPs. One of them is not working and off. The other is on and running on aux heat, because the GSHP is not operating correctly. The customer advised that he had to manually, at the unit, turn on the aux heat.

The home went through CAP agency weatherization. Our agencies are exceptional, and the one that serves this area is one of the best, so there's no risk of shirking there. Home was tightened to below 62.2 standards, and required added ventilation.

They are currently running space heaters as needed, and there is resistance floor heat in some parts of the home. This accounts for the higher usage this winter, but not enough to represent the outlier usage last winter.

Our usage modeling software had their non-winter estimated usage in line with what their actual usage was, but winter was wonky. This, of course, points to the GSHP as the issue.

Now we come to brass tacks: When the GSHP was installed, it seems that it may have been by a, let's say, inexperienced installer. The customer had the installer out at least once. The installer did some triage and, of course, insisted that the problems would be solved. When they weren't, they (I think both the installer and customer) had the supplier come out as well. The supplier insisted they would take care of it and get it working correctly, no matter what. They changed out some components (again, triage) and insisted the problem would be solved. When it didn't, the customer claims the supplier reneged and said there was nothing they could do.

At this point, they had a more experienced installer come out and advised that the loops were likely in great shape. It is the indoor units that would take so much effort to repair that it would be more cost effective to replace them. 

We've also had the utility out to the site and there's nothing particularly funny about the setup before the meter.

All this, coupled with the non-heating months being pretty normal, lead us to believe that the issue is with the GSHP indoor units.

I do not have enough experience with them to make a solid recommendation to the customer for the next steps, beyond having someone competent in there to replace the indoor units. Do any of you have any experience with situations like this, and what are the possible solutions for the customer beyond just eating the cost of the new indoor units?

I would have bet a good amount of money it was the GSHP, as I've often seen they don't perform as advertised. Can you provide the make/model of the pumps so we can do a little research? Those things and their control systems can be a frightening black box that only a handful of people around the world know what to do with :p

I'm the most un-litigious guy around, but it sounds to me like the customer needs to spend their money on a good lawyer if the installer and supplier are unable to get the system to work. That's a huge investment that should perform as advertised, not multiply your bills by tenfold or more.


Latest Activity

Paul Raymer posted an event

Radon Protections in New Homes at On line

January 30, 2018 from 1pm to 2pm
Radon-resistant construction is becoming a focal point in the high performance building industry.…See More
11 hours ago
mark avila posted a discussion

Aeroseal Homeseal Pro unit for sale?

Hello,We may be in the market to purchase a used machine should someone have one for sale.Cordially,See More
13 hours ago
Robert Zockoff liked Tray Biasiolli's discussion Two-stage furnace, control at furnace or thermostat?
15 hours ago
Profile IconKevin Jacks, Christine Elovecky and Bryan McIntyre joined Home Energy Pros Forum
17 hours ago
Kevin Jacks liked Diane Chojnowski's group Job Board
17 hours ago
Scott Doyle liked David Butler's discussion RESNET gets serious about modeling platform consistency
18 hours ago
Quinn Korzeniecki posted an event

BPI Retreat at HPC New York 2018 at Saratoga Springs, NY

February 12, 2018 from 12pm to 4pm
BPI will be hosting a retreat for BPI GoldStar Contractors, Test Centers, Proctors, and Certified…See More
19 hours ago
Quinn Korzeniecki added a discussion to the group Building Performance Institute (BPI)

BPI to Host Retreat for Stakeholders on February 12th

BPI will be hosting a retreat for BPI GoldStar Contractors, Test Centers, Proctors, and Certified…See More
19 hours ago


  • Add Photos
  • View All

© 2018   Created by Home Performance Coalition (HPC)   Powered by

Badges  |  Report an Issue  |  Terms of Service