Excessive KW/hr

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mtnelectrical

Senior Member
I have a call from a customer saying he has been paying over $600 a month in electricity. They have a central air and the months of more usage were in summer. Funny thing, they say there is nobody during the day so AC is off but when they came back in the afternoon, becauce they want to cool the house "really fast" they put the tstat in 35 degress until it is cold "enough" and turned it off. Do you think this is the reason for the high bill? House is aprox 950 sq feet.
 

jumper

Senior Member
I have a call from a customer saying he has been paying over $600 a month in electricity. They have a central air and the months of more usage were in summer. Funny thing, they say there is nobody during the day so AC is off but when they came back in the afternoon, becauce they want to cool the house "really fast" they put the tstat in 35 degress until it is cold "enough" and turned it off. Do you think this is the reason for the high bill? House is aprox 950 sq feet.

T stat at 35 degrees? what the heck the unit would freeze up?
The compressor may be leaking to ground like WH can and drive bill up.
 
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ceb58

Senior Member
Location
Raeford, NC
I have a call from a customer saying he has been paying over $600 a month in electricity. They have a central air and the months of more usage were in summer. Funny thing, they say there is nobody during the day so AC is off but when they came back in the afternoon, becauce they want to cool the house "really fast" they put the tstat in 35 degress until it is cold "enough" and turned it off. Do you think this is the reason for the high bill? House is aprox 950 sq feet.

Could very well be. If the A/C is set to a temp and left alone the A/C would have less running time on it in a 24hr. period than doing what they are doing. But there are other factors that come into play, R rating of insulation, home sitting in full sun, etc......
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Thats a heck of a power bill for that small of a house! Surely it can't be that hot in NJ! I maybe see that with electric heat, Do they have any underground power to outbuildings? A well pump?
 

kwired

Electron manager
Location
NE Nebraska
Turning thermostat up or down will not make it get hot or cold faster, with exception of multistage unit, but changing the thermostat only 3 or 4 degrees will make unit run at full capacity. If you desire a 10 degree temperature change and re-adjust the thermostat after achieving the 10 degree change you still used the same amount of energy as if you just made a 10 degree change to the setting.

If the system is capable of cooling "really fast" it is most likely oversized and could be an energy hog to some degree, problem with oversized cooling units is they cool the space too quickly before humidity level is lowered and shut off. Because the humidity is still high the space is not comfortable. A properly sized two stage unit will run almost continuously on the hottest day it was designed for but on the low stage for most of this period.


question - does the unit have electric heat installed in it? If so make sure that there is not a control problem and the heat or even part of it is not operating while cooling. This would be counter productive and consume a lot of energy. I have run into a problem like this before - original installer incorrectly wired the thermostat on a new heat pump installation and it was heating and cooling at same time.
 

mtnelectrical

Senior Member
good points here, but there is no outside wiring or wire underground going somewhere, not well pump, this house is in the city, or sump pumps. Heating is gas and it is not working at the same time. And yes I have already explained to the owner that setting the tstat to very low temperature will not cool faster.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
100429-2231 EST

Put some instrumentation on this house and see what the data is. Some quick tests should tell you a lot.

If you do not make some of your own measurements, then it is a total guessing game and not very efficient.

.
 

kwired

Electron manager
Location
NE Nebraska
Electric or gas water heater? How about hot tub, swimming pool, do people take long showers frequent baths, how much time is put on laundry equipment especially an electric clothes dryer. Leaking hot water faucets?
Is air conditioning in properly maintained condition and operating efficiently? How many people live in this house?

Could be combination of things contributing to high bill especially if it did not suddenly increase.

With that kind of bill it should not be too hard to find something that is drawing more power than maybe expected.

You did not say if bill suddenly increased to the $600 level or if it has always been high for them. They may use more than they realize.
 

hurk27

Senior Member
good points here, but there is no outside wiring or wire underground going somewhere, not well pump, this house is in the city, or sump pumps. Heating is gas and it is not working at the same time. And yes I have already explained to the owner that setting the tstat to very low temperature will not cool faster.

I always use a car as a way to get a home owner to understand changing the temperature setting allot is wasting energy,

a car uses the most energy accelerating up to speed, while it uses the least when it just has to maintain the speed, this is why the cruse control achieves the best gas mileage in most cases, and a person who changes speed allot will get the worst gas mileage.

If your changing your temperature setting allot you will use much more energy then if you set it and forget it, even just a few degrees change can have a dramatic effect on your bill, turning off the system completely then trying to turn the system back on every day especially after the day sun has heated the house up will even make it more costly.

What most people don't realize is your not just changing the air temperature, but also changing the temperature of all the mass in the controlled area, walls, furniture, floors, every thing , also by allowing the controlled area to become humid adds the mass of the moisture in the air to the load until it can be removed again, we call this "removing the heat content" In my house I have found through some test that unless I'm going to be gone more then 3 days it is not cost effective to touch the temperature setting, and even then I only would raise it a few degrees. and when I return I wait until the sun has long set before I even try to lower it.

There have been studies that has shown that these programmable stats have cost home owners much more in lost energy then they save because people was trying to change the temps too much and or too often (I got rid of mine)

Our utility is among some of the highest in the country for electricity, (.16 cent per KWH) so it was a big thing for me to find that sweet spot when it came to air conditioning settings as it didn't take much to cause my electric bill to jump when messing with the temp settings.

But as others have said, to know where all the watts are going would take a total study to get a picture of the whole, as there are many things that can cause high electric bills, we get these request allot around here just because of our high electric rates.
 

DavidA

Member
Location
Fresno, CA
If nothing else, perhaps you can sell them on getting a programmable T-stat. They don't have a new 'smart' meter by any chance, do they?
 

Chamuit

Grumpy Old Man
Location
Texas
Occupation
Electrician
Is the POCO meter digital or analogue? Can you turn everything off and see if the meter is still turning?

What I am getting at is like when you have a water leak. Turn all water off in the house and see if water meter is still running. Slab leaks, service line leaks, etc.

Wonder if someone is siphoning electricity, or there is a fault as someone else noted earlier.
 

SAC

Senior Member
Location
Massachusetts
There have been studies that has shown that these programmable stats have cost home owners much more in lost energy then they save because people was trying to change the temps too much and or too often

Any references? It is well known that using programmable thermostats with a setback can save energy. The reason is that the rate a house looses heat (or gains heat) is roughly proportional to the difference between the inside and outside temperature. So when the house temperature is much hotter or cooler than outside it takes more energy to maintain it there than if it was closer to the outside temp. A good rule of thumb I've heard is to use a setback if the setback period is long enough that the house reaches a constant temperature before the setback period ends. The longer the constant temperature during the setback, the more energy saved. If it doesn't reach a constant temperature, it isn't really saving energy because roughly the same energy saved when the house is approaching the setback temperature is lost to return the house back to the occupied temperature.

For example:

http://www.homeenergy.org/article_full.php?id=566
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
100430-1725 EST

Some specific suggestions:

Look at the electric bills over some period that includes a period when the bill was reasonable. Study and understand anything special about how rates vary as a function of usage. Calculate the average cost per KWH for one year, maybe from your own bill and the customer's. If these averages differ substantially, then find out why. Divide the customer's average cost per KWH into $600. Does the number of KWH listed on the bill agree approximately with your calculated value? A large disparity may indicate a billing problem.

As was previously mentioned open the main disconnect. Does the meter rotate? It should be perfectly still. Next turn the main back on and turn off all but one circuit that has an outlet that you can plug a 1500 W heater into. Turn off anything on this one powered circuit. The watthour meter should not be rotating. If this is the case, then plug the heater in on maximum power and with its thermostat set at maximum temperature so that heater remains on continuously. For exactly 5 minutes, try 1 minute first, count the number of revolutions of the watthour meter. Figure out the calibration of the meter, KWH per revolution. Now you can do a calculation to see if the meter corresponds with the actual load. A heater I have reads 1410 W at 118.1 V and thus its hot resistance is 9.89 ohms.

If it appears the KWH meter is correctly calibrated, then turn all circuits on. Obviously disconnect the 1500 W heater.

It would be preferred that you have a two channel recording wattmeter. If not you do your best with other instruments. Connect the recording wattmeter to monitor both hot service entrance wires. See what your readings are. Assuming no electric water heater or furnace, then you might expect the power load to range from 500 to 2000 W with someone in the house doing normal activities. It will be higher if an electric stove or iron is on. In my house which is substantially larger than the one you describe my average daily use is in the range of 28 to 40 KWH/day. I only achieve 28 by working hard to keep things off that are not needed. My cost average per year is about 13.7 cents per KWH or per day at 40 KWH about $5.50/day or for 31 days $170/month.

At night my consumption drops to about 600 W average for 1 refrigerator, 2 freezers, and furnace fan motor plus some small loads. About 5 KWH total for the night hours. This is without going back and looking at precise data.

At 40 KWH/day the average power consumption is 40/24 = 1666 W.

If you see excessive power consumption under normal conditions, then start looking for the circuit or circuits responsible by selectively turning off breakers.

If under normal conditions and the KWH meter calibration is OK, and you see nothing abnormal, then you need a power recording instrument to see what happens vs time.

To do initial rough checks for power consumption you can use a single clamp on ammeter and look for causes of high current. 500 W is about 4.2 A .

.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Meter brake test

Meter brake test

You may want to do a quick meter brake test.

Turn off all loads but one big one. I use the oven.

Watch how the meter spins down as someone clicks the load off. The disc should stop instantly. If it slowly spins to a stop, the brake is bad and the customer is being charged for energy they are not using.

If your brake test fails, it's time to call the POCO for a new meter and a possible refund for the customer.

Brake failure is rare, but it does happen.
 

mtnelectrical

Senior Member
I checked other things, found air handler running amps 7.8 amps,( I think kind of high) The meters are analog This is 2 familiy house in with no too much space in the backyard so no swimmin pool, or jacuzzis, basic house, 5 years old so I guess well insulated this is 1st floor apartment theres is a finish basement that is part of the first floor. I will check the braking of the meter and I already turned the main off and no movement of dial. Lets see what I found, my guts are they weren't using the thermostat properly. They even have that air handler running manua and not in auto with the unit, when cold or hot is called and it is the only time that the fan is working.
 

kingpb

Senior Member
Location
SE USA as far as you can go
Occupation
Engineer, Registered
I'd say something odd is a drift. I live in Florida, and my combined elec, water, sewer and trash is half that amount in the peak of summer, and I got 4-kids.

You say apartment? Reminds me of the extension cord plugged into the neighbors outlet story.

Sure they arn't growing weed:grin:
 

MJJBEE

Member
Was this just a single indecent? I have seen it where the meter reader marked the wrong reading into their program. if that is the case you can call the utility and have your meter checked out and re read. Also they could have a meter issue they are more common then you think.
 
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