Author Topic: My power consumption has almost tripled last month - advice please  (Read 3807 times)

kms

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Something odd has happened. On June 6th 2018 I've had a brand-new A/C unit installed, coil and external fan, because the old one was 15 years old, leaking, incapable of keeping the house cool (it warmed up to 87F in the afternoon) and rather inefficient to boot (like I said: 15 year old original unit, certainly not the most high-quality A/C made). However, in the last month between 6/1 and 7/2 my power consumption has almost tripled. Yes, June was hotter than May here in Austin but not that much hotter. May was pretty bad already. Plus, my power consumption is more than twice as high as it was in September last year when we moved into this house, and September 2017 was a very hot month as well.

Here are the numbers for the last few months:

03/2018: 400 kWh
04/2018: 335 kWh
05/2018: 469 kWh
06/2018: 1,174 kWh

Last years high was would have been 870 kWh in August, but since we only moved in in mid August we only paid for half the month, aka 435 kWh between 8/15/17 and 9/1/17. And that was with the old A/C running on full blast as it was already leaking and sort of broken. The new unit was supposed to be more efficient I was told..

I keep thinking what might have changed in the last month, and the only three things I can think of are:

* new A/C (coil & outside fan) on 6/6/18, installed by professionals
* new ceiling fan and light in the office on 6/10/18, installed by myself
* new power supply for a computer in late May after the old one failed

I haven't touched the thermostat, it is still set to 78F during the day and 82F at night (basically shutting the A/C unit off at night). One thing I've noticed is that whenever the A/C fan is running I can hear the furnace in the attic. Not sure whether or not that's expected, and I can't really tell whether or not it was doing that before as I haven't checked or noticed. I've noticed it by accident this time because I was up in the attic once when suddenly the fan kicked in and the furnace started going bananas.

I'm having the company that installed the new A/C last month come over and check, is there anything else I can do to find out what's going on?
« Last Edit: July 09, 2018, 05:23:26 PM by kms »

red_pill

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Re: My power consumption has almost tripled last month - advice please
« Reply #1 on: July 09, 2018, 07:59:22 PM »
Our furnace fan runs when the a/c is on also.  But thatís because that is what circulates the air.  Itís not the actual furnace (no hot air), itís just the furnace fan running.  That runs at about 300 Watts for us, and it should only be running when the a/c is on - not continuously.

Linea_Norway

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Re: My power consumption has almost tripled last month - advice please
« Reply #2 on: July 10, 2018, 02:12:35 AM »
I think you should start reading off your electricity on a daily basis and switch off one of the named devices every alternate day to see which one makes a difference.

Are you sure your thermostat turns off you AC?

Could you have some devices doing the opposite? Like the new owner of our previous house who was having a fire in the wood stove, while the warmth pump was set to cooling the house down and running at full power. Now this person was not familiar with how the warmth pump worked. But could your central heating be trying to get the house on the temperature that the thermostat shows, while the AC is trying to cool it down?

I suppose no one from outside has somehow started to use your electricity?

Maybe your old AC unit was working so badly that it didn't use all it's capacity? If you calculate the difference between having the AC on and off, can you then calculate if that is normal use the for new unit?

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #3 on: July 10, 2018, 08:04:00 AM »
Thank you so much both of you for your advice.

Our furnace fan runs when the a/c is on also.  But thatís because that is what circulates the air.  Itís not the actual furnace (no hot air), itís just the furnace fan running.  That runs at about 300 Watts for us, and it should only be running when the a/c is on - not continuously.
OK, that's what I sorta figured already, thank you. It is definitely not heating the house - I would have noticed that on our gas bill, which was pretty much NIL hast month. It is definitely not running 24/7, I already made sure of that. But thanks for reassuring me that it is in fact expected behavior.

I think you should start reading off your electricity on a daily basis and switch off one of the named devices every alternate day to see which one makes a difference.
I thought about that too, but have you ever tried turning off the A/C in central Texas between March and November? The house would heat up to more than 40-45įC within an hour or two. What I can do is turn off the PC and the light/fan in the office for 24 hours and see if they make a difference.

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Are you sure your thermostat turns off you AC?
Yes, I can hear it turning on and off regularly during the day and less frequently in the evenings.

Quote
Could you have some devices doing the opposite? Like the new owner of our previous house who was having a fire in the wood stove, while the warmth pump was set to cooling the house down and running at full power. Now this person was not familiar with how the warmth pump worked. But could your central heating be trying to get the house on the temperature that the thermostat shows, while the AC is trying to cool it down?
While that would be possible in theory I don't think the current thermostat supports this. I have to actively set a switch to either "Cool" (left), "Heat" (right), of "Off" (middle), and I have a gas furnace in this house. Last month's gas bill was $3, which accounts for cooking and hot water, so I don't think that's the problem. I was considering something along these lines as main culprit as well.

Quote
I suppose no one from outside has somehow started to use your electricity?
That I can definitely rule out, yes.

Quote
Maybe your old AC unit was working so badly that it didn't use all it's capacity? If you calculate the difference between having the AC on and off, can you then calculate if that is normal use the for new unit?
I would if I could turn the A/C off but like I said: given the current outside temperatures I'd be boiling within less than two hours. It'll be late October / early November until I can safely turn the A/C off for more than a couple of hours. Also, as far as I'm informed that's not how A/C units work. The old unit was practically running 24/7 because the thermostat was set to 78F but the house was constantly at more than 80F. Accordingly, the A/C and fan were on all the time.

I did take notes of the power meter reading since last night, and apparently whole house consumption between last night, 6pm, and this morning, 6:15am, was 10 kWh, or 0.82 kW/h. I did, however, remember that I changed one setting on the thermostat at some point last month shortly after the new A/C unit was installed: instead of "Hold 78" I set a schedule for different temperatures during day and night. I have just reset this to "Hold 78" again and am going to keep my eye on the power meter. We've already consumed 229 kWh in the last 7 days, or 32,8 kWh/day, since the last reading. I'll see if that thermostat settings makes a difference or not in the next few days.

FIRE@50

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Re: My power consumption has almost tripled last month - advice please
« Reply #4 on: July 10, 2018, 08:12:23 AM »
Are you getting the kWh values from reading the meter yourself or are those values coming from your electric bill? Is it possible that this is just a billing error?

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #5 on: July 10, 2018, 08:19:45 AM »
I'm getting them straight from the meter, and they match the numbers on the bill.

steviesterno

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Re: My power consumption has almost tripled last month - advice please
« Reply #6 on: July 10, 2018, 08:30:40 AM »
on of the things we did (Dallas, so I hear ya) is utilize window units in the bedrooms we actually use. this allows us to turn down central air in the rest of the house. We keep it cooler since my wife works from home and we have a toddler, but we saved a bunch of money by only cooling the rooms we are in at night and the rest of the house when needed.

not sure if that helps you, but it may be an option.

On thing to look at is the power of your AC unit. if you had a low rated one 15 years ago (rated in seers or sears, I'm only a bit familiar) and then jumped into a way more powerful version, that may be the culprit.

My AC bill is about $300 this month, but since we don't use heat in the winter and those bills are like $80 it cancels out. I'm not rich but I'm rich enough to not sweat myself to sleep anymore.

dcheesi

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Re: My power consumption has almost tripled last month - advice please
« Reply #7 on: July 10, 2018, 08:41:10 AM »
I had a weird issue where my bill went up like that, even though I hadn't changed anything at all. It turns out that a control relay had gone bad in my A/C system, with the bizarre effect being that every time my system fan was running, my auxiliary heating coils[1] were powered up as well?!

So every time my AC tried to cool the place down, it was fighting my emergency-heating system trying to warm it up. Even worse, for the first month I was running the fan 24/7 to help circulate air between floors of my home, so I was effectively running a large space-heater constantly during the hottest days of summer!


[1 all-electric heat pump system. I suppose the equivalent for you would be your furnace, which is part of what made me think of this incident]

Proud Foot

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Re: My power consumption has almost tripled last month - advice please
« Reply #8 on: July 10, 2018, 08:57:44 AM »
Does your electric company actually read the meter every month for billing? Or do they do an estimate and check quarterly and adjust your bill to reflect actual usage over the quarter? If this is the case it could be you had a high usage month before getting the AC switched and it is only now reflected on this bill.


kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #9 on: July 10, 2018, 09:50:37 AM »
On thing to look at is the power of your AC unit. if you had a low rated one 15 years ago (rated in seers or sears, I'm only a bit familiar) and then jumped into a way more powerful version, that may be the culprit.

My AC bill is about $300 this month, but since we don't use heat in the winter and those bills are like $80 it cancels out. I'm not rich but I'm rich enough to not sweat myself to sleep anymore.
That was one of the first things I checked right after the company installed the new unit. It's supposed to be as powerful as the old one but more efficient. I've just checked the new unit, its SEER rating is 14 with an asterisk that says it may be more efficient depending on coil. Unfortunately, I don't have the documentation for the old one and forgot to take a photo of the label. However, I trust the contractor as he's replaced several units in this neighborhood and has an impeccable reputation. Our AC bill this month would have been more than $220 for a 1,700 sqft single story house with a single unit, but the solar panels produced $85 worth of electricity so we're down to $135. Still, the month before our bill was $8, and we even made $25 in the month of April. Plus, we were told by the previous owners of this house that they never paid anything for electricity.

I had a weird issue where my bill went up like that, even though I hadn't changed anything at all. It turns out that a control relay had gone bad in my A/C system, with the bizarre effect being that every time my system fan was running, my auxiliary heating coils[1] were powered up as well?!

So every time my AC tried to cool the place down, it was fighting my emergency-heating system trying to warm it up. Even worse, for the first month I was running the fan 24/7 to help circulate air between floors of my home, so I was effectively running a large space-heater constantly during the hottest days of summer!
This is brilliant, thank you! I'll make sure to mention this to the technician when he comes over either today or tomorrow.

Does your electric company actually read the meter every month for billing? Or do they do an estimate and check quarterly and adjust your bill to reflect actual usage over the quarter? If this is the case it could be you had a high usage month before getting the AC switched and it is only now reflected on this bill.
It's a smart meter so they actually read it every month. A previous owner installed these new meters when they installed the solar panels on the roof.
« Last Edit: July 10, 2018, 09:56:04 AM by kms »

Retire-Canada

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Re: My power consumption has almost tripled last month - advice please
« Reply #10 on: July 10, 2018, 10:17:34 AM »
I keep thinking what might have changed in the last month, and the only three things I can think of are:

#1 * new A/C (coil & outside fan) on 6/6/18, installed by professionals
#2 * new ceiling fan and light in the office on 6/10/18, installed by myself
#3 * new power supply for a computer in late May after the old one failed

I'm having the company that installed the new A/C last month come over and check, is there anything else I can do to find out what's going on?

You could monitor daily power usage then disconnect #2 and #3. Monitor for a couple days and see if anything changes significantly. If not you can rule them out.




SimpleCycle

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Re: My power consumption has almost tripled last month - advice please
« Reply #11 on: July 10, 2018, 11:52:24 AM »
How big is your place?  Did the new A/C also mean a change in thermostat to a smart thermostat?

If you have a smart thermostat, I would check all the settings to make sure the "run fan X minutes every hour" is not set to something wild.  Our electricity consumption went up a bit in the winter with our smart thermostat because we run the fan for 10 minutes every hour to circulate the warm air in the system.

But that said, I suspect the answer is your old A/C was broken in a way that made it consume less power because it wasn't working correctly.  Your current usage looks right to me for a house running a substantial amount of A/C, depending on size.  I live in Chicago (so hot but not wildly hot summers) and our usage in the summer is right around 700 kwh for a 1200 square foot condo.  Our A/C usage adds about 400 kwh to our baseline electricity usage.

bacchi

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Re: My power consumption has almost tripled last month - advice please
« Reply #12 on: July 10, 2018, 12:49:56 PM »
How big is your place?  Did the new A/C also mean a change in thermostat to a smart thermostat?

If you have a smart thermostat, I would check all the settings to make sure the "run fan X minutes every hour" is not set to something wild.  Our electricity consumption went up a bit in the winter with our smart thermostat because we run the fan for 10 minutes every hour to circulate the warm air in the system.

But that said, I suspect the answer is your old A/C was broken in a way that made it consume less power because it wasn't working correctly.  Your current usage looks right to me for a house running a substantial amount of A/C, depending on size.  I live in Chicago (so hot but not wildly hot summers) and our usage in the summer is right around 700 kwh for a 1200 square foot condo.  Our A/C usage adds about 400 kwh to our baseline electricity usage.

This is probably why. The old AC struggled to keep the temp at 87. You're cooling it 9 more degrees to 78.

How big is the house, OP? And is it well insulated?

Takk

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Re: My power consumption has almost tripled last month - advice please
« Reply #13 on: July 10, 2018, 01:55:49 PM »
June 2018 was on average 3 degrees higher than August of 2017 according to the weather sites in Austin Tx. Take that as you will.

There is also to confirm the AC is working right, run a clamp amp meter on it. confirm it's within specs, from there it's just making sure the unit has the correct amount of refrigerant and is controlled properly.

Also check to see if you're conditioning the attic on accident, holes or misconnections etc in ductwork from them working near it.

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #14 on: July 10, 2018, 02:34:16 PM »
The thermostat has not been replaced, and it's still the same old Honeywell 97-5110 that this house came with when we bought it. From what I saw in neighbor's houses it's probably the original one from back when this house was built in 2004. It's anything but smart and can only run two programs: hold temperature and timed temperature (four settings for weekdays, two for weekends).

The house is a 1,700 sqft single story 3/2 with a single A/C unit. It is not insulated particularly well as insulation is very uncommon in Texas. I will definitely look into that in the long run and make sure the windows and doors are properly insulated but none of the previous owners seemed to have cared.

Thanks for the suggestions on how to test whether the AC is working correctly. I'll talk to the A/C technician once he's here to check the system. The attic seems fine, I was up there yesterday and it was just as hot as it always was. No cold air getting in there for sure. Although I did notice that one of the two window fans was not spinning. I should probably look into that as well.

zolotiyeruki

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Re: My power consumption has almost tripled last month - advice please
« Reply #15 on: July 10, 2018, 02:44:33 PM »
That amount of electricity doesn't sound unreasonable.  I used to live in Houston in a similarly-sized house.  Our summer consumption was consistently over 1000kWh per month, and that was with a new (installed while we lived there) 13 or 14 SEER unit.

KCM5

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Re: My power consumption has almost tripled last month - advice please
« Reply #16 on: July 10, 2018, 03:19:20 PM »
Seems reasonable to me, too. Iím 1,000 miles north of you, in a smaller, presumably better insulated house, granted with an older AC unit, keep my air at 78-80, and have had months where we use over 1,000 kWh. Our baseline in spring and fall with no heat/ac/fans in about 300 kWh.

I think you may just be experiencing your first full summer in your new house! It is surprising that the old owners said they never paid electricity. How much electricity do your solar panels produce? Do you have to clean them off or anything (I dont have solar panels and donít know if this helps!)

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #17 on: July 10, 2018, 05:47:30 PM »
There's some more news. I've talked to a neighbor, the same that installed the solar panels about two years ago, since he offered to take a look a my bill to make sure everything was in order. And I finally understand the bill now.

First, the bad news. My power consumption last month (between 6/1 and 7/2) was not 1,147 kWh but 1,980 kWh due to the way the City of Austin (the sole provider of electricity in this area) does the billing. The system was installed back when the old billing was still in place, where they actually ran net meters. Meaning: whatever I produced I consumed, and the rest was billed. Now, the meters still reflect this net billing but the actual billing is different, and the actual amount of electricity consumed last month equals whatever I produced plus whatever I pulled from the grid minus the overproduction. For last month, these are:

Received from the grid: 1,174 kWh
Delivered to the grid: 126 kWh
Net received from the grid: 1,047 kWh
Produced by PV: 861 kWh
Whole house consumption for the month of June equals net received + produced by PV = 1,980 kWh.

Looking at my previous bills that is still more than twice as much as before.

03/2018: 645 kWh (produced: 778 kWh)
04/2018: 576 kWh (produced: 770 kWh)
05/2018: 886 kWh (produced: 864 kWh)
06/2018: 1,980 kWh (produced: 861 kWh)

In other words: while 1,000 kWh may seem realistic for a summer month in central Texas 2,000 kWh certainly aren't.

The other piece of news is that under the old billing system (the net billing), our bill would have been around $30 lower because we would have not been billed and then reimbursed for the 861 kWh we produced. They would have simply been subtracted from whatever we received from the grid, and we wouldn't have had to pay regulatory charges, community benefit charges, and power supply adjustment summer for the whole 1,980 kWh but just 1,047 kWh instead.

Either way: our power consumption is still too high, and I'm now actively looking into it. I'm writing down the meter readings several times a day and am trying to get a rough estimate of daily consumption so I can try out a few things.

the_fixer

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Re: My power consumption has almost tripled last month - advice please
« Reply #18 on: July 11, 2018, 07:39:48 AM »
Is it possible that the old AC unit had a savers switch that the technician removed or did not replace?

Not sure if it is called the same thing everywhere but it is a device that the eletric company installs that allows them to control your AC to some extent to save energy at peak times.

https://www.xcelenergy.com/programs_and_rebates/residential_programs_and_rebates/home_energy_efficiency/savers_switch

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Lulee

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Re: My power consumption has almost tripled last month - advice please
« Reply #19 on: July 12, 2018, 09:55:18 PM »
Not sure it's worth the money but Ask This Old House had a part by Ross Trethewey (https://www.thisoldhouse.com/how-to/future-house-smarter-home-electrical-metering) about a company making a super cool meter that learns about what's in your house and gives you real time info.  If it works like what they showed Ross, it's way cool and would be really helpful in your investigations to see what's sucking up all that juice --- maybe something else is crapping out on you like your fridge and it's just a coincidence that it's failing after your AC was replaced.

I checked and it's for sale now at https://sense.com/ for about $300.  Electricity is uber expensive in NH so if it's the same in Austin, you might get your money back by resolving the issue quickly this summer than say what it may take you with a Kill-A-Watt type meter that you plug into various appliances and track for a while to see what each one is using.  Unless, of course, your tech finds something wrong when he comes back which would be awesome.

Looking forward to hearing what the resolution turns out to be.

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #20 on: July 13, 2018, 01:27:05 PM »
Thanks for the tips. I've talked to the City of Austin and they said that my "daily reads for the bill cycle 06/01/18 to 07/02/18 are in line with the external temperatures for the time period." I've also talked to neighbors and their power consumption was also higher than usual in the month of June.

However, none of them experienced the 2.5x surge I have, and I'm still investigating. My main suspect right now is the thermostat, and I think it might be defective somehow. I've had it set on a timer for the month of June - 78F during the day (I work from home), 82F at night. The 78F is what might have caused the high bill - the A/C was running pretty much all the time with the thermostat set to 78F. Now that I set it to "HOLD 80" during the day, my power consumption went down by roughly 30-40%, from 37.8 kWh daily average in June to 22-27 kWh daily average over the last four days. I've had the thermostat set to 78F before the A/C unit was replaced and it was running all the time back then as well. I just figured that was because of the fact that it was unable to keep the house cold and inside temperatures were almost always above 78F.

Can a thermostat be incompatible with a new A/C unit? It's still the original thermostat back from when this house was first built 14 years ago. Or could it possibly be broken and is there a way to test it? It is set to 80F right now but it feels much cooler than 80F in here. Could it be that the thermostat thinks it's much hotter than it really is, and therefore runs the A/C more often than necessary?

Forgive me if those seem like stupid questions but I grew up in Europe where nobody had an A/C. My knowledge is thus very limited.
« Last Edit: July 13, 2018, 01:42:57 PM by kms »

zolotiyeruki

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Re: My power consumption has almost tripled last month - advice please
« Reply #21 on: July 13, 2018, 01:55:17 PM »
Can a thermostat be incompatible with a new A/C unit? It's still the original thermostat back from when this house was first built 14 years ago. Or could it possibly be broken and is there a way to test it? It is set to 80F right now but it feels much cooler than 80F in here. Could it be that the thermostat thinks it's much hotter than it really is, and therefore runs the A/C more often than necessary?

Thermostats are pretty simple devices.  They sense the temperature, and if it's above X, it sends 24VAC to the A/C compressor relay and the blower relay.  That's about it, for A/C.  For heat, it's the same deal, except it sends 24VAC to the furnace instead of the A/C compressor when the temperature drops below the setpoint.  Programmable thermostats work the same way, except they change the set point at various times throughout the day.

Your power consumption is going to be strongly correlated to the difference in temperature between the inside of the house and the outside.  It doesn't surprise me that your consumption went down 30% with the change you made.  Before, your A/C basically didn't run at night because of the cooler night air.  If you have it set at a constant 80 degrees, it will still run only a little bit at night.  During the day however, is where the difference probably is.  Before, your house was at 80 or 82 first thing in the morning, so the A/C had to cool the whole house down to 78, and then maintain that difference in temperature.  Now, it doesn't have to cool down the house first thing in the morning--it just waits for the sun and warmer air to heat your house, and then it has to maintain a smaller temperature difference.

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #22 on: July 13, 2018, 02:40:43 PM »
Interesting. That made a lot of sense, thank you!

Does that mean that I might be better off to leave the temperature at 80 day and night instead of, say, 80 during the day and 82 at night? Outside temperatures drop to around 75-80F at night around here, which means that when set to HOLD80 it is still running fairly often. I've had it set to 82F last night and it remained off most of the time and took around 10 minutes to cool down the house from 82F to 80F in the morning. We both get up at 5:45am so cooling down the house at this ungodly hour shouldn't take too long I guess.

grundomatic

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Re: My power consumption has almost tripled last month - advice please
« Reply #23 on: July 13, 2018, 03:08:47 PM »
Have you read all the MMM articles about efficiency? I blew insulation into my attic not long after buying my house earlier this year, only wish I had blown more in there. The related article:

http://www.mrmoneymustache.com/2014/05/01/beating-the-stock-market-with-diy-insulation/

There is also a very good one from early on in the blog:

http://www.mrmoneymustache.com/2011/09/01/what-is-thermal-mass-and-how-can-it-make-you-money/

...even when it was too hot to open up the house I night I've been known to make it COLDER at night to cool down my house when I am working against a smaller delta in temperatures, then increase the temperature one degree per hour until I can't stand it, then make it slightly cooler than that.

FWIW, I was at 884kWh for June in Tucson, AZ. My house is 1300sqft, one story, decent insulation (what I blew into the attic, thin insulation and stucco on the masonry, and new windows that came with the house), and two holes in the wall where my water heater lives in a room that doesn't get closed for reasons I don't want to talk about. In the spring I was in the 300kWh range, so proportionally my bill has gone up about like yours has.

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #24 on: July 13, 2018, 05:54:24 PM »
There's practically no insulation in the attic. It heats up to uncomfortable levels of heat in the summer, and I know I need to address this. We've only moved here less than a year ago, and attic insulation is definitely very high on my to-do list for this house. Simply haven't gotten around to it yet.

letired

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Re: My power consumption has almost tripled last month - advice please
« Reply #25 on: July 13, 2018, 06:25:51 PM »
Also a TX person:

+1 insulation! I have some but not a ton of insulation in my attic and I think it makes a big difference. The attic is still blazing in the summer, but it keeps the rest of the house ok.

For comparison, I used 513kwh between 5/14 and 6/14 to cool a ~1300sqft house to 80*F 24/7 with poorly sealed windows but some attic insulation, 0 wall insulation (block house), and decent afternoon shade.

diapasoun

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Re: My power consumption has almost tripled last month - advice please
« Reply #26 on: July 13, 2018, 10:18:09 PM »
Maybe not helpful for you at this point, but for posterity's sake: many energy companies allow you to model your usage online. When we had a big energy bill surge, we were able to look at the hourly usage patterns and figure out the cause based on that.

Also, for those who are worried about electricity usage in typical plug in appliances, a kill-a-watt would help!

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #27 on: July 19, 2018, 12:56:22 PM »
I've been doing a lot of research and writing down meter readings over the last couple of days, and I'm starting to accept the fact that what I'm seeing is absolutely normal for this street and Texas summers. It's our first full summer in this house (or any house for that matter) so we had no idea what to expect. I've talked to all my neighbors in the street and we're still the ones with the lowest power consumption by far. When I talked to one of them today she was shocked that our bill would only have been $220 if not for the solar panels. They've got a brand-new AC installed last year and are now only paying $350 per month whereas before they were paying over $500 in the summer months. Granted, they have a much bigger 2,500 sqft two-story house whereas ours is a 1,700 sqft single-story house, and she's got her A/C set to 74F whereas mine was set to 78F and is now on 80F.

There is no shade on our house at no point during the day whatsoever. Thus, it gets the full brunt of the Texas summer sun all day long, pretty much from 9am to sundown around 8pm. The A/C is running between 11 and 13 hours a day to keep the house cool, according to the usage stats. By changing the thermostat from 78d/82n to hld80 I was able to reduce average daily power consumption from 37.9 kWh in June to 28.5 kWh over the last 10 days, a 25% decrease. The last few days were higher than the first few days but it also got even hotter than before (between 105-110 each day now whereas we were in the mid 90s last week). I still believe the thermostat is somehow defective (or not working properly, or maybe simply old). I was taking laps with a stopwatch today, and in the late morning it was going through 2-4 full cycles per hour with 10-12 minutes off and 10-12 minutes on. Now, with the heat at its peak in the early afternoon, the A/C is off for 5 minutes and then running for 25 minutes even though it did not heat up significantly (or even noticeably) in these 5 minutes of off time. I have no idea whether or not that's normal but again, from what I was able to research it's not unusual for an A/C unit to run for up to 13 hours a day in the months of June-September around here.

I've just ordered a Nest thermostat for $211 (and will be getting $110 back from the CoA) and will see whether it'll make a difference compared to the almost crude 14-year old programmable thermostat that came with the house.

letired

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Re: My power consumption has almost tripled last month - advice please
« Reply #28 on: July 19, 2018, 03:21:49 PM »
I was about to suggest getting some shade trees, even if it's a long-term solution, but then realized it might fuck up your solar panel situation. I've never investigated how to balance solar productivity with heat-mitigation. Maybe those window films that are supposed to reduce solar gain?

bacchi

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Re: My power consumption has almost tripled last month - advice please
« Reply #29 on: July 19, 2018, 03:49:01 PM »
I was about to suggest getting some shade trees, even if it's a long-term solution, but then realized it might fuck up your solar panel situation. I've never investigated how to balance solar productivity with heat-mitigation. Maybe those window films that are supposed to reduce solar gain?

Or solar screens. You can build them yourself with a kit from Big Box. Well worth it.

Cranky

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Re: My power consumption has almost tripled last month - advice please
« Reply #30 on: July 19, 2018, 04:00:04 PM »
Frankly, my electric usage triples when I turn on the a/c. My unit is old and cranky and probably not all that efficient, but we have a relatively short cooling season in NE Ohio and it would take many, many years for a replacement system to pay for itself.

Texas, I think you're doing well if it's not a bazillion dollars/month.

letired

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Re: My power consumption has almost tripled last month - advice please
« Reply #31 on: July 19, 2018, 04:58:13 PM »
I was about to suggest getting some shade trees, even if it's a long-term solution, but then realized it might fuck up your solar panel situation. I've never investigated how to balance solar productivity with heat-mitigation. Maybe those window films that are supposed to reduce solar gain?

Or solar screens. You can build them yourself with a kit from Big Box. Well worth it.

Very good point! also shorter plantings around the house that will shade the walls but not the roof! Shrubberies, pruned fruit trees, vines on trellises, etc.

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #32 on: July 19, 2018, 06:53:44 PM »
While I love the idea of shrubs the house is built on a slope, and the South-West facing side that gets most of the sun over the course of the day is somewhere between 1.5 and 2 stories up so shrubs won't help. And I can't plant any trees on that side either for two reasons: a) at no more than 3-3.5 ft the side yard is too narrow, and b) they would be too close to the house allowing squirrels and, as I call them, tree rats to infest the house and use it for storage. My house is the last one on the far left, and as you can see there is literally no space for trees on the South-Western side of the house. Plus, planting trees there would most likely interfere with the solar panels eventually.

Solar screens are also a great idea but I already have blinds in every single window but one, and they're closed 24/7. I think the only thing I can really do is roof insulation. The way the house is built there isn't really much else I can do for extra shade.

I think I'm pretty much ready to accept that last month's power consumption was in fact normal given the circumstances. After all, everybody keeps telling me so...
« Last Edit: July 19, 2018, 07:10:22 PM by kms »

Gremlin

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Re: My power consumption has almost tripled last month - advice please
« Reply #33 on: July 20, 2018, 03:48:19 AM »
Absolutely consider insulation.  It's almost certainly your best bang for buck.

Have you also thought about sticking some more solar panels up there?  You've got plenty of free roof space from the pic.  Of course, it's hard to tell whether the panels would be visible from the street and impact the amenity of your house.

We had panels installed across our northern roof space (southern hemisphere so everything's reversed) and the panels themselves cut out enough direct sun to lower roof temps by roughly 2 degs Celsius (~3 to 4 degs F) in the peak of summer.  And there's the power generation that can be used for things like, y'know, running air con if it's required.

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #34 on: July 20, 2018, 05:47:13 AM »
Yes, I have. I've talked to my neighbor who runs the company that installed these panels about 2.5 years ago and he told us that it would be utterly pointless. He ran the numbers by putting up sensors on the roof to measure the amount of sunlight on an average day, and based on the high price of these panels (for some reason they are much more expensive here than they are in other parts of the world) they would not be producing any significant amounts of electricity to pay for themselves even after 25 years of usage.

In other words: maybe once the price for the panels goes down significantly but as it is, it's not worth it yet.

letired

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Re: My power consumption has almost tripled last month - advice please
« Reply #35 on: July 20, 2018, 10:34:18 AM »
Solar screens might be worth investigating as they sit on the outside of the window and prevent the light/heat from getting inside in the first place, whereas it's already inside with blinds and you're working to keep it contained.

South-west is the most brutal sun direction here, so you have my condolences!

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #36 on: July 24, 2018, 02:46:02 PM »
I did some more research on my insulation, talked to the neighbors, and it seems like it's not all that bad.
First: when this house was built 14 years ago, the code required an R-30 insulation in the attic. I went up there today and checked, and pretty much the entire living space is covered in around 10-12 inches of insulation foam. The temperature in the attic is very high, however my ceilings remain cool to the touch so it's not as bad as I thought it was.

However, the office remains a big problem as it gets much hotter than the rest of the house. With the thermostat set to 78F the office heats up to more than 85F in the afternoon. It's got a very high slanted ceiling with much less insulation than the rest of the house, so I will definitely need to address that. I'm just not 100% certain what the best course of action would be, but that's a topic for another thread.

AccidentalMiser

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Re: My power consumption has almost tripled last month - advice please
« Reply #37 on: July 24, 2018, 03:49:06 PM »
Many utility companies will be an energy audit on your home for a nominal fee.  You might look into that.  I think the new thermostat will help you but this whole situation puzzles me a bit.  400-500 KWH per month seems almost unimaginably low for a 1700 sq ft house.  2000 KWH in the height of summer with no shade seems reasonable to me.  As you mentioned, you can't even think about turning the unit off or you will boil in two hours.  That's a lot of heat!

Air leakage?  Are your ducts insulated or running through your 150 degree F attic without insulation?  I just skimmed the thread so I'll go back and see if you answered any of these questions.  You might also try heavy blinds/shades/curtains over the south/west windows to limit that solar gain.

« Last Edit: July 24, 2018, 03:57:30 PM by Accidental Miser »

formerlydivorcedmom

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Re: My power consumption has almost tripled last month - advice please
« Reply #38 on: July 24, 2018, 04:20:17 PM »
Solar screens are also a great idea but I already have blinds in every single window but one, and they're closed 24/7. I think the only thing I can really do is roof insulation. The way the house is built there isn't really much else I can do for extra shade.

I have blinds in every window.  We added solar screens and blackout curtains to the front of the house and it made a measurable difference in temperature in those rooms.   You might especially want those in your office area, if that is where it is getting hottest.

Our upstairs is always hotter than the downstairs; we put a big box fan at the doorway to the office and that plus ceiling fans keep us at a reasonable temperature when we are in that room.

We have spray foam insulation in the attic.  The attic never gets warmer than about 85 degrees (which is also nice for storage).  With that, and the shades/curtains and the box fan, and keeping the house on 78 during the day (74 at night because my husband insists), we used 1800 kwh last month.  (On the con side - our house is 3000 sq ft., we have a gazillion computers, and the dog door doesn't seal well.)

By October temperatures ought to be approaching "reasonable" again, and you can just be grateful you survived August/September in Austin.

Gremlin

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Re: My power consumption has almost tripled last month - advice please
« Reply #39 on: July 24, 2018, 04:42:04 PM »
Where is your study located?  Is it upstairs above your garage?

If so, have you looked at insulation on the back of your garage door?  Your garage appears to be in the south-west corner.  Our garage gets the brunt of the afternoon sun and without additional insulation it used to get oven-like. 

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #40 on: July 25, 2018, 09:21:31 AM »
We don't even have an upstairs, that's why I'm so irritated. Close to 2,000 kWh for a single-story 1,700 sqft house with a single A/C unit is too much in my book.

I've done pretty much everything I can to locate the problem but was unable to. The last three days our power consumption was at 64 kWh, 74 kWh, and 66 kWh, respectively. I understand Monday and Tuesday because it was very hot (106 and 110F) but yesterday was just 99F and the power consumption is still way too high. The A/C was also running for 15.5, 16.25, and 15.25 hours each day. Plus, the A/C was once more incapable of holding the house at 78F yesterday even though it was not that hot during the day, and in the evening when outside temperatures were down to less than 90F it still failed to cool the house to 78F and kept the A/C and furnace fan running until around 11pm.

I'll have the company that installed my A/C come over and check it out. I haven't made an appointment with them yet because I like to analyze and understand the problem first before I let anyone else look at it (I know, it's one of those stupid engineer quirks... if Aliens ever handed me a device to end world hunger I would first take it apart to see how it works).

Where is your study located?  Is it upstairs above your garage?
It's right next to the garage. I share a wall with the garage, the attic is above the garage as there is no second floor in this single-story house.

When you look at the photo the garage in indeed in the south-west corner, and it gets incredibly hot in summer, too (oven-like is exactly what it feels like). There is no insulation in the attic on the areas immediately above the garage, and the garage door gets very hot during the day (no insulation either, just a bare metal garage door. So hot it actually hurts to touch it. The study is immediately next to the garage on the right-hand side. It's got a very high cathedral ceiling that is warm to the touch in the afternoon, unlike the rest of the ceilings that remained cool to the touch.
« Last Edit: July 25, 2018, 09:27:04 AM by kms »

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #41 on: July 25, 2018, 09:29:33 AM »
Many utility companies will be an energy audit on your home for a nominal fee.  You might look into that.  I think the new thermostat will help you but this whole situation puzzles me a bit.  400-500 KWH per month seems almost unimaginably low for a 1700 sq ft house.  2000 KWH in the height of summer with no shade seems reasonable to me.  As you mentioned, you can't even think about turning the unit off or you will boil in two hours.  That's a lot of heat!

Air leakage?  Are your ducts insulated or running through your 150 degree F attic without insulation?  I just skimmed the thread so I'll go back and see if you answered any of these questions.  You might also try heavy blinds/shades/curtains over the south/west windows to limit that solar gain.
I've corrected those numbers in the meantime after finally understanding the confusing bill the utilities company sends out in case you have solar panels installed.
400-500 kWh is what I consumed in addition to what my panels produced minus the excess they fed into the grid. In other words, my total power consumption in May was closer to 1,000 kWh and shot up to 1,980 kWh in June. Thus, it didn't triple but instead double.

bacchi

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Re: My power consumption has almost tripled last month - advice please
« Reply #42 on: July 25, 2018, 09:41:17 AM »
When you look at the photo the garage in indeed in the south-west corner, and it gets incredibly hot in summer, too (oven-like is exactly what it feels like). There is no insulation in the attic on the areas immediately above the garage, and the garage door gets very hot during the day (no insulation either, just a bare metal garage door. So hot it actually hurts to touch it. The study is immediately next to the garage on the right-hand side. It's got a very high cathedral ceiling that is warm to the touch in the afternoon, unlike the rest of the ceilings that remained cool to the touch.

A recent thread by someone in Houston resulted in the OP installing rigid foam over their garage door and sealing it better.

https://forum.mrmoneymustache.com/do-it-yourself-forum!/insulating-garage-door-in-houston/

You could also add insulation on the adjoining wall in the garage.

If your AC can't keep up, it might need more freon. A 90 to 78 change should be easy for a modern unit.

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #43 on: July 25, 2018, 09:45:39 AM »
Thanks, I'll check it out. It never really occurred to me the garage door might need insulation... odd, I know.
« Last Edit: July 25, 2018, 10:00:14 AM by kms »

Gremlin

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Re: My power consumption has almost tripled last month - advice please
« Reply #44 on: July 25, 2018, 06:48:12 PM »
I'd look at both insulation on the garage door and insulation in the attic above the garage.  Sounds to me like your garage is your point of least resistance for the heat to get in, and this is particularly unpleasant if you're working in the room next to it.

+1 for insulation on the garage wall as well if above doesn't work.

lukebuz

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Re: My power consumption has almost tripled last month - advice please
« Reply #45 on: July 25, 2018, 09:23:43 PM »
I have a little HVAC background.  If your A/C is running 16 hours a day, and not keep the set temp in the house, you have an airflow problem.  My guess is your indoor furnace A-Coil is icing up (low refrigerant), blocking the air flow and heat exchange, forcing unit to run, while not cooling the house.  10 to 1 this is it.  Can you inspect your coil (pull the filter out) and peer in with a flashlight after running for several hours?  If any ice or frost, you have an problem!

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #46 on: July 30, 2018, 12:10:15 PM »
I tried to take a look at the coil but the company that replaced the AC in early June did a very thorough job leak proofing that thing.
I did also have a technician come over and inspect the refrigerant levels and they were perfect so there don't seem to be any leaks.

He did mention though that it's not unexpected for the temperature to rise by around 2-3F in the late afternoon given the location of my house and the shade situation, or rather the lack thereof. The entire South-Western side of the house in full sun with no shade whatsoever between around 10am (roof) / 11am (side walls) and shortly before sundown at 8:30pm. I borrowed an infrared thermometer from a friend yesterday and on this particular side of the house the walls were around 85F with the blinds showing a toasty 92-94F in the early evening (around 7pm). The cold air coming out of my vents in the ceiling was at between 60-66F depending on the vent whereas the return was at 79F on one and 81F on the second return duct. Outside temperatures were hovering around 100F and the inside was at 78F according to the thermostat.

The next thing I will now attempt is to get/make solar screens for the seven windows facing South-West.

One question though: there's ice-cold air coming out of that white pipe in the foreground right in front of the furnace. There's a second pipe linked with that first one that has been taped shut. Is this pipe supposed to be open or should I grab some tape and tape it shut as well?
« Last Edit: July 30, 2018, 12:13:09 PM by kms »

the_fixer

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Re: My power consumption has almost tripled last month - advice please
« Reply #47 on: July 30, 2018, 01:12:36 PM »
Try leaving your garage door open about a ft and see if that makes a difference

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zolotiyeruki

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Re: My power consumption has almost tripled last month - advice please
« Reply #48 on: July 30, 2018, 03:09:03 PM »
That looks like a drain for the condensation from the A/C evaporator coil.  If so, it shouldn't be taped shut.

kms

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Re: My power consumption has almost tripled last month - advice please
« Reply #49 on: August 03, 2018, 12:48:09 PM »
There are more news, and it looks like everything is okay in regard to our June 2018 power consumption. I may have been going crazy over absolutely nothing...

As I've already mentioned we have a smart meter, which means it's connected to the internet and reports its current data to our energy provider. I've always suspected there must be some way to access that data, and finally found on a subpage of a subpage of a subpage on the City of Austin website. It's called "Austin Energy App" and is basically a separate website where you have to register with your CoA credentials in order to access your smart meter data back to the day it was first installed. Ours was installed on 9/3/2016 so I get almost two full years of power consumption and solar production data for this house including a temperature overlay to correlate power consumption to weather.

I've spent hours analyzing the data, and am now no longer surprised about the spike in June 2018. Long story short: our power consumption was indeed within the expected range in June but significantly too low in May, which caused me to think my power consumption had doubled/tripled. Basically, there are five reasons for the spike:
  • May was comparatively cold this year.
  • June was comparatively hot this year.
  • One of my servers that I need for work was not running between mid May and early June to to a power supply failure, which saved me around 200 kWh. I completely forgot about that until a few days ago...
  • My wife and I were on vacation in May, which I found reflected in our power consumption data (which surprised me, because I did not expect it to be that obvious)
  • The old thermostat was fairly inaccurate and around 2-3F off. When set to 78, it cooled the house down to 75-76F instead. We've had it set to 80 in May but 78 in June, which means we lowered the temperature inside the house further than intended.
Unfortunately I don't have the data for summer 2016, but comparing it to last year's consumption we are actually more efficient. The house was deserted from Mid June to Mid August when we moved in, and power consumption was very low in these months in comparison. Still, 2017 summer consumption was 750 kWh in June and 800 kWh in August (which includes the final days of August where temperatures dropped to the low to mid 80s because of Hurricane Harvey). All of this combined plus the fact that the house was deserted between Mid June and Mid August makes our 1,047 kWh look ridiculously low in comparison. And regarding the new A/C: the 9 days between us returning from vacation and the day when the A/C was replaced saw an average power consumption of slightly over 40 kWh after solar, with a maximum of 52 kWh. The 9 days immediately following the replacement saw an average of 32 kWh after solar, with a maximum of 39 kWh.

In other words: it's all good, I was worried about nothing. My July power consumption was more than 15% lower than my June power consumption despite even higher temperatures: 1,009 kWh between 6/1 and 6/30 vs. 865 kWh between 7/1 and 7/31 (after solar, which adds another ~860 kWh). The reason why our power consumption is so high is as stated before that there is no shade whatsoever and that we're getting full sun all day long. I am thus going to further improve upon insulation by getting solar screens for the South/West facing windows. I will also still have to do something about my office that heats up to uncomfortable levels in summer and improve roof and wall insulation. But at least now I know that everything is okay and our consumption did not double/triple for no reason.

Thanks everybody for participating and helping. I've learned a lot this last month.
« Last Edit: August 03, 2018, 12:53:08 PM by kms »