This week in the Dallas area a new thermostat was announced that promises to save 20 - 30% of energy costs.

I signed up, at a cost of $20 for product and installation, and a monthly cost of $9 after the first 6 months.  I can cancel at any time without penalty.

I'm curious if indeed a two-way communicating thermostat with a central service can indeed be smart enough to offer the kind of savings being advertised.  And in my case, I have an energy monitoring system where numbers can be put to the facts ( http://welserver.com/WEL0043/ ).

Here are details of the new product I signed up for:

A Texas utility, Oncor, is introducing the EcoFactor thermostat (https://ecofactor.secure.force.com/...ex?src=dfw ).  The private company behind it promises to cut 20 - 30 % off your annual power bill by tweaking the thermostat temperature throughout the day.

After you set the temperature you desire, an off-site monitoring system makes small changes to the thermostat by remote control throughout the day.

The EcoFactor thermostat makes adjustments throughout the day upon the preferences you specify.  The off-site monitoring system through the day will make 20 - 30 adjustments.  Each adjustment might save 5 cents, but after nearly 14,000 adjustments over 12 months, the savings add up.

The EcoFactor thermostat advertises that it will save the average homeowner $300 - $400 a year.

I'll periodically update here on how it goes.

Best regards,

Bill

Bill,

I have some snake oil to sell you

I suspect they might be able to support the claim in typically over designed conventional systems. Might be tougher in geo applications, but fun to watch.
Bill and Dewayne, are you able to recall your % savings in the set back experiment last year or were they ever quantified that way? That might be a yardstick that Ecofactor should see.
Joe

There are some savings to be had when the utility can control peak loads - ie, a smarter version of off-peak or interruptible service combined with setback, outdoor reset and anticipatory changes has some value. Unless you have a duplex (where you can treat the sides differently), comparison is hard - even harder to quantify is the negative effect on comfort.

Posted By joe.ami on 08 Jul 2010 12:43 AM
I suspect they might be able to support the claim in typically over designed conventional systems.
Joe

I would agree with this also. But there is no harm in trying. I would be interested in seeing documented savings after your monthly costs are included.

If I was able to save $300-$400 per year on heating and cooling cost that would cover nearly all of my HVAC cost.

I don't like the idea of 20-30 adjustments per day - it sounds like a recipe for a whole lot more compressor cycles, not a good idea. I suppose it might be possible to lengthen on and off cycles through careful adjustments, and that could be a good thing.

Bill, your logging system should quantify both savings and # of compressor starts, so do please keep us advised.

Thanks for the comments.

I see the subject as an interesting one, particularly noting that there's large dollars involved with respect to a utility (Oncor) paying a lot of money to EcoFactor if indeed they cause kWh consumption to decline.  How this is to be shown is unknown to me.

Also of particular note, while it's tempting to conclude it's a 'snake oil' subject, it's interesting to see a major utility get behind such a product.

All in all, I see it as an interesting 'science project,' that will only cost me $20 to engage.  I get 6 months to understand if indeed there's a lot of savings, and if at the end of the 6 months I'm not convinced, there's no penalty to withdraw.  The $9/mo payments don't start until a 6 month period goes by.

Who knows, maybe it's possible there's some kind of proprietary algorithm that, when taking into account outside and inside temperatures, can constantly adjust the tstat in a manner better than any conventional wisdom might recommend.

Most HVAC professionals for years have advocated, for heat pumps, that it's most cost economical to leave the tstat set at one setting.  I'd like to apply some science to see if there's a more economical way.

Yes, two years ago I demonstrated that a setback practice with GSHPs can be economical.  I didn't attempt to quantify how much, but rather to simply show yes indeed there's a cost savings.  I did it by analyzing kWh as a function of Degree-Days.  Search of the archives will show considerable material on the subject.  I used then a 4° setback, and still do.  Keep in mind a key assumption for the conclusion.  The assumption was that there is adequate loop system capacity - i.e. limitations on loop system performance don't affect the economics of a setback.

I'm ready to see if someone else's 'better mousetrap' can do better than my 4° setback routine.  Certainly it's a pretty elaborate 'mousetrap,' as it involves constantly sending data to/from my thermostat to a central analysis point.

What I'm contemplating now is how I'm going to show conclusively yes/no the product's great/stinks.

Not surprisingly, HVAC kWh trend analysis is of little use.  It's too dependent on weather and seasonal fluctuations from year to year.  I.e., see below for my monthly HVAC-only kWh consumption.

Instead, perhaps kWh consumption can be normalized to how hot / cold it is outside.  I'm going to have to think about this for a while, as I don't know how yet how to avoid the influence of kWh/DD degradation due to EWT rising.  I.e., it takes more kWh for every DD in Aug. than it does in May.

If my tstat gets changed 20 - 30 times per day, my logging system will see it.  It should be interesting to watch.

Best regards,

Bill

Looks like the old graphs are gone - do you have a long term graph of kwh/degree day for a long period? - I'm interested in seeing how noisy it is.
You should be able to correct for EWT once you have a plot of EWT vs COP.

I suspect the program is inspired by "obama bucks" that encourage utilities to inspire decreased consumption. Among the requirements are "demonstrable" reductions. Local utilites last year were offering rebates on ECM blowers (I took advantage) of $300. That rebat was discotinued as savings did not justify the program.
Keepus posted.....and don't worry about big brother telling you what temp is comfortable...lol
j

Bill, do you have time-of-use rates in your area that this thermostat may be able to take advantage of? I don't readily see how else adjustments would lower cost unless the thermostat reduces cycles-per-hour (to improve efficiency) or makes other adjustments that decrease overall system run time.

My father-in-law just signed up for this program:

"How does PECO Smart A/C Saver work?

When you enroll, we’ll install a PECO Smart A/C Saver programmable thermostat inside your facility. On selected days from June through September, we’ll automatically cycle participating air conditioners to help balance the region’s demand for electricity. These events are known as PECO Smart A/C Saver “conservation events”. The more participants there are in the program, the greater the likelihood of reduced duration for any single conservation event. PECO Smart A/C Saver works best when it is truly a community-wide effort.

What is “cycling”?

When energy demand is approaching a critical point, your device will receive a radio signal that will put your A/C compressor into a “conservation mode”. What that means is your compressor will operate half the time it did during the hour prior to the conservation event.

How will I receive my participation credit?

Bill credits of up to $30 each month will appear as a line item savings on your PECO summer bills. Because of the way the PECO billing cycles run, you can expect your bill credit in the month FOLLOWING the cooling month (June – September). For example, if you sign up before June, you will receive your first bill credit in your July bill for your June electric usage."

More info here - https://www.pecosmartacsaverprogram.com/iframe/business/faq.php

Dropping to a 50% duty cycle during a design (or hotter) day is NOT a recipe for interior comfort. If just the compressor is cycled off with the blower left running (which I bet is the case so as to minimize user perception of AC being off) comfort will get worse yet as condensate is carried off the inactive evaporator and returned to house air.

If this program takes hold, expect it to backfire in the form of contractors and homeowners specifying oversized equipment able to provide cooling during 50% duty cycling at the expense of comfort, efficiency and noise at all other times. The very last thing this industry needs is another excuse to oversize equipment, but this PECO program will encourage it.

One of the happiest days in my life occurred in mid 1995 when I left the PECO service area, I hope for good.

But PECO loves us. 

Good point.  I'll find out if the fan is set to run during the time the compressor off time.  If so, I'll ask if he has an option to run the fan only with the compressor.

He tries not to run the AC to save money and typically keeps the house warm, so this program may not be bad for him.  However, I foresee a lot of elderly people on fixed budgets jumping at this to save a little money at the expense of their health.  I wonder if they would be better off just raising their thermostat 1-2 degrees and possibly get the same savings?

Posted By engineer on 09 Jul 2010 08:56 AM

Dropping to a 50% duty cycle during a design (or hotter) day is NOT a recipe for interior comfort.

If just the compressor is cycled off with the blower left running (which I bet is the case so as to minimize user perception of AC being off) comfort will get worse yet as condensate is carried off the inactive evaporator and returned to house air.

With respect to duty cycle of the units:

In addition to anticipating more expensive TOU periods, this was my initial thinking as to how the tstat works: shut down the tstat sooner than it otherwise would, see how long it takes the structure to heat up, and then turn the tstat back on.  And do this based on some proprietary algorithm that takes into account outside temp.

I'm already at a duty cycle of approximately 3 - 4 times per hour, as illustrated by the blue line in the chart below:




With this amount of cycling I've still been able to maintain inside RH between 40 and 50% during the Summer season (see cyan and violet lines in the chart below).  I think this is primarily due to exceptional water removal capability my WaterFurnace Envision units appear to have - my guess is it's because the evaporator coils are so large.




If the EcoFactor tstat includes management of duty cycle, I'll easily be able to see if there's impact to comfort due to RH increase (if it happens).


With respect to cycling the compressor while leaving the blower fan running:

I hadn't thought of this until seeing Curt's comment here.  I'll bet this is indeed the case.  I should have thought of this too.

If indeed management of the blower separate from the compressor is part of, or key to the EcoFactor tstat strategy, then it will provide another test of a subject that I looked at quite some time ago.

My observation then was that in a non-arid climate, it's tough to accomplish cost reduction by running the blower fan only without also incurring increased discomfort due to an increased inside RH level.

Here's a chart from Trane that shows exactly what happens when the compressor is turned off while leaving the fan running:


Clearly the chart shows that the water on the evaporator coil has to go somewhere (green area).

Here's a picture of the water coming off my evaporator coil - it's a substantial amount:



I just don't live in an arid climate.

In summary, I'm guessing there's at least 3 operating principles for the EcoFactor tstat: (1) increased duty cycle of the compressor, (2) anticipation of higher cost TOU periods, and (3) blower fan management separate from the compressor.

Once the tstat is installed, we'll have some specific data to look at.

Best regards,

Bill

Posted By geome on 09 Jul 2010 12:16 AM
Bill, do you have time-of-use rates in your area that this thermostat may be able to take advantage of? ...

When you enroll, we’ll install a PECO Smart A/C Saver programmable thermostat inside your facility. On selected days from June through September, we’ll automatically cycle participating air conditioners to help balance the region’s demand for electricity. ...

No, I don't have a TOU plan.

In TX, so far, it's rare for a residential customer to have a TOU plan.  While it may be coming some day, it's not here yet.

A key advertisement for how the EcoFactor tstat saves money is anticipation of when a more expensive TOU period is coming, and taking appropriate anticipatory action.  I'm sure this works fine in those regions of the country where TOU plans are prevalent, but, it's puzzling to me to see this tstat feature advertised so prominently in my region (when we don't have TOU plans).

So whatever savings most TX consumers can obtain from the EcoFactor tstat aren't going to come from more expensive TOU period anticipation.

With the economics of the tstat, consumers will need to have at least $9 per month savings in electricity consumption just to break even, noting the tstat's $9/mo cost.  My utility rate's 12 month rolling average at the moment is right at 10¢.  So I've got to save 90 kWh each month.  With my average HVAC related kWh consumption being 580 kWh, that says I've got to have about a 16% reduction in kWh consumption just to break even.  This could be tough.

With respect to 'smart' tstat offerings like described above, in the Dallas area we have a similar offering.  The deal here is, you can purchase a 'special' tstat from the utility company that provides to you energy monitoring data and the convenience to control the tstat via the Internet.  In return for primarily these 2 benefits, you have to pay $75, and you have to accept the tstat turning off your power during high Summer demand periods for up to 15 minutes at a time (as initiated by the utility via the Internet).

Summary?  Pay $75 to give the utility an Internet connection to your tstat and to have the privilege of your AC unit being turned off during high demand periods (for up to 15 minutes).  There are no monthly credits being offered for months when the AC is turned off, or, for that matter, at any time.  Interest deal.  I don't have one of these tstats.

Best regards,

Bill

Posted By jonr on 08 Jul 2010 10:52 PM
... do you have a long term graph of kwh/degree day for a long period? - I'm interested in seeing how noisy it is.
You should be able to correct for EWT once you have a plot of EWT vs COP.

OK, here's a chart of kwh/DD for a long period (since Dec. '07) (DD is in absolute value).


Here each month's HVAC related kWh consumption is indexed by the month's Degree Days.

This chart still has some noise, especially in the 'shoulder months.'  So, taking this a step further, here's a scattergram of HVAC related kWh versus Degree Days:



Here we finally get a nice fit to the data.  The scattergram approach eliminates the low usage months (250 kWh per month and lower), allowing to see there's a nice relationship between kWh and DD once you get past about 275 kWh per month.  With the exception of one data point, a nice 'eye-ball' linear line can be drawn for all remaining points.

The line's slope is about 2.0 kWh per DD.  Thus, if the EcoStat is to provide value, then it's going to have to reduce this cost per DD.  For example, a 10% efficiency improvement produced by the tstat would translate to about a 0.2 kWh per DD reduction - i.e., about 1.8 kWh/DD.

This technique nicely takes weather / outside temperature out of the analysis.  The 0.2 kWh per DD improvement for me would translate to about 870 kWh reduction annually.  At 10¢ per kWh, the savings would be about $7/mo. - not enough to offset the monthly cost of the tstat.

Working this to solve for what kWh reduction would be needed to break even relative to the tstat's $9/mo charge, it turns out to be about 12%.  In other words, I need a 12% kWh reduction, produced by the tstat's proprietary algorithms, to break even.  12% seems like a lot to me.

In summary, for my climate, and for someone with good performing GSHP equipment, it looks like upwards of 15% or more kWh reduction is needed to make it worth the while to install something like this.

We'll see what the actual data ends up being.  For now, I think I've figured out the baseline to compare to: 2 kWh/DD.  We'll see if this comes down to 1.7 kWh/DD, long term, which would be a 15% improvement.

Best regards,

Bill

Posted By a0128958 on 09 Jul 2010 04:47 PM

Working this to solve for what kWh reduction would be needed to break even relative to the tstat's $9/mo charge, it turns out to be about 12%.

So for someone with a conventional system with 2.5 times (for example) your heating/cooling costs, the percentage needed for their break even would be only 4.8% (12% divided by 2.5).  It will be interesting to see how all of this works out.  Thank you for doing this!

Posted By geome on 09 Jul 2010 05:18 PM

So for someone with a conventional system with 2.5 times (for example) your heating/cooling costs, the percentage needed for their break even would be only 4.8% (12% divided by 2.5).  ...

First, it depends on outside conditions.  Someone with 2.5X my HVAC costs might live where weather extremes are such that DegreeDays per month are higher than what I see here in Dallas.  Such that their kWh/DD rate is the same as mine (2.0).

Second, I assume you really mean kWh consumption when you say "costs."  Otherwise someone could have much less kWh consumption than me and still have 2.5X "costs" if their utility rate is very expensive.

Let's assume the example is for someone in the Dallas area, i.e. has the same DegreeDays as me.  And let's use your 2.5X HVAC costs - i.e. 2.5X my kWh usage.

In this case, the kWh cost for every DD goes up by 2.5X - i.e, my 2.0 times 2.5 is 5.0.  So in this example, it requires 5.0 kWh for every DD - 2.5X less efficient than me.

Thus, yes, you're correct.  Break even to offset monthly EcoFactor tstat costs is as you state, about 5%, which is the 12% divided by 2.5).  Again, this is with the assumption that kWh/DD is 5.0.

There are many factors that could cause kWh/DD consumption to be much higher than mine:
1. Current tstat setting is more aggressive than me, causing the HVAC system to run much more than mine.
2. HVAC system is much less efficient than mine - more kWh are needed to reject/absorb the same amount of heat.
3. Structure is much more 'leaky' and much less insulated than mine.
4. Structure exists in a much colder/hotter climate than me.
5. Some combination or all of the above together.

I think what I've learned here is that my 'cost' to run my system for the structure I have in a Dallas environment is about 2 kWh/DD, and that it's a pretty linear relationship up to a certain point.  Now that I know this, this gives me a good method to evaluate the performance of an EcoStat tstat, that eliminates the influence of outside temperature.

Best regards,

Bill

Thanks for the excellent analysis of the kwh/dd. The definition of dd could probably be tweaked to get a better fit.

Some day we will have metrics of overall house performance that 1) can be used and compared widely and 2) can be accurately measured quickly.

While I agree with Curt's comments about fan re vaporizing condensate and it's degative impact in some areas, there are certainly areas in TX where humidity is non-issue. So much so that evaporative (swamp) coolers are used.
J

Posted By joe.Ami on 11 Jul 2010 11:54 AM
... there are certainly areas in TX where humidity is non-issue. So much so that evaporative (swamp) coolers are used.

Agreed.  (Certainly not so in the Dallas area, and particularly not so in the Houston area.)

It will be interesting to see if the EcoFactor tstat produces 20-30% HVAC related energy cost savings only if certain conditions exist, such as TOU plans or dry, arid climates.

Best regards,

Bill