A Case for Programmable Thermostats

Miscellaneous and Personal Stuff I Must Share
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Through some bizarre oversight, I went without a programmable thermostat for much longer than I should have. When you couple this with the fact that I’ve been advising people to purchase and install programmable thermostats for years, it makes me seem a bit like Al Gore and his energy-gobbling house.

However, last Winter, due to finely being tired of paying as much as $400 in monthly natural gas heating bills, I bought and installed a programmable thermostat. From day one I have operated it under an extreme setback mode – the house is programmed to let the temperature drop to 50 F during the day, then it recovers to 76 F by the time I’m home. It also drops temperature at night as well, and has different schedules depending upon what day of the week it is, so it can try to heat and cool in an optimum manner.

Yes, I know that people consistently ask in GQ “but doesn’t cooling the house down mean you use MORE energy?”, and even though I’ve been answering with links and calculations for years, folks either haven’t heard the news, have heard the news but reject it because it defies “common sense,” or they just take a masochistic pleasure in relying upon the advice of idiots to get through life. To explore the issue of whether or not a setback in temperature saves you money, see GQ, or the web, such as here: Pueblo.GPO.gov Main Page

I focus on heat and energy savings for two reasons – first, for those in the Northern hemisphere it is winter; second, I was unable to take advantage of the cooling setback due to problems with humidity and needing to cool servers that run 24/7 at my house (although I did do some adjustment).

The unit I bought was a Honeywell touch-screen one, seen here: http://www.amazon.com/Honeywell-YRTH8500D1008-7Day-Program-Thermostat/dp/B000LNUJ66/ref=sr_1_1?ie=UTF8&s=home-garden&qid=1197049447&sr=1-1 Installation was done with a screwdriver and drill, and took about 15 minutes. It was a trivial task as far as DIY stuff goes, but if you aren’t comfortable with that sort of thing you may want to ask for an installer to do it for you. Calls I made to local shops revealed a wide range of prices for thermostat installation – anywhere from $40 to $350 for the same job. It’s such an easy task that to me any cost over $100 is unjustifiable.

So how well did it work? Well, there are a lot of factors to consider here, such as differences in seasons, differences in occupancy and building use, differences in insulation level, etc. In this case, insulation and weatherstripping were not changed (save for a minor amount on garage doors in and unheated space), windows were not replaced or upgraded, and occupancy and use of the house was unchanged from prior years. Also, comfort level was unchanged – in all cases, the temperature was set so nobody in the house was ever cold in any room of the house, which was the pattern before the replacement. The largest difference to account for is the difference in the weather – after all, if one year is especially warm, and the other cold, then you could get very different results that would mask any change in heating efficiency.

Almost coincident with the thermostat replacement a new high-efficiency gas water heater was installed. To determine how much change in gas use was due to the water heater, I compared summer gas usage (when the only thing running was the water heater) between years. (And found out that the water heater is about 25-30% more efficient than the old one, but that’s another story).

Determining the weather effect was done by comparing the difference in degree-days of heating, which I gathered over the months from this website here: http://www.cpc.noaa.gov/products/analysis_monitoring/cdus/degree_days/ Degree days are a measure which is used to determine how much heating load you would have if you tried to heat your house to a constant temperature, and they are impacted not just by how low the temperature is, but how long it stays at the low temperatures. This Wiki page here can give you more information: Heating degree day - Wikipedia

So, you’re wondering, what was the net effect after buying the programmable thermostat?

Month 1: Heating load decreased by 21% from the previous year. Gas usage decreased by 29% from the previous year.

Month 2: Heating load increased by 205% from the previous year. Gas usage increased by 36% from the previous year.

Month 3: Heating load increased by 72.6% from the previous year. Gas usage by increased by 18% from the previous year.

Month 4: Heating load decreased by 20% from the previous year. Gas usage decreased by 61% from the previous year.

(Summer break)

Month 5: Heating load increased by 14% from the previous year. Gas usage decreased by 15% from the previous year.

The total gas savings was estimated as being 23,800 cubic feet of natural gas. With an LHV of roughly 900 Btu per cubic foot, that results in a savings since January of 21,420,000 Btu. If you want to equate that to gallons of gasoline (which is a false comparison since gasoline is not used to heat homes) at a lower heating value of 114,000 Btu/gallon, it would be a savings of 187.9 gallons of gasoline. Roughly 120 pounds of CO2 are produced from each thousand cubic feet of natural gas, so the furnace emitted about 1.43 short tons less CO2 since installation.

But what you’re most wondering about is how much money did it save me? The thermostat cost about $120 from Amazon, and had free shipping. It paid for itself in the first 3 months, and since installation has resulted in a total net savings of roughly $214. And it’s not even a year old yet. And note – I only used the setback for the winter months, not the summer. Someone who could take advantage of summer setback might save as much as twice that value, depending on the situation.

In my mind, this makes installing a thermostat a pretty obvious choice from a saving the environment standpoint, a comfort standpoint, and most importantly perhaps, a cost standpoint. Estimates seem to vary widely, but somewhere between 20-40% of homes have any sort of programmable thermostat; a survey among my co-workers reveals a number of about 50%. Now, while there could some reason why a programmable thermostat may not work out for some people, my guess is nearly all folks using heating and cooling for their dwelling would see a net benefit within a year or two at most.

So here’s a thought for this winter – if you don’t have a programmable thermostat, take a look at your heating bill and see if your climate and use patterns are such that a programmable thermostat could reduce your costs. Even if you live in a rented dwelling, and don’t want to improve a property which you don’t own, think about the possibility of saving money even if you write-off the cost of the thermostat.

If just a million more homes could suddenly start saving a ton per year each of CO2…well, sure, that pales a bit beside the annual U.S. CO2 emissions of 7,181 million tons per year equivalent (ftp://ftp.eia.doe.gov/pub/oiaf/1605/cdrom/pdf/ggrpt/057306.pdf). But if you save money and don’t give up comfort at the same time, why not?

2

I’ve been wanting to do this, but Himself (an electrician by trade) doesn’t think it’ll help that much. I may just go buy one anyway and make him install it.

3

It’s the perfect Christmas gift! Just like how clueless men used to give their wives irons, washing machines, and dental floss as gifts.

4

So didja review it on Amazon yet?

Does it know to automatically switch between heating and cooling? As in - set it up, and if the temp goes above 80 (or whatever) it kicks on the A/C but if it drops below 66 it switches to heat, without having to be manually switched from one to the other?

That’s a feature we’ve wanted for years and was always only available on very pricey thermostats. In the autumn and spring, our temperatures can swing so wildly from one day to another that we genuinely want heat one day and AC the next and heat the day after.

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The next frontier will be getting people to relinquish their old [del]indoor swimming pools for clothing[/del] top-load washing machines, and replace them with modern front-loaders.

Less water is used, and less gas is used to heat water and less gas is used to heat the dryer as the washer extracts so much more water from the clothes that the drying time is less.

All around, it just uses a lot less energy and water.

As a side bonus, clothes come out cleaner and it’s gentler on clothes since there’s not that corkscrew flailing away at things. Add in the rebates we got from the water and power utilities, and the thing paid for itself in well under a year.

And yes, we also have a programmable thermostat, and it’s programmed. I’ve run across several people that miss that point - they think replacing their old round goldtone Honeywell with a digital thermostat and parking it at 68 degrees is saving energy. :smack:

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I’m of the opinion that the money and fuel saved by programmable thermostats in not heating the house at times, exceeds the cost of heating constantly, regardless that the thing has to work a bit harder to get back up to temperature - in a house more perfectly insulated, this might not be so.

But as far as I’m concerned, the key advantage of programmable thermostats is comfort - I don’t want the house heated at all in the night, as we all sleep better in colder rooms. I want the house nice and warm when we wake up and are strolling around naked or getting dressed, I want it only moderately warm during the day at weekends, as we’re there, but fully dressed and active and I don’t want it on high at all when we’re out during the day on weekdays. I could achieve this by dicking about with a manual thermostat, but this is the 21st century. I have a robot that does it for me (it’s a tiny little white square, single-minded robot called a programmable timer thermostat).

7

Hmm. I wonder whether you could at times turn on the fan only to keep the servers cool and move the warm air to other areas of your home.

The humidity could be taken care of with a dehumidifier at these times.

8

I am a programmable thermostat lover.
I live in what is basically a 2000sq ft 200yr old wooden tent. The programmable thermostat (as well as anything else we can do to reduce our gas bill) is our friend.

I am not a morning person. I hate getting out of bed. I especially hate getting out of bed when the room is still cold. The gradual warming of the bedroom is what wakes me up in the winter and makes (morning) life bearable. I remember too many years growing up of racing down to the kitchen to turn up the heat. Then I would fight my mother for the corner of the room with the floor register where we’d stand and shiver and let the hot air blow up our bathrobes.
The programmable thermostat gets my vote for most appreciated piece of modern technology.

9

Yes, it will do that, and you can set the ranges yourself - such as “cool if it’s above 77, heat if it’s below 70”. I think by default there is a 3 F gap that is needed, so the system won’t oscillate between heating and cooling due to ordinary changes in temperature and inconsistency in temperature in the house.

10

I’m an HVAC person and sell and install thermostats—many of them. The tstat that Una Persson bought is a Honeywell VisionPro 8000. IME, it is the best [residential] thermostat on the market. It’s extremely accurate and provides very tight control.

We sell this thermostat installed for around $300, although obviously a homeowner can buy a version of this for around $125. (about what we pay, actually)

I would caution that most people will not see paybacks as quick/radical as the one he experiences. A setback thermostat has less benefit if, A) Someone is home much of the time. We have customers where someone is home 24/7. It’s hard to get savings if you need to have comfort most of the time. B) Setback stats are at their best if you have a predictable schedule. It’s hard to program a schedule when you don’t know your schedule!

For those interested in a setback stat consider,

  1. There are “7 day” programmables, “5 and 2” where Mon-Fri and Sat-Sun are treated as single blocks of time, and “5, 1 and 1” where Mon-Fri is one block of time and Sat/Sun are programmed independently.

  2. If you have a whole house humidifier attached to your furnace, Honeywell makes a “IAQ 9000” tstat which is [basically] the VisionPro 8000 with a built in humidistat. If you have a humidifier, you want this stat.

  3. Most programmables utilize 4 periods a day. These stats have a programming schedule that may be difficult for many to understand. One feature in the [technical] menu is “comfort setpoint limiting.” Do you have an elderly parent who might [routinely] run the stat to 77? You can limit how high or low the stat can be run to.

  4. The VisionPro has an outside sensor that will display the outside temp on the stat. if you use a heat pump, or a fossil fuel/heat pump I would suggest you get this feature.

  5. If you have a 2 stage heat pump, or 2 stage gas valves etc you will need a multi-stage version of this stat. (or any other stat)

There are other things to look for, so it might pay to ask someone before buying one.

11

Very good points which you add there, raindog.