I just bought a house with a “zone” thermostat–it automatically runs the furnace to reach different temperatures at differents times of day.
One of my neighbors swears by his–he claims that he’s saved hundreds of dollars on natural gas bills over the course of a winter. He lets the temperature drop from 70 degrees when he’s home to 60 degrees when he’s at work or in bed. My other neighbor says they’re a waste because having to jump from, say, 60 degrees when no one’s home to 70 degrees when they are uses about as much natural gas as just maintaining a constant 70 degrees all of the time.
All of us own newer homes with “code” insulation and windows. Who’s right?
There was a thread (probably more than one) on this a while back. The gist of it was that
Lowering the temperature in your house decreases the temperature differential between your house and the surrounding air, which in turn reduces the rate of heat loss. The lower the differential, the lower the rate of heat loss.
The amount of energy saved when the temperature in your house drops from say 70 degrees to 60 degrees when the furnace is off is exactly equal to the energy used to reheat it from 60 to 70.
Amount of insulation does not have anything to do with 1 or 2, although insulation slows heat loss.
Due to 1, 2, and 3, there is a cost savings which occurs only during the time when the internal temp of the house is at the lower point. The cost savings is the reduction in heat loss due to the house’s being at a lower temperature.
The programmable thermostat can save you money but I have a hard time believing this would save hundreds of dollars in a single winter.
I also think that if you are lowering the temperature during working hours and sleeping hours that you have very little equilibrium time and savings would be minimal. The temperature is almost always either rising or falling.
The only time this would not save you money is with a heat pump. I recently got a new Chronotherm IV programmable heat pump thermostat, and it ended up costing more because it would call on the aux heat (electric) to recover from the lower temp setting. Because the heat strips use much more energy than running the heat pump compressor, it ended up costing more than if I just leave the heat pump at a constant temp.
But for most all other heat sources, they do save energy. I seriously doubt it would be several hundred dollars saved in one winter. For gas heat, they really make sense. And, I like them because I sleep better when it is a bit cooler, and then it can warm the house up for me by the time I am awake.
OK, What you have is a set-back thermostat, not a zone t’stat.
Yea, unless you have extreme cold (Lake Michigan), or extreme heat (lake Havasu)
generally set back thermostats like yours are “da kine” or the best way to go.
I think one of the key factors on the amount of possible savings is how long the time periods are for the lower temp settings. Four hours straight is better than 1 etc.
The amount of gas to raise the house from 60 to 70 is almost independent to the amount of time the house was at 60. So whether the house was that way l, 10 or 100 hours, it takes “x” to raise the temp to 70. But the longer the time the house is at the lower temp, the less total energy consumed compared to 70, so the greater the savings.
I worked the calculations on this Board a long time ago, and again a slightly shorter time ago, to show that you do save money by dropping the temperature during the day. All that aside, the anecdotal evidence of nearly everyone who has a programmable thermostat is that they save an outrageous amount of money, and quickly pay for themselves. With spot gas prices breaking $7 per MBtu at the Henry Hub again, and predictions of more than $10 per MBtu, plus the continuing crunch of energy supplies and prices in the East and Eastern Interior of the US (see my articles on that) this Winter might be the one to drive people to switch to better thermostats.
You’ve lived in California all your life, haven’t you? Around these parts, pipes freeze if you leave the heat off too long. And even if that wasn’t an issue, coming home to a house that’s 20 degrees on the interior is a bit hard core.
Yes but not the point of that statement. The only thing I deal with in that statement is the energy saved in dropping vs. the energy used in rising. Some people mistakenly think that you save money in the falling range because your furnace it totally off during that falloff but they forget that you’ve got to warm back up again later.
Another way it saves money is by returning the temperature to the programmed value at the next scheduled change, My wife will often get cold and bump it up a few degrees. Without a programmable thermostat, it would stay at the higher temp until I noticed that it felt too warm or that the furnace had been running non-stop.
Now she can raise it a few degrees if she gets a chill and within 4 hours or so it is back to normal. Also, no more forgetting to drop it back at night or when leaving the house for the day.
My bill dropped 30% from 2002-3’s winter to 2003-4’s winter. And the gas was more expensive the second year.
Do you have thermostatic valves on your radiators ? That way you can control the temperature individually in every room . Perhaps having the bedrooms cooler than the living rooms. That could save you some money.
Go for it – there’s no question that keeping your house colder will save gas, even if you’re heating it back up again at some point. You might even be able to get one for free or cheaper if you get an energy audit from your gas company. Most of them have programs where they’ll for free send someone out to your house to look for ways to save gas, and tell you about savings programs. My neighbor got a controllable thermostat for way cheap that way (I think they even installed it, not that it’s anything more than tightening a couple screws).
What I do is program mine so that even during the hours I’m supposed to be home (evening, weekends), it’s colder than I really like. Then whenever I get cold I can just bump up the heat, and the thermostat will automatically reduce the heat back down later. That way if I’m out one evening, or doing calesthenics or whatever and don’t need the heat, I’m not paying to heat the place up fully.
In fact, I’ve considered just setting the temp for 60 degrees even for evenings, and just bump up the temp when I get home.
Of course, my place is small enough to heat up reasonably quickly.
