This was not due to differences in weather or prices — in fact, the weather was more extreme in the year after installation, and utility prices were much higher, yet we still paid $1k less.

This was accomplished by programming it to heat only to 62 at night (10pm to 5am), and to cool only to 78 during weekdays (9am to 4 pm).

Our experience was that, if you program it correctly, the unit will almost certainly pay for itself in a single month. And you can easily measure whether it worked for you.

This, again, is incorrect in almost every conceivable case. You will indeed save money. The fact that the furnace takes a while to get the house back to the regular temperature is irrelevant in a properly designed heating system (it shouldn’t burn more fuel/ create more heat in a given period of time than can be distributed in the same period). What I said in my above post is correct and backed up by scientific fact as opposed to inherited “common sense.”

Thunderhadt’s issue does bring up a theoretical issue, and we would have to look at the overall heating design to answer it in any specific case. the issue, again, is that the heat source (furnace) it shouldn’t burn more fuel/ create more heat in a given period of time than can be distributed to the living space in the same period of time.

there could be issues with older systems where there was no thought that maybe people would want to turn it down 15 degrees at night. A knowledgeable heating specialist could tell you about your particular system, but they would have to be someone who understands your desire and perspective to save energy and money, as opposed to the perspective that has it as its goal to just ” make the temperature comfortable all the time”. In most cases, though, i believe that furnaces will only run 10 minutes at a time, then take a break before running again, and it would be only oddball cases where you wouldn’t save money over a time period of 8 hours by dropping the temperature. It’s conceivable that by changing the furnace timing and heat pumping you could save less or more than you currently are on the reheat phase, but it’s highly highly unlikely that you’d ever be actually spending more fuel on the reheat phase than you saved on the low temperature interval at night or when you are at work.

Actually, in this case your gut was wrong. Our guts are very good at things like determining whether we are being attacked by a predator and should run, and really really bad at doing math.

The truth is described by the physics of heat, and can be summarized:

Anytime you can drop the temperature of your house (in winter) for a period of hours, you slow the rate of cooling and the decrease energy usage over that entire time period. Imagine it as if heat were pouring into your house like water from a hose. Your house constantly “leaks” the heat outside to where it is colder, but the more you raise the heat inside, the faster the leaks flow.

this is an anological way of describing what is known as Newton’s Law of Cooling, which basically says that the greater the temperature gradient (the difference between the temperature of your house and the outside temperature), the faster the rate of heat loss (the leaks). Over any period of time, if you experience a slower rate of heat loss (by having a lower house temperature) you will be saving energy, CO2 (probably the most important in the long run) and money. Just remember, when you lower the temperature inside while you are sleeping, for that entire time your house requires less energy per hour to heat as compared to the same period of time at a higher temperature.

The fact that it takes a while to make up the 9 degrees in the morning does not mean that you are wasting energy. It’s just as if you are “filling” the house with heat again after you let it down in the first place. The filling doesn’s mean that it’s costing you extra money or energy, you’re just bringing the house back to the state it was originally in. In the intervening period, though, you’ve saved $$, CO2, and fuel.

Personally, I’ve invested in a great cover for my bed and some warm slippers for the morning to cover those “colder” periods.

I don’t know what those people are referring to when they are saying “improper usage of the programmable thermostat.” Of course, if you buy something you need to understand how to use it and use (program) it properly and with an understanding of what effect you are trying to create

But , in my experience, any time you can design turning the heat down into a system that you don’t have to always think about, you are going to end up saving money compared to relying on your habits and attention to adjusting things manually “when you think of it”.

I have run the thermostat mainly at a fixed temperature (around 68 in the winter and about 76 in the summer) and am now trying the programmable features. I already have one and this is what I have noticed.

When running at a fixed temperature it comes on a few times an hour and runs for a few minutes all day (24 hours).

When running in programmable mode (I am trying this right now with the heat), I get the same behavior except at night when the setting drops to the lower temperature (about 9 degrees difference). I get a few hours where the heater does not run while the house drops to that temperature. Then when it hits it, I see the same usage. But then in the morning when the house is warming back up, it takes forever to make up that 9 degree difference.

My gut seems to tell me that the overall time the heater is running is not really any less than when I am just having it sit a fixed temperature. In fact it almost feel like it is running more.

Maybe I am one of these people who are using it wrong. But I would really like to see instructions on the right way to use it as well as numbers showing the savings.

Maybe I’ll just have to be patient and compare last years usage to this years and see if there is a difference.

it’s also worth considering the amount of mercury in a CFL. it is about 100 times less than in a simple thermometer. take care when handling them and disposing of them, but you dont need to call a hazmat team.