Does turning down the thermostat at night save energy? Just like legal opinions or tax preparation results, ask ten professionals and you will probably get ten varying results. Well, the consensus surrounding digital programmable thermostats and their ability to save energy is about the same, ask ten HVAC experts and to some degree you will get 10 different answers.
Google this question and you will quickly see that there is a scientific approach that is very complex and requires a deep knowledge of thermal dynamics and as usual will leave the layman scratching his or her head as to what they just read. Read the next opinion written by a retired accountant and surely you will save money by setting the thermostat back by x degree, however what is forgotten here is that it takes a lot of energy to bring the temperature back to a comfortable level once you climb out from underneath those toasty blankets.
The answer lies somewhere between the two opinions as described above and a little common sense will go a long way in understanding what the facts really are, at one point the U.S. Department of Energy was urging Americans to install programmable thermostats, thought to save up to 30% and close to half of all U.S. homes have them. In 2006 the DOE stopped pushing the thermostats after numerous studies showed the actual savings was zero not because the stats didn`t work but because the home owners could not figure out how to use them correctly.
The most consistent information I could find about the real savings of a setback thermostat providing you heat with gas or oil was that you could save up to 5% on your energy usage. If you heat with an electric heat pump you probably will not see much of a savings because of the amount of run time it takes to bring the house back to comfortable level.