Do Programmable Thermostats Save Energy?
I see people misrepresenting programmable thermostat concepts all the time, so let's set the record straight here and now. Yes, when you set the thermostat back so your air conditioner or heating system doesn't run as much, you can save energy. I do it all the time.
It's simple physics† . The rate of heat gain in summer and heat loss in winter depends on the temperature difference between inside and outside. When you get those two temperatures closer together, your HVAC system doesn't have to run as much.
I have a programmable thermostat. That's it in the photo above. Four years ago, before I replaced our air conditioner, we had a non-programmable thermostat. We actually saved more energy with the old one than we do now.
Wait a minute! I thought you said your programmable thermostat saved you energy?
No, that's not what I said at all.
That's right. I said I save energy by setting my thermostat back. Before I installed the new AC, those setbacks saved me more energy because the old system was 25 years old and very inefficient. The less it ran, the more we saved.
The problem here is that people confuse programmable thermostats with thermostat setbacks. Two entirely different animals!
Many people who have programmable thermostats leave them in the 'permanent hold' position, as we do because we don't have a regular enough schedule. A lot of people with either kind of thermostat use setbacks to save energy.
Thermostat setbacks are where the energy savings come from.
Programmable thermostats may or may not be programmed or manually adjusted for setbacks.
So, the answer to the title question is:
No, programmable thermostats do not save energy. Not without some help from you anyway.
† I know some of you think the term 'simple physics' is an oxymoron, but that's probably just because you didn't have a good physics teacher. Physics, though, really is simple. If the fundamental ideas weren't so simple, we never would have made so much progress. Right? Here: On which days of the week does gravity pull you downward? Which direction does heat move? See? I told you it was simple!