There is an expensive myth out there about heating and cooling that is believed by far too many people, so today we are going to put an end to that myth once and for all. When heating your house in the winter or cooling your house in the summer the most pain free way to save is to not run your furnace/ air conditioner when you aren’t in your house, and have it return to more comfortable temperatures only when you get back home.
When discussing this with people far too many times I have heard somebody say something to the effect of “I don’t do that because you use more energy heating the place back up/ cooling the place back down than you would if you had just left it the same temperature all day” From now on, we will refer to this opinion as the myth of heat inertia, and what I want you to know about heat inertia is that heat inertia doesn’t exist.
A quick physics lesson
Inertia is the tendency of an object to resist a change to it’s state of motion. This tendency means we most put energy into an object to either speed it up or slow it down. This is why it takes less energy (gasoline) to keep a car going the same speed than it does to slow a car down, then speed it up again to it’s original speed. I refer to heat inertia as heat inertia because I think most people get confused about how heating and cooling work, because they confuse it with how motion works. This is not true. The rules of motion do not apply to the rules of thermodynamics (heating and cooling), and inertia is not a concept that can be applied to heating and cooling systems.
During the summer, it takes less energy to let your house heat up during the day when you are away, then cool it down at night when you return than it does to just keep it the same comfortable temperature all day. The reverse is also true in the winter.
A thought experiment
To prove this point, lets think about your air conditioner for a minute. Your air conditioner has two possible modes, it can either be off or it can be on. When it is on it is using electricity, and when it is off it is not.
Now imagine what happens when you leave your house the same temperature all day. Because your house is not perfectly insulated, some of the cool air in your house is sneaking outside, and some of the hot air outside is sneaking in. So every once in a while your air conditioner has to switch itself back on to cool your house down. But what happens to that air that it cools down? Well, that air also eventually sneaks back outside, so your air conditioner will have to switch itself back on after a while. Your air conditioner will have to run all day to keep things cool.
On the other hand, now imagine you let your house get hot while you are away during the day. Your air conditioner gets to take a break all day long and not use any electricity. At the end of the day, it will have to kick on a run a little longer than it normally does, but the total time it is on during the day is still much less than if it had been running all day long. Less running time means you pay for less power, so you can see now that heat inertia definitely doesn’t exist, and is a bad reason to let your house stay the same temperature all day long.
How to save on heating and cooling
So I recommend turning your house’s temperature up and down depending on if you are at home or not. Of course, it can be a little difficult to remember to do that all the time in today’s busy world, so the best way to do this is to automate the process.
To automate the process of heating and cooling your house, you are going to want a programmable thermostat, which can be purchased for as little as $20. I have used several programmable thermostats over the years and I have found that while they all do their job, the more expensive ones are easier to program and let you fine tune your schedule a little more. In addition to being cheap, programmable thermostats are also fairly easy to install. I can barely use a screwdriver, but after carefully reading the directions I have always been able to put one in without any trouble.
If you are really into saving money, then you should check out the Nest Learning Thermostat – 2nd Generation T200577. This bad boy may have a fairly high cost up front, but you will make up for that initial cost with energy savings later on. The whole thing is a little complicated, but the point is it uses artificial intelligence and sensors to figure out when you aren’t home and when you are coming back to make sure your heating and cooling system runs as efficiently as possible.
A great tool in the case of messy divorces
There is one final reason you might want to have a programmable thermostat and that is it might come in very handy in case you want petty revenge against a former spouse in case of a divorce. Don’t understand?
Photo by tuchodi. Links are affiliate links which help raise money for the charity noted in the right hand side of this page.