“Is it Cheaper to Turn the Heat Down at Home Before I Go to Work?”

February 04, 2016

Here’s a question we see often:

“I work during the day and don’t see a need to heat an empty home. Should I turn the heat down before work? Is that cheaper or does it cost me more later since my system has to run longer?”
 
It’s a great question, especially for Kansas homeowners who pay a ton for heating during winter.
 
The answer: Most likely, yes. Turning the thermostat down (called a thermostat setback) before work will save you money. But only if you have a furnace. Things get complicated when you have a heat pump
 
First, we’ll discuss why thermostat setbacks work well for furnaces and then discuss why it can be a waste with heat pumps.

Why thermostat setbacks save money with furnaces

Let’s get into some basic physics. 

Thermostat setbacks save money because of the principle of heat transfer. That is, the rate of heat loss (or gain) depends on the temperature difference between two objects.
 
Applying this to your case, we’re saying that your home loses LESS heat when your home’s temperature gets closer to the outdoor air temperature. So the lower your thermostat setback, the colder your home gets and the less your furnace runs. Meaning you save money.
 
For example, let’s say it’s 30 degrees F outside and you normally keep your thermostat set at 72 degrees F. Now, let’s assume you turn your thermostat down 8 degrees (to 64 degrees F) and then go to work. 
 
Here’s what happens:

  1. Your home starts to lose heat
  2. As your home’s temperature gets closer the outdoor temperature (30 degrees F) your home losses heat at a slower rate.
  3. Once your home gets below 64 degrees F, your furnace kicks on and runs till it gets your home to 64. Because your home is at 64, it’ll continue to lose heat at a slower rate than if it were at 72, meaning the furnace runs less often. And you save you money. Neat, right?

“But,” you object, “won’t my furnace have to run harder to get my home back to a comfortable temperature when I get home?”
 
Harder? No. Longer? Yes.
 
Most furnaces aren’t like water valves that you can “make it work harder” by turning up the thermostat to a higher temperature. You furnace works at a steady pace regardless of what temperature you set it on.
 
Also, the furnace’s running time to get your home back to normal (called the ‘recovery time’) won’t cost you more than you saved throughout the day, as you’ll see in the next section. 

How low is too low for a thermostat setback in winter?

Energy.gov provides some simple setback guidelines:

On a daily basis: Using a setback of 7-10 degrees F for eight hours a day can save as much as 10% on annual heating energy use.
 
When leaving on vacation—usually more than three days: Set your thermostat to 50-55 degrees F in the winter to prevent against freezing pipes
 
Of course, no one wants to come home to a cold home. That’s why you should invest in a programmable thermostat, which can lower the temperature for you when you leave for work, and then can get the temperature back to normal before you get home.
 
If you live in Kansas and need a programmable thermostat installed, contact Santa Fe online

Got a heat pump? Why thermostat setbacks can be a money waster

Normally, heat pumps are super efficient. But in the case of setbacks, that’s not the case.
 
Why? 
 
Well, unlike a furnace, a heat pump’s air can be pretty lukewarm—around 95 °F. But that can drop down to 85 °F if the weather outside is colder. That means the recovery time for a heat pump will be much longer.
 
You thermostat will sense that “delay” and will automatically turn on on the secondary (auxiliary or backup) heat to heat your home more rapidly.
 
The problem? The secondary heat is usually an electric resistance coil (like the ones in your toaster), and it’s super inefficient—meaning it’ll burn through the savings you made during the day in no time. 
 
Related articleHow Does a Heat Pump Work in Cold Weather?
 
The above problem won’t happen to you if one of these things applies to you: 

  • You have a hybrid heat system. Your heat pump may use a gas furnace for secondary heating instead of the electric resistance coil. This is called a hybrid heat system.
  • You have a heat pump programmable thermostat designed for setbacks. Newer heat pump programmable thermostats have an adaptive-recovery or "ramping" feature. Basically, a microprocessor senses the temperature difference to be overcome when bringing the temperature back up, allowing the heat pump alone to provide the temperature increase. This minimizes the use of costly secondary heat from an electric coil. 

Interested in a new programmable thermostat?

Whether it’s for a furnace or a heat pump, programmable thermostat can make thermostat setbacks simple and easy, saving you money year round.
 
Do you live in Kansas and need a programmable thermostat installed? Contact Santa Fe online. We can help you find the right programmable thermostat and then install it for you. 


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