How Does Lowering Thermostat Save Energy?

I just saw someone made a blog posting about how to save energy at home and I realize that there are lot of small things we can do to save the bill. Those things are normally ignored by us because they seems not a big deal, but if we calculate how much we can actually save, the number will surprise you!

heating_2713455bAbout 48% of energy use is spend on heating in a typical U.S. home in the winter. In my apartment, the winter electricity bill normally doubled, or even tripled, compared with the summer bill cost, which means the energy I used on heating almost equal the total energy amount in the summer.

We can save a considerate amount of energy by adjusting temperature wisely. Firstly, The research shows about 35% people choose to turn up the thermostat immediately once they get into a chill home. We may think is can heat the room quicker but actually it won’t. Because thermostat does not control the speed, it only control the final temperature. So when we realize the home is over-warmed, the energy has already been wasted.

Secondly, about 38% of people think it can save more energy if we turn off the thermostat when we leave the home. According to Energy Saving Trust, it actually means “these homes are heated when no-one is there to benefit and then the home is too cold when people are in the home”, because it need to warm the entire home again from the lowest temperature. Lower thermostat by 10° to 15° when you are asleep or out of the house.

Assume the indoor temperature is 70°, outdoor is 30°, house area is 300 sq.ft.

Q= U A ΔT  (U: the quantity that accounts for the insulation and how well the materials conduct or resist heat. A: the area of the surface. ΔT: the temperature difference)

Q = 300 sq.ft x (70-30)= 300 x 40 = 12,000 Btu/hr

If we make a setback of 10° for  8 hours daily, we got total heat loss

Q = 300 sq.ft x (70-10-30) = 9,000 Btu/hr

Therefore, if we simply turn 10°F down when we are asleep and out the house for 8 hours per day

(12,000 Btu/hr – 9,000 Btu/hr) x 8hr = 24,000 Btu of heat loss can be avoid.

Therefore, we can save 24,000 Btu x 30 days = 720,000 Btu of energy

Since 1 BTU/hr = 0.00029307107 kW

720,000Btu=~ 211KW

The average residential electricity rate in State College is 7¢/kWh

211KW X 7.46¢= 1,574¢ =~ $16  we can save from our monthly bill

Here is an EPA default program schedule from ENERGY STAR Program Requirements for Residential Climate Controls

Screen Shot 2015-02-08 at 9.14.12 AM

 

Since the research does not quite take the home size into consideration, no matter what the temperature you choose in your home, on thing to remember is the lower the better.

 

http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/50152/If-You-Think-Thermostat-Setbacks-Don-t-Save-Energy-You-re-Wrong

3 thoughts on “How Does Lowering Thermostat Save Energy?

  1. Ashley Lynn Davis

    I was on the same page as Richard, I never got why my parents had the temperature set at 68 and then made it lower automatically when they’d be at work and I’d be at school. But those subtle changes really do affect the bills and energy used. I didn’t know about the window thing that Karen mentioned until I came back from winter break this year to a freezing cold dorm room and my dad asked if my windows were locked. It stays a lot warmer now.

  2. Richard Jon Katzenback

    I never considered why my father was always so concerned over the temperature on the thermostat. Anytime I would change it, like from 67 to 70 degrees he would have a fit. Now that I see the calculations I realize why he cared so much about a few degrees because the amount of money he could save could be used for several other bills. So I will undoubtedly be more considerate when I next go home.

  3. Karen Kuo

    Your observations are very applicable to our daily lives!
    To be honest I never turn down the heat even when I am leaving the house, and I believe that’s probably one of the reasons my electricity bills are very expensive.
    There is one interesting fact about the heater is that if you don’t lock the window completely during the winter there are lots of heat gonna escape from our rooms. Also if you turn off the heater at several unused locations like by the entrance or living room it would save a lot of energy!

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