Can you really save $ by keeping the heat at 70 instead of 80?

Question

Ignoring how long it takes initially to heat the house to 70 or 80 degrees, maintaining the temperature once it's there should take the same amount of heating. Yes or no? IE, heating the house from 69 to 70 degrees takes the same amount of energy to go from 79 to 80?

Ok, I think those of you that say it cost less at 70 are right, but something still doesn't make sense to me. Raising the air one degree uses the same amount of energy regardless if it's from 69 to 70 or 79 to 80. So why would it be cheaper at 70?

I realize that there must be cool air coming in or the the temp would stay constant. Say the outside air is 40. Obviously raising 40 to 80 takes more energy than 40 to 70, but the heater kicks on at 69 or 79, not 40. Can someone clearly explain this part? Sources would be nice.

Answer 1

Yes, you would lose more energy trying to maintain your house temperature at 80 degrees than at 70 degrees. If you look at Newton's Law of Cooling it would tell you that the rate of heat transfer across a material, like your wall, not only depends on the thickness, area, and conductivity of the material, but also the temperature difference across the material. A higher temperature difference equals a faster rate of heat loss.

dT/dt = k (T-T0) Where T is the temperature inside your house, T0 is the temperature outside your house and k represents all the constants related to this problem (conductivity of wall, thickness of wall, etc.)

So if the temperature is 70 degrees or less, you will lose more energy with your thermostat set at 80 degrees versus 70 degrees, your furnace will need to make up for this extra energy loss and will use more fuel resulting in a higher bill for you.

Answer 2

Heat loss to the surroundings is more when the temperature is maintained at 80 degrees rather than 70 degrees for a fixed temperature of the surroundings. To compensate the loss, you will have to burn more fuel or supply more electrical energy to maintain 80 degrees rather than 70 degrees.
So the answer is Yes, you will save $ by keeping the heat at 70 instead of 80.
Heating the house from 69 to 70 degrees takes the same amount of energy to go from 79 to 80. Yes, this is correct.
But I do not see any relationship between the two statements.

Answer 3

It will not take the same amount of energy to go from 79-80 as from 69-70.

The issue is the hotter something is the faster it tries to cool off ( equalize temperature) So, going from 69 to 70 takes less enegery to get to that one higher degree , ( its burning more fuel to go from 79 - 80 because it is loseing more energy to the outside durning the transistion than going from 69-70)

rambles a bit i know but i hope you get it.

Answer 4

Think of an extreme situation - if it's 70 degrees outside, then you will need no heat to keep your house at 70 degrees inside. If you bring the temp inside up to 80 degrees and then turn off the heater, you will invariably lose some heat to the outside, so you will need to turn the heater on again as your house cools down. How often you need to turn the heater on depends on how energy efficient your house is, of course, but no house is 100% energy efficient - all houses will lose heat.

Answer 5

Even after considering the assumptions you established, one must remember that Newton's Law of Cooling (see link below) informs us "the rate of heat loss is proportional to the difference in temperatures between the body and its surroundings."

Thus, maintaining an internal temperature of 80 degrees when the exterior temperature is 60 degrees does indeed require far more heat than a setting of 70 degrees.

Hope this helps!

Answer 6

NO The formula for the energy required i H = UA delta T

Delta T refers to the difference in the indoor temperature and the outdoor tempurature. The hotter the house is the more heat flows through the walls to the outside.

Answer 7

No, because houses leak. If you stop heating them, they become the same temperature as the outside.

Answer 8

Yes.

Answer 9

my dad talked about how he saved money..and i couldnt even tell he turned down the heat

Answer 10

yes