Anyone heat their other house/cabin in the winter?

[Walleyehooker]

I'm wondering what you set the thermostat at for minimal heat. Is it cheaper if you set it at say 45 VS 55-60 or so. 

[gunner55]

Ours gets turned down to 50 as well. We have in floor heat in the basement & garage, besides the furnace. There's a 20K propane generator that automatically kicks in if the power is out for more than 30 seconds too. We still shut the breaker off for the pump on the well when we leave this time of year

[roony]

20 hours ago, delcecchi said:

The heat loss is proportional to the difference in temperature, so if the interior temp is 70 and the outside is 0, that is a delta t of 70.   Lowering the inside temp to 69 will reduce the heat loss by 1/70 or about 1.4%.   

Lowering the temp to 60 would reduce the loss by 10/70 or 14%.   

And if it is 55 and you lower to 45, it is 10/55 less.   or 45/55 as much.   

I have not been able to find the formula to use to calculate energy savings per degree you turn your thermostat down. The reason I questioned your formula is that I remembered getting something from Xcel some time back that said you will experience 3 percent energy savings for every degree your thermostat is turned down. I looked at some sources today and almost all of them say the rule of thumb is 3 percent savings per degree. I assume these sources have a formula that must be significantly different from yours. How do you explain this difference?

[delcecchi]

2 hours ago, roony said:

I have not been able to find the formula to use to calculate energy savings per degree you turn your thermostat down. The reason I questioned your formula is that I remembered getting something from Xcel some time back that said you will experience 3 percent energy savings for every degree your thermostat is turned down. I looked at some sources today and almost all of them say the rule of thumb is 3 percent savings per degree. I assume these sources have a formula that must be significantly different from yours. How do you explain this difference?

There are two factors that would change the calculation.   

First, I assumed a temperature outside of 0 degrees since that was the question.   Even in winter, the daily average temperature is probably higher than 0 degrees.    For example, (I just looked it up) the average high in January for Sandstone, MN is 21 and the low is 1, putting the average at about 10 or maybe a little less.

Second, if the building occupied people, lights, appliances etc produce heat that isn't accounted for in "heating energy".   In this case the building is vacant, and so no lights, no showers, no cooking, no nice warm bodies.   And presumably no basement to mess up the calculation either.   

But I am suspicious of the excel number since if I turned down the thermostat 33 degrees, to 37 degrees then I should have 100% energy savings.     And we know that in January that isn't true.   

One could look at heating degree-days for the location in question for a better answer.   

[roony]

Actually there would be another factor and that would be the original set temperature. If the original set temperature is 60 degrees and you set it down to 50 degrees I would think your savings would be less than if the original set temperature is 80 degrees and you set it down to 70 degrees. This is because the further from the outdoor temperature you are the more you would save. I think most of the literature the energy companies put out is assuming you have a more common original set temp of 70 degrees and turn it down no more than 10 degrees or so. Then the 3 percent value might be viable. 

[delcecchi]

The savings in percent is greater going from 60 to 50 than from 70 to 60.   The savings in dollars is probably about the same per degree.  

The average temperature in minneapolis in January is 15.6 and the heating degree days runs around 7000.  If heating season is about 7 months or 200 days, that is 35 degrees difference inside to outside average.  So a degree is about 3%.   In January more like 2% of a bigger number. 

Did that make sense?  sort of doing this on the fly today.