Check my math please

[bigtiller]

If 68 degrees needs 1000 gallons of propane to achieve,,,, how many gallons of propane is needed to reach 70 degrees?

I came up with 1029 but it's been a long time since algebra class.

We have decided to raise the temperature in the house this year. It's only been one day since the big cold front moved down from our friends up north and we are already tired of winter!

 

[LD1]

correct as far as algebra is concerned, but there is more to it than that.

the warmer your house is, the quicker it will loose heat to the outside. (greater temp spread transfers heat quicker).

The amount of propane needed isnt going to be linear. As well as different winters. This winter may be colder, it may be warmer.

 

[uglyboywith11fingers]

you may be a bit low... general rule of thumb is 2% to 2.5% increase in energy consumption per degree F increase.
and as LD1 says, many other factors come into play... like insulation level, wind exposure, average outside temp in winter.

Pete

 

[zzvyb6]

Thermal problems are exponentials (nonlinear), so

All things being the same as last year, then since

1000 = e^(q*Temp) gives q = 6.90775528 . This is the thermal efficiency constant of your house at about 68 degrees.

so: e ^ q * New_Temp) ~ 1226 gallons. Its a little more complicated than that because of considerations for absolute zero, etc, but...

You might consider a lower night time setback temperature to help out, but it will use fuel to get back to 70.

Setting it to 72 degrees would take 1501 gallons.

 

[mjarrels]

This thread makes my head hurt!

mark

 

[bigtiller]

I used 1000 gallons as a base line because for the past 15 years it has used an average of 936 gallons, so I just rounded up a little. Plus, I heat the garage with part of that 936 and that part is infinitely variable.

So I guess I should raise my estimate to 1200 and hope I am high.

zzvyb6
I knew there were some math majors out there and you told me exactly what I wanted to know. If I would have tried a little harder in school ....... next time!

 

[CobyRupert]

We have decided to raise the temperature in the house this year. It's only been one day since the big cold front moved down from our friends up north and we are already tired of winter!

"We" decided ehh? Ok, sure, if that's the story you're sticking to. :laughing: (p.s. Your wife isn't going to be swayed to turn it back down to 68 no matter how much fancy math or thermodynamic equations you impress her with. )

 

[zzvyb6]

Just think: If you set the temp back to 66 degrees, you would only use 816 gallons.

The q factor is actually 0.10158463645 based on the usage at 68 degrees. so e^(q*temp) gives you the gallons.

In Michigan right now, propane is about $2.00 per gallon. The State is strongly suggesting to top off NOW because after January 1st, the price usually leaps as homeowners realize they are almost out. Funny how that works, eh ?

My dogs let it be known CLEARLY that it was 70+ or else your gonna need a Rug Doctor. I bit the bullet, pulled the trigger, sucked it up, etc. to run an 800' natural gas line. Paid for itself in one year (furnace and hot water were fuel oil). As I get older, 72 deg. seems more comfortable....

 

[dave1949]

The relative humidity makes a big difference in how a given temperature feels on your skin. That is something to consider if your house tends toward dry in the winter.

I have also noticed our large south windows, which are big radiant heat losers after dark, can make it feel cool when sitting near them. The only reasonable cure I know for that is thermal drapes.

 

[bigtiller]

I have to admit, this 70 degrees feels pretty nice, I think 68 is a thing of the past. We have a whole house humidifier on the return side of the furnace but I haven't turned it on yet, the sump pump is still running 3 or 4 times an hour so when it slows down some more I will turn on the humidifier.

If I knew what e^(q*temp) means, I might be tempted to play with the calculator.