Joseph Meehan wrote:
wrote:

Here in Michigan, it's been bitterly cold for the last couple of days.
I have an automatic thermostat which I lower the house to 65 during
the day, and back up to 69-70 at 4:30 so it's warm by the time I get
home from work.

The problem is, it took FOREVER to get back to that temp last night.
When I first came home I thought my furnace wasn't working right (had
the ignitor replaced last week), but it was running... It just wasn't
getting warm.

I change the filter regularly, but I have a lot of windows in my
house...

So the question is, is it worth it (energy wise) to lower the temp
during the day, when it takes so long to get back up to temp? I'm
thinking I'm buring as much gas to bring it back up than I might save
during the day.


You did not tell us what kind of energy you are using. If you have a
heatpump then it depends, you may or may not save or may pay more. Heat
pumps are less efficient when it is colder.


I'm not sure I follow that one Joseph. Are you saying that because the
outside air is likely to be colder in the early evenings than it is
during the days the reduced efficiency of a heat pump at lower outside
temperatures will make each "raising" BTU cost more if you replace them
in the evening than if you put them back continuously throughout the
day? And maybe by enough more to turn the whole equation around and make
your electric bill higher if you let the house temperature drop down
during the day than if you don't?

Our home (Boston area) uses two heat pumps (two zones), and the
auxillary resistance heaters have been kicking on a lot lately. It was 4
degrees F this morning, quite a bit colder than we usually see this time
of year. Global warming? Bull****!

Jeff


Gas and electric resistance don't really differ much in efficiency. So
you will always save if you are using them and they don't have a time of day
differential as electric sometimes does.

As your home cools less heat is lost so while you home cools it saves X
amount of energy and when it reaches the lower time it continues to save say
Y amount of energy. When you get home and turn it back up it will take X
amount to re-heat it, but you will not have to pay back that Y amount.

If you reduce the temperature difference by 10% you will save 10% of the
heating expense while your home is cooler.



--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"