Jeff Wisnia wrote:
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?

Yes.


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.

--
Joseph Meehan

26 + 6 = 1 It's Irish Math