On Jan 24, 6:49*pm, Jim Elbrecht wrote:
On Thu, 24 Jan 2013 17:32:54 -0600, "ps56k"

wrote:
What with all the various eco topics concerning when and how to run your
heating/cooling,
I have yet to see a home electronic thermostat with the added feature of -
- an elapsed run timer -

My relatively plain jane, 5 yr old Hunter does that. * I thank I paid
$50 for it- it has a couple programmable features and flashes me when
the elapsed time reaches a preset. [I use 75 hours] * Then I know it
is time to change the air filter.

Yes, I was thinking that too. Some of them have an elapsed
time counter for changing the filter.







ie - how long has the system run since timer reset ?

This would be great to see if setting the temp higher in summer,
or a little lower in winter actually changes anything
while being able to record the amount of time the furnace or A/C runs...

I take it on faith that it saves a little. *The math involved in
figuring all the heating/cooling degree days, traffic in and out,
relative humidity, wind direction, etc would make my head explode.

If the heater/cooler runs less it will save money.

Jim

And agree that the timer would not tell you much because
there are the other factors, like weather, so it would be hard
to compare and draw meaningful conclusions. Similar
info is already available on the gas or oil bill. Mine also
shows the degree days for this year and last with usage.
Another problem with the simple timer would be if you had
a two stage furnace you would not know which rate it was
firing on.

The way I look at it, heat loss is going to be roughly
proportional to temperature difference. So, if it's 20
outside and you have it at 70F vs 60F inside, the difference
is either 50 or 40. Since 40 is 20% less than 50, you'd be saving
maybe 20% on energy. However if you set it back at say
midnight for 7 hours, it won't get down to 60F for
many hours. So, you're probably going from 70F to more
like 65F average, which would be more like a saving of
10%. And then you're saving 10% for just 7 hours, which
reduces it to maybe 3% overall savings for the day. The
amount may be in question, but there isn't any doubt that
it does save some energy.