Thermostat up or down? (how much, house, calculation)

[flowbe202]

Does turning the thermostat way down save money/energy?

Talking about how "bad' the weather is going to be this year with a buddy and said I was glad I had my programmable thermostat to take care of putting the heat up or down.

Friend came back with (the shocking!) reply that I'm not saving money by turning my thermostat down and I actually waste money/oil by making it work harder to reheat the space to the new temperature.

If I'm gone for the weekend or week, I turn the heat down to 52. (No plants or furry ones.)

During the week, I drop it down to 58 when away and up to 64 when I'm home.

Buddy says I'm using more energy to heat house back up to 64 versus keeping it constant.

I say my oil bill disputes that lame theory. Plus, with my 100+yo poorly insulated abode, I'm more likely to be heating the outside than the inside and pushing global warming along even faster.

Anyway of doing some real calculations to test this theory?

[wolfgang239]

Do you have zones? Setback in unoccupied zones will yield the most benefit. Heating units run at peak efficiency when running at full bore, so I set my thermostat to 55 when I'm away and have it heat up an hour before I arrive home. When I switched from the old dial to a programmable I saved a considerable amount of money doing this rather than short cycling the system by keeping it higher all day long.

[G-fused]

I would think that the proof is in the pudding, and the pudding in this case is your heating bill.

Edit: In research, it's a simple AB design.

[NewfieMama]

I have heard this theory before and can attest to the fact that turning our thermostat down during the day decreased our oil bill. We live in an 18th century house that is not energy efficient, so like you said, maybe the constant-heat-is-better-than-fluctuating-heat theory is specific to newer homes. But we've tried both ways (not really on purpose--I had winter babies, so maternity leave = heat on all day). When not on maternity leave, we typically go through a tank of oil every 4 - 5 weeks (55 during day, 68 evenings, 60 - 68 at night depending on zone). While on maternity leave, we typically went through a tank of oil every few weeks (68 during day).

We started using our wood-burning fireplace during the weekends last year, which allowed us to turn down the heat in the main zone of our house. We saw a drop in oil use from that as well.

[flowbe202]

Originally Posted by wolfgang239

Do you have zones?

No... glorious, original radiators that I could sort of twist on/off. (But, am really just happy not touching them.)

[flowbe202]

Originally Posted by G-fused

I would think that the proof is in the pudding, and the pudding in this case is your heating bill.

Edit: In research, it's a simple AB design.

I track annual/monthly/per gal costs, but without factoring in daily temperatures (weather, heating), it is still mostly anecdotal and "feelings".

Moving to one of the smart thermometers would probably give me that data. Almost worth it.

[masshawk]

Key here is “poorly insulated,” which says you’ll save more by turning it down. And as G-fused says, your bill proves it.

Whether you save more by turning it down depends on a combination of insulation, efficiency of your furnace, and how long you’re away for. I believe most furnace models are either on or off. They don’t “work harder” to bring the house up from 58 to 64, they just have to be on longer.

I’m sure the actual math is more complicated than this, but here’s how I see it:

If your house is well insulated, say your furnace has to be on continuously for 2 hours to bring the temp up from 58 to 64, but only has to kick on for 5 minutes every hour to keep it at 64. You’d have to be gone longer than 24 hours for it to make sense to turn the thermostat down.

If your house is poorly insulated, and the same furnace has to kick on for 10 minutes every half hour to maintain a temp of 64, then your break even point would be more like 6 hours.

Then there’s the whole idea that the greater the difference between inside and outside temp, the faster the rate at which you lose heat. But combining that with different levels of insulation to translate into when to turn the thermostat down is above my pay grade

[BostonMike7]

Turning it down does save money. How much all depends on the heating system you currently have in place, and how well the house is insulated.

Long vacation for a week? Def drop it down to 50-55 degrees or so to protect the pipes. Going away for a few hours to work? Drop it 5-6 degrees. If your house is well insulated, it should take a while for the temp to drop to that low set point. A modern house may not even hit the lower limit before the heat kicks back on for your return.

Programmable thermostats are worth it, and wifi connected thermostats are even better as you can pull out your phone, pull up an App, and manually turn on, or delay, the kickin on of your heating system

[flowbe202]

Originally Posted by NewfieMama

I have heard this theory before and can attest to the fact that turning our thermostat down during the day decreased our oil bill. We live in an 18th century house that is not energy efficient, so like you said, maybe the constant-heat-is-better-than-fluctuating-heat theory is specific to newer homes.

Those homes with level floors and flat walls, too... They get all fun

[flowbe202]

Originally Posted by masshawk

I’m sure the actual math is more complicated than this, but here’s how I see it:

If your house is well insulated, say your furnace has to be on continuously for 2 hours to bring the temp up from 58 to 64, but only has to kick on for 5 minutes every hour to keep it at 64. You’d have to be gone longer than 24 hours for it to make sense to turn the thermostat down.

If your house is poorly insulated, and the same furnace has to kick on for 10 minutes every half hour to maintain a temp of 64, then your break even point would be more like 6 hours.

Then there’s the whole idea that the greater the difference between inside and outside temp, the faster the rate at which you lose heat. But combining that with different levels of insulation to translate into when to turn the thermostat down is above my pay grade

That's the ticket! Thanks. That's exactly the breakdown I was looking for. Hate arguing without facts.

I have the burner cleaned every year, so it does work as efficiently as it can, too.

When paint from previous owners count as insulation, then I'll have a well insulated home.