Leave heating on or turn it off?

Plumbob

You were told wrong. It is OK to turn it off when not needed.

Lynn Hudson

more efficient to leave heating on?

We have old water filled radiators run by heating oil. I have heard that it is more energy efficient to leave the system on and not allow the water to get cold than turning it off. That is, that it costs more to reheat cold water than it does to keep it hot all the time. Is this correct? Is it alright to have the system turned off during the night and for most of the day?

Firedragon_4

The trick is for every degree

of setback take no more than one hour of recovery above 32F outside. Below 32F outside, 1/2 degree for every hour of setback.

Buy a clock thermostat, I have 4, wouldn't live in a house without them, warm when you're there, saving fuel when you're not, FACT!

Mark W

Okay to have it off

but depending on the size, age & insulation in your house, the recovery time to get to the house back to an acceptable temperature might be a miserable wait.

I used to set back 10*, but by the time the house recovered, I was heading to bed. Now I just set back 5*. It's an old house, and I need more insulation & tightening up, I know!

Off is off. If you're not running the boiler, you're saving fuel.

Let's take two different scenarios:

In scenario #1, you leave the t'stat set at 70* for a particular 8 hour period during the day when you're not there. Say on a cold day it runs 15 min/hr to maintain 70*. That's 2 hours of run time.

You get home to a house that is 70*, and it continues to run 15 min/hr to maintain 70*. We'll stop counting time on our hypothetical situation at 12 hours.

In scenario #2, you set back the t'stat to 60* for the 8 hours you were gone. Boiler doesn't run at all in this time.

You get home, set the t'stat up to 70*, and it runs continuously for 2 hours to bring the house up to 70*. For the next two hours it runs 15 min/hr to maintain 70*.

As mentioned previously, in both scenarios we are contemplating a 12 hour period of time.

Scenario #1: The boiler has run 3 hours.

Scenario #2: The boiler has run 2.5 hours.

End result for both scenarios? You're in a 70* house.

Under scenario #2, if your boiler is using a 1 gph nozzle (~140,000 btu input), you have burned 1/2 gallon less oil. May not seem like much, but multiplied by the days in a typical heating season, it adds up over time. If the same setback is done twice a day, now you're saving 1 gallon of oil per day.

Yes, in scenario #2 you are waiting 2 hours for the house to recover to 70*. If you don't already have one, I strongly recommend a programmable digital t'stat that will automatically have the heat come on, and start to put heat back into the house before you get home or before you get out of bed. Not only will it turn automatically turn up the heat, but it will turn itself down as well. You'll you save fuel, and the house will be comfortable when you want it to be. No more waiting around for the heat to come up, or remembering to turn it down before you head to work or bed.

These are not exact numbers, they will constantly vary, every system is different, numbers will constantly change based on OD temperature, every house is different, people have different degrees of comfort, what they consider acceptable recovery times, etc., etc. But as far as I'm concerned, off is off, and if you're not running the boiler, you're not spending money on fuel.