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Why am I using more gas overnight than during the daytime?

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  • Jan 14th, 2022 8:10 pm
[OP]
Newbie
Feb 6, 2011
13 posts
3 upvotes
Toronto

Why am I using more gas overnight than during the daytime?

Hi there! Located in Toronto and its my first winter in a drafty 95yo, 1400sqft house with a 13 yo furnace.

Normal gas bill up to November was about $30-$40/month. After that my monthly bill has increased quite a bit - you can see my gas usage has increased over 10x. I was for sure expecting a larger increase over the winter but want to make sure this big of a jump is reasonable. I have an Ecobee but my online account doesn't show me runtime data (it says not enough data?), so I've taken to manually reading my gas meter to get an idea of how much I use daily. I check it twice a day, 9am and 9pm. I notice that between 9am-9pm, I use about ~5m3 but between 9pm-9am, I use ~8m3. This varies by day but the overnight use is always higher...this doesn't make sense to me? Why would I use more gas overnight than during the day? My thermostat is set at 21.5 during the day and 19 at night. Stove is electric and no one is using the dryer or taking a shower at night so I can't think of other appliances using gas. Help please?
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15 replies
Deal Addict
Nov 6, 2014
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Because its colder at night without the sun and your furnace has to compensate for longer run times to maintain the same same temp.
[OP]
Newbie
Feb 6, 2011
13 posts
3 upvotes
Toronto
Is it that simple of an explanation? Thank you!
Deal Expert
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Feb 11, 2007
19455 posts
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GTA
fordmaple wrote: Because its colder at night without the sun and your furnace has to compensate for longer run times to maintain the same same temp.
This would be my assumption as well. Along with that, during the day your have more other devices outputting heat, like stove, computers, TVs, etc as well as heat from the sun.
Depending on when you take showers, your nights may also include a lot of water heating if your shower is just before 9pm, as the tank takes a while to catch up.
Your furnace is also working hard before 9am to get the house back up to 21.5C, and spending the evening before 9pm cooling off to 19C.
If the women don't find you handsome, they should at least find you handy.
Deal Addict
Nov 6, 2014
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lala_298 wrote: Is it that simple of an explanation? Thank you!
Recently in GTA, we've have -15 -20 temperature swings in the night time. That's significant. If you have an older house (assuming because you're in Toronto) your house is likely built without the energy savings products used in todays new home build. Things that con contribute to this is Windows, insulation and something as easy as what direction your house faces.
[OP]
Newbie
Feb 6, 2011
13 posts
3 upvotes
Toronto
engineered wrote: This would be my assumption as well. Along with that, during the day your have more other devices outputting heat, like stove, computers, TVs, etc as well as heat from the sun.
Depending on when you take showers, your nights may also include a lot of water heating if your shower is just before 9pm, as the tank takes a while to catch up.
Your furnace is also working hard before 9am to get the house back up to 21.5C, and spending the evening before 9pm cooling off to 19C.
Got it, thank you!
[OP]
Newbie
Feb 6, 2011
13 posts
3 upvotes
Toronto
fordmaple wrote: Recently in GTA, we've have -15 -20 temperature swings in the night time. That's significant. If you have an older house (assuming because you're in Toronto) your house is likely built without the energy savings products used in todays new home build. Things that con contribute to this is Windows, insulation and something as easy as what direction your house faces.
The spikes in my gas bill during Nov and Dec were back when the weather was still above 0 and mild. I am not looking forward to what it will be this billing period Neutral Face
Deal Guru
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Mar 13, 2004
13096 posts
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Ontario
You may want to look into sealing up any drafts in your home. Around windows and doors & similar areas to help keep the home warmer. You can also look into insulation such as in the attic to see if there is a reasonable amount currently. Also if you have really old windows that could be something you may want to look into changing out in the future too.
Deal Fanatic
User avatar
Oct 13, 2008
6254 posts
2890 upvotes
Durham
lala_298 wrote: Hi there! Located in Toronto and its my first winter in a drafty 95yo, 1400sqft house with a 13 yo furnace.

Normal gas bill up to November was about $30-$40/month. After that my monthly bill has increased quite a bit - you can see my gas usage has increased over 10x. I was for sure expecting a larger increase over the winter but want to make sure this big of a jump is reasonable. I have an Ecobee but my online account doesn't show me runtime data (it says not enough data?), so I've taken to manually reading my gas meter to get an idea of how much I use daily. I check it twice a day, 9am and 9pm. I notice that between 9am-9pm, I use about ~5m3 but between 9pm-9am, I use ~8m3. This varies by day but the overnight use is always higher...this doesn't make sense to me? Why would I use more gas overnight than during the day? My thermostat is set at 21.5 during the day and 19 at night. Stove is electric and no one is using the dryer or taking a shower at night so I can't think of other appliances using gas. Help please?
Oshawa ... 1800sf detached ... built in 2006 ... new Lennox furnace in Oct 2019

Enbridge gas consumption extracted off of their site to 2021-12-15:

Enbridge - consumption - 2021-12-15.jpg


Usage is normal in winter months.

I set my thermostat at 18 degrees all the time ... I work from home in the unfinished basement and have a portable heater that I turn on when needed.
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[OP]
Newbie
Feb 6, 2011
13 posts
3 upvotes
Toronto
jdmfishingonly wrote: Oshawa ... 1800sf detached ... built in 2006 ... new Lennox furnace in Oct 2019

Enbridge gas consumption extracted off of their site to 2021-12-15:

Enbridge - consumption - 2021-12-15.jpg

Usage is normal in winter months.
Yeah, our usage pattern is definitely similar. Thanks this makes me feel better! Although it looks like you are paying a higher rate for your gas.
Deal Addict
Jun 26, 2019
2003 posts
1733 upvotes
GTA
lala_298 wrote: Is it that simple of an explanation? Thank you!
In essence this is correct, the one thing that I would like to add to this is that your rate of heat transfer or heat loss to the outside in this case is proportional to the temperature difference between inside and outside.

So in addition to the other heat sources you get during the day via cooking or through radiation from the sun, the difference in temperature is further compounding your energy loss on day vs night. IE, if it is 21.5 inside and -5 outside, it takes a lot less energy compared to 19 degrees inside and -10 outside.

Also, the heat loss rate increases as the temperature delta increases. An example of this, would be that if its -10 outside, heating your house from 18 to 19 takes more energy than heating your house from 17 to 18 because your house is losing heat faster the higher temperature it is at. This is why decreasing your thermostat during the winter results in a non linear savings in energy.

As others have said the other side to this equation, is how good your insulation is and what your air leakage is like, both of those will help decrease your energy use, however, it is still directly correlated to the temperature delta and your R value. So you're still expending progressively more energy to keep your house at higher and higher temperatures as your rate of heat loss is increasing accordingly.

Hopefully that makes sense, let me know if you want some further clarification.
Deal Addict
Apr 26, 2003
2274 posts
1331 upvotes
GTA
If you have a 95 year old home, I doubt you will have insulation in the walls. My 50 year old home is double brick construction so all the exterior walls have no insulation and now that it's -10 to -20 at nights now, the exterior walls are freezing cold. I don't want to think about how much heat loss I'm suffering through the walls, but it is what it is. I do get quite a bit of afternoon sun as my house faces west, so that helps to heat up the house during sunny days, but yeah, having an older home requires that you suffer higher heating and cooling bills as compared to a newer home with better insulating materials built into the house.
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Oct 13, 2008
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Durham
lala_298 wrote: Yeah, our usage pattern is definitely similar. Thanks this makes me feel better! Although it looks like you are paying a higher rate for your gas.
HWT rental is included in the full invoice ... about $33+tax
16'x11' Living Room 11' Cathedral Ceiling. Hisense 65Q8G. Denon AVR-S740H 7.2 setup. Jamo Classic 10 280W Towers - FR+FL; Polk S35 - Center; Klipsch R51M - RR+RL; Klipsch R14M - Dolby FHR+FHL; Polk HTS10 Subwoofer x2. Unlocked Android Boxes from Taiwan x2
Sr. Member
Oct 25, 2017
981 posts
1008 upvotes
Similar usage to me with a 100yr old house in Hamilton, house is drafty af in places. This weekend will be perfect to go round and seal anything you can where you can feel cold air coming in, will be what I’m doing as didn’t do it last year which was our first winter in the house.

Also, do yourself a favour and switch to equal billing for gas and hydro, you’re going to have the same fun with your hydro bills in the summer if you got central a/c in that house.
[OP]
Newbie
Feb 6, 2011
13 posts
3 upvotes
Toronto
SubjectivelyObjective wrote: In essence this is correct, the one thing that I would like to add to this is that your rate of heat transfer or heat loss to the outside in this case is proportional to the temperature difference between inside and outside.

So in addition to the other heat sources you get during the day via cooking or through radiation from the sun, the difference in temperature is further compounding your energy loss on day vs night. IE, if it is 21.5 inside and -5 outside, it takes a lot less energy compared to 19 degrees inside and -10 outside.

Also, the heat loss rate increases as the temperature delta increases. An example of this, would be that if its -10 outside, heating your house from 18 to 19 takes more energy than heating your house from 17 to 18 because your house is losing heat faster the higher temperature it is at. This is why decreasing your thermostat during the winter results in a non linear savings in energy.

As others have said the other side to this equation, is how good your insulation is and what your air leakage is like, both of those will help decrease your energy use, however, it is still directly correlated to the temperature delta and your R value. So you're still expending progressively more energy to keep your house at higher and higher temperatures as your rate of heat loss is increasing accordingly.

Hopefully that makes sense, let me know if you want some further clarification.
This was very helpful, thank you!

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