# Natural Gas Cost For Furnace 1 Hour Run Time



## hammerlane (Oct 6, 2011)

I was bored last winter so decided to see how much it cost for natural gas for each hour my furnace was on. The heating season this year is upon us so thought I'd post this.

I was trying to gauge the cost(for natural gas) when my furnace has run(consumed gas) for an hour's time. I did it two ways. 
First I just took the BTU input rating of the furnace and did the calculations from there. Then someone pointed out that the BTU input rating may not be an actual value.

So secondly I needed to determine the amount of gas my furnace is actually consuming per hour.

Here are the particlars: 
1. I have Goodman model GMPN100-4 furnace. (natural gas, single stage, pilotless and an input rating of 100,000 BTU per Hour)

FIRST WAY USING BTU INPUT RATING:

1.One cubic foot of natural gas has about 1,030 BTU.

2.Divide the furnace input rating(in my case 100,000) by 1030 to get the number of cubic feet of gas the furnace will use in one hour. So 100,000(BTU) divided by 1030(BTU per Cubic Foot) is about 97 Cub Feet.

3.My supplier's bill is based on units of one hundred cubic feet(CCF) so I divide 97 cubic feet by 100 to determine how many CCF the furnace will burn per hour. This turns out to be 0.97 CCF

4.My supplier charges $.745 per CCF so it costs me 0.97 times $.745 = $.72 per hour for natural gas for my furnace to run.



SECOND WAY BY DETERMINING ACTUAL GAS CONSUMPTION:

As stated above someone pointed out that the BTU input rating may not be an actual value. So I wanted to determine how much gas the furnace was consuming per hour.

My gas meter has a 2 cubic foot dial. I set a video cam in front of the gas meter in the morning knowing the furnace would be on for at least 20 minutes to bring the house up to temperature from the night's setback. The furnace did run for about 20 minutes but I stopped my readings at 10 minutes. Here are some findings: 
In 5 minutes the furnace consumed 7.6 cubic feet of gas. 
In 10 minutes the furnace consumed 15.2 cubic feet of gas.

So 15.2 cubic feet of gas in 10 minutes extrapolated out to 60 minutes would be 91.2 cubic feet gas per hour or 0.912 CCF/hr.

At $.745 per CCF the cost is about $.68 per hour. 
From the input rating data (100,000 BTU/hr) I calcualted .97 CCF/hr. So the actual gas consumption was a little bit less that the input rating.


NOTES:

1. No other gas consuming appliances(oven, stovetop or hot water heater) were firing at the time of testing.

2. I understand that outside temp, thermostat setting and how well my home is insulated are factors as to HOW OFTEN the furnace will run. That wasn't my concern. I only wanted to know how much gas was consumed when the furnace ran for an hour. How that hour was achieved was not important. It could of been 60 continuous minutes or six 10-minutes cycles. In my case I took a 10 minute run cycle and multiplied that amount of gas usage by 6.

I have since hooked up the following 24V hour meter to the gas valve:

http://www.grainger.com/Grainger/RED...PV9?Pid=search

The meter progresses in tenths of an hour increments anytime the gas valve is open. I can tell how long the furnace runs each day, month or season. This helps with filter changes also. I've found that about every 125 hours the filter is dirty enough to be replaced.


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## kb3ca (Aug 22, 2008)

Clocking the meter is the only thing you had to do to determine how much it costs.


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## hammerlane (Oct 6, 2011)

I agree.


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## log_doc_rob (Sep 5, 2009)

To get the TRUE cost to run your furnace you need to take your whole bill, including taxes and fees and divide it by the amount of gas used, not just what the gas company charges per ccf.


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## JackDidley (Aug 8, 2011)

I'm not doing any complicated math but this winter, I will use my heat pump instead of gas, then compare the electric bills with the electric + gas bills froom last winter. Unless there is a drastic weather change, it should give me an idea of the cost/efficiency of the two systems. I may do a thread if I think I have valid results.


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## hammerlane (Oct 6, 2011)

log_doc_rob said:


> To get the TRUE cost to run your furnace you need to take your whole bill, including taxes and fees and divide it by the amount of gas used, not just what the gas company charges per ccf.


Unless you have the gas supplying the furnace metered separately then you are incorrect. What if you have a gas oven, gas dryer and gas radiant heat in garage. How will you know how much gas only the furnace used?


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## log_doc_rob (Sep 5, 2009)

hammerlane said:


> Unless you have the gas supplying the furnace metered separately then you are incorrect. What if you have a gas oven, gas dryer and gas radiant heat in garage. How will you know how much gas only the furnace used?


 That calculation only gives you the TRUE cost per ccf that you can in turn use to calculate the operating cost of your furnace. What the gas company charges per ccf on the bill does not include taxes and, fees and other BS add ons used to pad their bottom line. 

Do you have other gas appliances?

My GAS charge was $7.60 for 12 CCF
DELIVERY $14.94
CITY TAX $1.88
STATE TAX $ .23

TOTAL BILL $24.65

Gas charge was $0.63 per CCF
True cost per CCF was $2.05

Two VERY different numbers !!!


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## hammerlane (Oct 6, 2011)

Rob is that delivery charge on your bill about the same each month? I have an $18 customer service charge each month that I pay whether I use 5 CCFs of gas or 160 CCFs.

When I said above that the cost of gas per CCF was $.745 that included taxes and riders so the $.745 was actual cost per CCF


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## jagans (Oct 21, 2012)

My wife tells me that I worry too much about things over which I have no control. Im glad Im not the only one who does that. :laughing:


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## how (Feb 26, 2011)

How often does your furnace run non stop?
Turn off all other gas appliances, turn thermostat way up, clock meter for the hour, add an hour of the monthly meter rental for the hourly cost, maybe add an appropriate portion of the annual servicing fee, take off tin foil hat, look for a new hobby.


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## hammerlane (Oct 6, 2011)

how said:


> How often does your furnace run non stop?
> Turn off all other gas appliances, turn thermostat way up, clock meter for the hour, add an hour of the monthly meter rental for the hourly cost, maybe add an appropriate portion of the annual servicing fee, take off tin foil hat, look for a new hobby.


 
The answer to your question *How often does your furnace run non stop?* would be: UNTIL THE THERMOSTAT SETTING IS SATISFIED.

I didn't care how often the furnace ran non-stop. Tin foil hat still on. Doctor's orders.


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## hammerlane (Oct 6, 2011)

jagans said:


> My wife tells me that I worry too much about things over which I have no control. Im glad Im not the only one who does that. :laughing:


You could turn the furnace off and see how much control the freezing wife believes you have now.


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## mikevegas (Nov 11, 2013)

*I need help FAST. GAS CHARGE*

I am trying to figure out how much my per day charge is for natural gas?

I use @ 940 cubic feet of gas p/day in a small restaurant. I get charged .55 p/ therm. How do I calculate this?

My restaurant opened early in the year and my meter is reading 2921 X100. What do i owe on this with my price p/ therm being .55 cents?

So NERVOUS about my bill......................

ANYBODY PLEASE?!?!


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## Bob Sanders (Nov 10, 2013)

mikevegas said:


> I use @ 940 cubic feet of gas p/day in a small restaurant. I get charged .55 p/ therm. How do I calculate this?


 Interesting. Never seen a charge like this but if we do the math....

There's about 1020 BTU in a cubic foot of gas, or 0.010193175 therms (rounded off would be .0102)

$0.55 x 940 x .0102 = $5.27


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## mikevegas (Nov 11, 2013)

Bob Sanders said:


> Interesting. Never seen a charge like this but if we do the math....
> 
> There's about 1020 BTU in a cubic foot of gas, or 0.010193175 therms (rounded off would be .0102)
> 
> $0.55 x 940 x .0102 = $5.27


 
See, thats what I thought. But, that cannot be right. Its a commercial brick pizza oven that stays on all day long for 11 hours a day. That is impossible.....isnt it?


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## Bob Sanders (Nov 10, 2013)

I have no idea at all how much it costs to run a pizza oven, but I would imagine that once it's hot it doesn't take a lot to keep it that way.


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## collegetry (Feb 7, 2012)

The other day while the furnace was running I was thinking the same thing about how much its costing me in gas usage. Funny that its all worked out here.


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## user_12345a (Nov 23, 2014)

In a dual fuel application it's common practice to determine cost per BTU delivered at various temperatures and switch to gas at the economic balance point -> when both cost the same per BTU.

A lot of the time,


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## user_12345a (Nov 23, 2014)

A lot of the time, the heatpump looses ground before the economic balance point - you switch over at whichever balance point comes first.


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## ben's plumbing (Oct 6, 2011)

mikevegas said:


> I am trying to figure out how much my per day charge is for natural gas?
> 
> I use @ 940 cubic feet of gas p/day in a small restaurant. I get charged .55 p/ therm. How do I calculate this?
> 
> ...


 its been awhile....but if memory serves me..1,000 btus =1 cubic foot...100,000 btus= 1-therm.you have 940 cubic feet x 1000=940,000 cubic feet divided 100,000=94 therms x.55 =51.70 per day...


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## ben's plumbing (Oct 6, 2011)

ok so its an old post ...big deal maybe he will come back and tell us if we were right...:laughing::laughing::laughing: i bored:laughing::laughing:


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## beenthere (Oct 11, 2008)

ben's plumbing said:


> its been awhile....but if memory serves me..1,000 btus =1 cubic foot...100,000 btus= 1-therm.you have 940 cubic feet x 1000=940,000 cubic feet divided 100,000=94 therms x.55 =51.70 per day...


You reversed the math.

He used 940 CF. At 1,000 BTUs per CF, it takes 100 CF to make a therm. You divide 940 by 100. He used 9.4 therms. 9.4 times .55 equals $5.17


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## ben's plumbing (Oct 6, 2011)

beenthere said:


> You reversed the math.
> 
> He used 940 CF. At 1,000 BTUs per CF, it takes 100 CF to make a therm. You divide 940 by 100. He used 9.4 therms. 9.4 times .55 equals $5.17


 hey bt ..Iam almost sure 1- therm = 100,000 btu yes no:laughing: maybe its me but that would seem quite cheap... would you not take 940x 1000=940,000 divided by 100=94 therms x.55 =51.70


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## hammerlane (Oct 6, 2011)

Heres what we know:

1. He uses 940 ft3 per day
2. There are 1,025 BTU per 1 ft3 of gas
3. 1 Therm is 100,000 BTU
4. His cost is $.55 per Therm

Setting this up and cancelling out units see below:


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## hammerlane (Oct 6, 2011)

ben's plumbing said:


> hey bt ..Iam almost sure 1- therm = 100,000 btu yes no:laughing: maybe its me but that would seem quite cheap... would you not take 940x 1000=940,000 divided by 100=94 therms x.55 =51.70



You went wrong by dividing by the 940,000 by 100. You have to divide the 940,000 by 100,000 since 1 Therm is equal to 100,000 BTU


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## ben's plumbing (Oct 6, 2011)

thanks guys /


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