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hammerlane 10-06-2011 01:51 PM

Natural Gas Cost For Furnace 1 Hour Run Time
 
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.

kb3ca 10-06-2011 05:45 PM

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

hammerlane 10-07-2011 06:37 AM

I agree.

log_doc_rob 10-08-2011 09:03 PM

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.

JackDidley 10-08-2011 09:17 PM

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.

hammerlane 10-09-2011 06:08 AM

Quote:

Originally Posted by log_doc_rob (Post 744773)
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?

log_doc_rob 10-09-2011 08:16 AM

Quote:

Originally Posted by hammerlane (Post 744967)
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 !!!

hammerlane 10-09-2011 01:02 PM

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

jagans 12-15-2012 04:02 PM

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:

how 12-15-2012 05:13 PM

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.

hammerlane 12-16-2012 07:17 AM

Quote:

Originally Posted by how (Post 1073642)
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.

hammerlane 12-16-2012 07:18 AM

Quote:

Originally Posted by jagans (Post 1073594)
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.

mikevegas 11-11-2013 09:55 AM

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?!?!

Bob Sanders 11-11-2013 11:19 AM

Quote:

Originally Posted by mikevegas (Post 1265274)
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

mikevegas 11-11-2013 11:26 AM

Quote:

Originally Posted by Bob Sanders (Post 1265304)
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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