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Anyone good at math? Natural Gas Usage [Archive] - DVD Talk Forum


View Full Version : Anyone good at math? Natural Gas Usage

10-29-07, 07:42 PM
I am turning to the Otter to try to answer a question.

I am in need of an average monthly cost in U.S. Dollars to heat the following:

720 sq. ft. one-level structure
Average outside temperature of 20 degrees F
Indoor temperature averaged at 50 degrees F
Natural Gas Heater operating at 70% efficiency
$9.99 per MCF

Let's assume that the windows and doors have little leakage from drafts, and that the structure is insulated.

I don't need an exact monthly dollar amount just something approximate based on the above info.

I'm horrible with math and the above are the only variables that I have.

Thanks in advance for pondering this for me.

10-29-07, 07:57 PM
Wear sweaters or coats at 50 degrees indoors.

Looks like 699.30.


10-29-07, 08:09 PM
Wear sweaters or coats at 50 degrees indoors.

Looks like 699.30.


$699.30 per year, or per month?

10-29-07, 08:23 PM
I get (based on heat loss of 3,182.93 btu/hr.)

1000 btu / cubic foot of natural gas
70% = 700 btu / cubic foot

so you need 3182.93 / 700 = 4.55 cubic feet per hour

4.55 * 24 hour * 30 days = 3276 per month.

at the rate you listed, it's 9.99 per 1000 cubic feet that would be:

3276 / 1000 * $9.99 = $32.73 / month.

That sounds quite low, to be honest, so I would expect I made a mistake somewhere. Actually, 50F indoors sounds too low. Are you sure it shouldn't have been 70F, so that your delta T is 50? if that's the case:

Use 5317 rather than 3182 above and you end up with $54.63 / month.

The heat loss calculator is here, if you want to get more accurate details by using window measurements, and many other factors that really should be considered:


I would also add that I don't know how things are in Ohio, but here we get additional charges on our gas bill, in addition to the cost of the natural gas. There is a 'delivery charge', customer charges, etc. I don't have a bill in front of me or I'd list them all.

10-29-07, 08:24 PM
Just to help OldDude with another variable, it seems as if the average heating degree days in Ohio is roughly 5800.

10-29-07, 08:34 PM
I would further add that I don't really know what I'm doing, so if Ernestrp does, then please ignore what I've written. I just tried to figure it out logically.

Mrs. Danger
10-29-07, 08:36 PM
Just ask the local gas company what sort of bill to expect.

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