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The unnaturally high cost of gas

October 11, 2010
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During the winter of 2004-2005, we paid a gas bill one month of $2,520. So in the summer of 2005, when the cost of natural gas was predicted to double over the winter of 2005-2006, I knew we had to do something.

This article is about how we cut our gas consumption 26 percent (10,216 therms to 7,576 therms) from October to March. These months are generally our coldest months, when we have the floor heat on.

I don’t really mind paying to heat the water for washing — at least I know I’m getting a return on it. However, the floor heat seems like such a waste. It isn’t really, but my brain is wired for return on investment.

First a little background. We have six bays built in 1980 with new (2002) Dilling-Harris equipment. In a second building, and at a 90 degree angle, are another six bays built in 2001.

The two buildings are about 100 feet apart and run independent of each other. They share the security alarm and closed circuit TV system.

The comparisons
It is difficult to compare one year to another without considering variables, such as wind, moisture and temperature.

The wind certainly affects the heating of the bays, even though 10 of ours have no back door. To eliminate the wind tunnel effect, we keep the one door closed and pull in and back out to wash. I don’t have any records of wind average, so for this article, assume the wind blows the same from year to year.

The moisture in snow, hail or rain should stay out of the bays except for the truck bay (which is open) or when the wind is blowing. So assume that the moisture from the weather has no affect.

The water usage from washing normally would be about the same from year to year, but we had road construction during all of 2005 and sales were down, so there might be some difference.

Does the wash water, being at 110 degrees during the soap cycle and about 40 degrees during rinse, help heat the floor? If so, then with the sales being down in 2005, we really came out better than the figures show.

The temperatures for which we have records didn’t change too much from year to year, with the exception of October, which was warmer in 2005.

The average for the six months in 2005-2006 is 33.7 degrees and in 2004-2005 it was 31.5 degrees. The warmer trend in 2005-2006 may account for some of the 26 percent reduction.

To see actual temperatures, refer to Table 1.

The strategy

  1. Train all the attendants on how the floor heating system works. They are the key ingredient in the mix since they will monitor and make adjustments on a daily basis. It is important for them to understand the system.
  2. Set guidelines for when the floor heat should be on and, more importantly, when it should be off.
  3. Experiment with closing some of the 12 bays during the extremely cold temperatures to see if it will help.
  4. Design a checklist to monitor the system daily (even hourly) and keep track of efforts, results and adjustments.

I drew a sketch of the floor heat system showing the boiler, pump, thermostat and a typical bay loop with the direction of antifreeze flow.

I then wrote a narrative explaining the floor heat system in detail:

  1. How the pump circulates the antifreeze through the piping system.
  2. How and, more importantly, when to change the set point on the thermostat.
  3. How to determine the temperature of the antifreeze in the system.
  4. The default settings for the thermostats.

The intent is to keep the boiler off as much as possible, or at the lowest temperature possible, while keeping the bay floors ice free. I also included directions on when to close bays, at what temperature to close them and which bays to close.

I designed a form to be filled out by the attendants which included instructions on when and how to fill out the list and asked for the following information:

  1. Default settings for daytime;
  2. Four different ranges for the forecasted overnight temperatures;
  3. High and low temperatures, forecasted and actual;
  4. Each bay floor’s actual temperature and if the bay had ice or was wet; and
  5. A place for the attendant to write down the time and set point of any changes to the thermostat.

From October 2004 to March 2005 we consumed 10,216 therms for a total cost of $6,991. The cost per therm was 68 cents.

In the same six months of 2005-2006, we consumed 7,576 therms for a total of $8,497. The cost per therm had risen 44 cents to $1.12.

That cost was $1,508 more than in 2004-2005, even though we used 2,640 less therms. If we had not cut consumption this past winter, our heating bill would have cost us $2,991 more.

It was worth the effort and we didn’t have a $2,520 monthly bill all winter. Our highest bill was $2,165, despite the 65 percent increase per therm.


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