Factors that Affect Natural Gas Measurement & Conversion to Therms
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The meters used by the Department of Public Utilities to measure customers' gas consumption are positive displacement meters which measure gas in cubic feet. Customer bills are based on “CCF" or 100 cubic feet converted to Therms. Positive displacement meter measurements are affected by the atmospheric pressure on the meter. At high atmospheric pressure (near sea level) more gas molecules are included in a cubic foot of gas than at low atmospheric pressure (in the mountains).

Two Conversion Factors.

To enable our customers to compare gas prices from one region to another, we use a standard gas measurement unit, the Therm. Initially, a conversion factor must be used to convert CCFs to the standard atmospheric pressure, which is sea level pressure. Then another conversion factor must be used to adjust for the heat content of the natural gas which also converts the sea level CCFs to Therms. One Therm is equal to 100,000 British Thermal Units. Therms are a standard measurement and billing unit for natural gas consumption across the nation. 


1.  Elevation. The first conversion factor, which is roughly 0.8 depending on exact altitude, converts our local CCF meter read to CCF at sea level.  For White Rock this factor is 0.81, for Los Alamos townsite this factor is 0.78.

2.  Heat Content/Therms. The second conversion factor, which, in our example, is approximately 1.054, adjusts for the heat content of the natural gas which varies by calendar month. The resulting output is in Therms.

About Variable Heat Content.

Gas gathered from many different wells reflects many different levels of heat content. We monitor these levels, receiving monthly weighted averages of heat content from our gas supplier. We change our Variable Heat Content Factor monthly to adjust for the historical variations in the heat content of the gas distributed to our customers. Examples: In October 2018 the Variable Heat Content Factor was 1.0565. In January 2018 it was 1.0520.

Actual Monthly Heat Content Numbers - Download the Monthly Rate Schedule
The heat content is updated monthly and shown on our Monthly Rate Schedule.  
Heat Content

On the Utility Bill.

While both factors are used by the DPU to convert the CCF to Therms, only the elevation conversion factor is displaying on each customer’s utility bill under "Multiplier." Customers who are interested in obtaining the Actual Monthly Heat Content Numbers - Download the Monthly Rate Schedule. This schedule is updated each month. 

In our examples below we use a heat content factor of 1.054.

Example 1: White Rock Residential

Current Meter Read          159.00 CCF
Previous Meter Read          67.00 CCF
Difference                           92.00 CCF at approximately 6,500 feet
                                          =========

Elevation                         92.00 x 0.81 = 74.520 CCF at Sea Level
Heat Content/Therms     74.52 x 1.054 = 78.544 Therms


Example 2: Los Alamos Town Site Residential

Current Meter Read          159.00 CCF
Previous Meter Read          67.00 CCF
Difference                           92.00 CCF at approximately 7,300 feet
                                          =========

Elevation                         92.00 x 0.78 = 71.760 CCF at Sea Level
Heat Content/Therms     71.76 x 1.054 = 75.635 Therms

Example 3: White Rock Commercial with Higher than Standard Line Pressure

Current Meter Read          159.00 CCF
Previous Meter Read          67.00 CCF
Difference                           92.00 CCF at approximately 6,500 feet
                                          =========

Higher Line Pressure     92.00 x 1.146 = 105.432 CCF at 6,500 feet
Elevation                     105.432 x 0.81 = 85.399 CCF at Sea Level
Heat Content/Therms   83.291 x 1.054 = 90.011 Therms