Energy Management Systems – The Gas Bill

Energy Management Systems – Assessing Performance

Most plastics processing sites use gas simply for space heating but some processes use gas as part of the process, e.g., rotational molding.  

Where gas is used for hot water only then this is generally relatively constant over the year. For space heating, the gas use load will be related to the weather conditions (how cold it is) and the weather is then a ‘condition’ driver for gas use. 

Where gas use is part of the process then use will be driven by both the activity (production) and the condition (weather). The two drivers will need to be separated either by sub-metering or by statistical analysis – but sub-metering is preferable.  


  • Plot gas use against time. If it is used for space heating only then you should see peaks in winter and troughs in summer. 
  • Plot gas use against the ’heating degree-days’ in the month as a scatter chart. ‘Heating degree days’ is a measure of how cold it is in a specific area. There should be a linear relationship, the Performance Characteristic Line (PCL) for the heating system – if not then find out why. 
  • Use the PCL to assess heating system performance. 
  • If gas use is part of the process, then recording meters allow gas use to be related to production volume via a PCL – as with electricity use (ESTotM 5). 

Dr. Robin Kent is the author of ‘Energy Management in Plastics Processing’, published by Elsevier and Managing Director of Tangram Technology Ltd. ( ), consulting engineers for energy and sustainability management in plastics processing. 

Also read:

You can also learn more about energy management at Robin’s webinar, Energy Management in Plastics Processing, on Thursday, April 18, 2024.

By Robin Kent | April 16, 2024

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