Understanding the Differences Between Higher Heating Value and Lower Heating Value in Efficiency Calculations

Topics Covered:

  • Understanding HHV and LHV Efficiency
  • What are HHV and LHV?
  • Differences in Efficiency Measurements
  • Why the Difference Matters
  • Choosing the Right Metric
  • Key Takeaways

 

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Author:

Don Betts, Product Manager, Packaged Firetube Boilers – Cleaver-Brooks

Excerpt:

Energy efficiency is a key consideration in fuel-based systems. Defining operating efficiency for a packaged boiler can vary based on the method used to calculate efficiency ratings. These differing calculation methods influence how energy performance is measured and compared. There are two common standards used to calculate fuel efficiency: Higher Heating Value (HHV) and Lower Heating Value (LHV).

Key Takeaways:

  1. HHV includes all energy content (even when lost to water vapor) and is typically used in North America.
  2. LHV, more popular in Europe, excludes energy lost to water vapor, often yielding a higher efficiency rating.
  3. HHV presumes all water in the combustion process is in a liquid state after combustion, and LHV presumes the water component of a combustion process is in a vapor state at the end of combustion. Or, simply stated, HHV includes energy from water vapor in the exhaust gases while LHV does not.
  4.  When calculating the total amount of boiler fuel usage, HHV should always be used. If LHV is used, the amount of fuel usage will be  underestimated.

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