HVAC Ductwork, Air Handling & Mechanical Products worked example

Energy Rating Margin with achieved energy efficiency rating of 2.95 units: a worked example

What does the result look like when achieved energy efficiency rating reaches 2.95 units? The full calculation is worked below with real intermediate numbers. Use this when verifying that an air handling unit or packaged HVAC system meets the minimum efficiency requirement specified in ASHRAE 90.1, AHRI standards, or a project specification. Energy ratings for air handlers may be expressed as fan energy index (FEI), integrated energy efficiency ratio (IEER), or specific fan power (SFP in W per L/s). Checking the margin above the minimum ensures the selected equipment is compliant and shows how much headroom exists before the limit is reached.

The inputs for this scenario

  • Achieved energy efficiency rating: 2.95 units (raised for this scenario; the documented default is 1.18)
  • Minimum required rating (code or spec): 1 units (unchanged)
  • Reference value for margin calculation: 1 units (unchanged)

Working through the calculation

  • Applying the documented formula (Energy rating margin = achieved rating - minimum required rating) to the inputs above produces each figure below.
  • At this operating point the engine returns 195 % for margin, the number this scenario is built around.
  • At this operating point the engine returns 1.95 value for absolute margin.
  • At this operating point the engine returns 2.95 value for available amount.
  • At this operating point the engine returns 1 value for required amount.

How this compares with the baseline

  • Against the tool's baseline example, where achieved energy efficiency rating sits at 1.18 units and the headline result is 18 %, this scenario comes in 983% above the baseline at 195 %.
  • A figure at this level is achievable when achieved energy efficiency rating is genuinely sustained, not just peaked for a shift. It is a single-point margin against one rating figure; it does not capture part-load performance, test uncertainty bands or field degradation, so a positive margin still needs validation against rated-condition tolerances.

Results at a glance

  • Margin: 195 % (headline result)
  • Absolute margin: 1.95 value
  • Available amount: 2.95 value
  • Required amount: 1 value

Run it with your numbers

  • Every input above is editable in the live Energy Rating Margin calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.