Why does the loading basis matter?
The 2017 ENERGY STAR buyer guide hosted by the US Department of Energy distinguishes losses associated with energizing the core from winding losses that vary with loading. Its discussion explains why the operating load matters when assessing transformer efficiency.
RFQ Templates is independent and is not affiliated with ENERGY STAR or the Department of Energy. This dated guide supplies background, not a statement of current regulatory minimums, product eligibility or the correct transformer for a project.
Which fields should each supplier complete?
Keep the same approved technical scope before comparing loss figures. Ask for the actual manufacturer test or guaranteed-data basis required by the RFQ, rather than extract a number from a different product size.
| Comparison field | Supplier evidence | Unmatched basis to flag |
|---|---|---|
| Equipment | Exact rating and configuration | Different proposed variants |
| No-load loss | Stated watts and conditions | Unidentified reference basis |
| Load loss | Stated load point and reference conditions | Rated versus partial load |
| Efficiency | Load, power factor and calculation basis | One unexplained percentage |
| Operating profile | Project-approved assumptions | Full load assumed all year |
| Commercial assessment | Approved method and reviewer | Savings asserted without a model |
How can the larger efficiency number mislead?
Illustrative example. A fictional quote reports efficiency at one loading point, while a competing quote reports it at another. The bid sheet sorts the percentages and declares the larger value the lowest operating cost. The two figures have not established a like-for-like comparison.
The buyer requests matched data and applies the project's approved assessment method. Neither a loading profile nor an energy tariff is invented to force a result. Even matched transformer loss data does not establish whole-facility consumption or an equipment-life guarantee.
What should remain outside a simple quote ranking?
Record loading profile, energised hours, tariff basis, evaluation period and any authorized economic assumptions separately if an ownership-cost assessment is required. The responsible technical and commercial reviewers must approve that model and assess other specification requirements.
Do not use this worksheet to relax current rules, change specified ratings or approve a substitution. Engineering sign-off is performed only by the registered engineer on the job.
Common questions
What else should the bid team know?
Is the highest quoted percentage automatically the lowest operating cost?
No. Align conditions and use an approved operating and evaluation basis.
Does a dated buyer guide establish current legal minimums?
No. Check the applicable current requirements separately.
Does the sheet supply a tariff or saving?
No. Those need approved project evidence.
Primary sources
- ENERGY STAR: Guide to Buying More Energy Efficient Distribution Transformers, 27 September 2017ENERGY STAR and US Department of Energy