exergyfactor.com — a free calculator for reporting energy as quantity plus quality.
A megawatt-hour is not a megawatt-hour. One MWh of electricity can do a full MWh of work. One MWh of 80 °C hot water, against a 20 °C environment, can do about 0.17 MWh of work — the rest cannot be recovered, no matter how good your equipment is. Add them up as "2 MWh" and the number is arithmetically fine and physically meaningless.
Energy reporting almost universally records the first law (how much) and discards the second (how useful). Decisions get made on the sum.
Report one extra field alongside the quantity:
1 MWh_th, fx = 0.170 [Th = 80 °C, T0 = 20 °C]
fx is the Exergy Factor: accessible work potential per unit of reported
energy, against a stated reference environment. It is nonnegative and can exceed
1 when the denominator is an accounting basis such as LHV. It is computed from
stated conditions rather than assumed, and it makes
electricity, fuels, heat, cooling, and storage comparable on the axis that
actually determines what they can do.
The reference environment is part of the report, not a hidden default — the same 80 °C heat quantity is worth more in winter than in summer, and the notation says so.
The distinction from that environment is what makes work possible. The
calculator reports it through fx; it does not apply a separate
"distinguishability factor." At the same state as the reference, fx = 0.
The static site behind exergyfactor.com. Zero build step, no dependencies,
served directly by GitHub Pages.
| Page | What it does |
|---|---|
index.html |
Single-record calculator producing full quantity-plus-quality notation |
compare.html |
Compares two energy forms by accessible exergy in MWh_ex |
methodology.html |
The thermodynamic basis, and the limits of the method |
api-key.html |
Inspect and use the public API contract |
Supported: typed carrier notation (MWh_e, MWh_th, MWh_solar,
MWh_HHV_NG), temperature-based thermal Exergy Factors, cooling services below
ambient, unit conversion for energy and accessible exergy, and the Carrier
Registry / Fidelity Tier summaries.
The browser unit selector includes SI energy units through PJ and TWh, customary BTU/MMBTU and therm units, refrigeration ton-hours for cooling, and named fuel volume shortcuts.
When the carrier and quality context are known, the calculator uses the full notation as its standard output:
5 BTU_th, fx = 0.214 [Th = 100 °C, T0 = 20 °C]
1.3 MWh_HHV_NG, fx = 0.930 [basis = HHV]
The short form (quantity typed_unit, fx = value) remains valid when the source
or reference context is unavailable. The typed suffix still matters: BTU_th
identifies thermal energy, while MWh_HHV_NG identifies natural gas on an HHV
denominator; a bare BTU or MWh leaves that carrier or basis implicit.
Fuel volumes cannot determine an exact energy quantity without a measured
heating value. The calculator keeps its scf(natural gas) and bbl(oil)
shortcuts tied to the matching fuel form and places the pinned EIA 2026
U.S.-average estimate in the Unit info tooltip; use the companion library with
a measured HHV or LHV for a composition-specific result.
The companion library also accepts Primary, Secondary, Final, and Useful Exergy boundaries alongside the corresponding energy records, then records Applied Exergy at the task and a separate non-energy service outcome. It preserves historical substitution-method data as a statistical equivalent without treating it as physical exergy. This additional accounting does not add complexity to the browser calculator.
| Product | Use it when |
|---|---|
| Exergy Factor | You need a free, no-install calculator for one or a few energy records. |
| Quantity and Quality | You need the canonical calculation kernel, CLI, schemas, API, or batch reporting standard. |
| The Exergy Imperative | You need to turn utility or telemetry data into prioritized losses, emissions, health screens, economics, and reports. |
The canonical framework paper is available at
paper/quantity-and-quality-standard-reporting-framework.pdf.
python -m http.server 8765Then open http://127.0.0.1:8765/.
Before publishing changes:
python scripts/check_site.py
node --check script.js
node scripts/check_calculations.jsThe site's reference examples are generated from the Python package, so the two cannot drift. From a checkout of quantity-and-quality, with this repo checked out alongside it:
python -m quantity_quality export-web-data \
--output ../exergy-factor/data/reference_examples.json \
--js-output ../exergy-factor/data/reference_examples.jsCommit the regenerated data/ files together with whatever library change
caused them to move.
The hosted public beta is keyless. Use the canonical endpoint:
https://api.exergyfactor.com/v1
The health check is:
https://api.exergyfactor.com/v1/health
Local previews use:
http://127.0.0.1:8000/v1/health
For local work, run the optional API service and use its corresponding local base URL instead.
The free deployment is intended for a low-volume public preview. It may sleep when idle and should not be treated as a high-availability or high-volume service.
This is a calculator for individual, accumulated energy quantities. It returns the quantity, Exergy Factor, and accessible exergy. It does not perform process, technology, emissions, health, or economic analysis; The Exergy Imperative handles that downstream work. The companion Python library offers an optional accounting record for Primary, Secondary, Final, and Useful Exergy, Applied Exergy at the task, and a separate non-energy service outcome. When total task-boundary energy is measured, the methodology also distinguishes its Applied Energy and Applied Anergy residual; this website does not add that complexity to the calculator.
The browser presets cover heat, electricity, cooling, mechanical work, common fuels, and solar radiation. Natural gas and hydrogen default to HHV, with LHV available when the source record explicitly uses it. Heterogeneous fuels and state-specific forms such as biomass, radiation, nuclear, and plasma use the library/API or the calculator's custom factor input rather than an invented universal preset.
If you use the Exergy Factor notation in published work, please cite the paper above. Citation metadata is in quantity-and-quality/CITATION.cff.