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 stream 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 quantity, fx = value |
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 |
Use the public API and open its interactive documentation |
Supported: typed carrier notation (MWh_e, MWh_m, MWh_th, MWh_solar,
MWh_HHV_NG), an HHV/LHV basis toggle for supported combustible fuels,
temperature-based thermal Exergy Factors, cooling services below ambient, unit
conversion for energy and accessible exergy, and the Carrier Registry / Fidelity
Tier summaries.
Fuel volumes cannot determine an exact energy quantity without a measured
heating value. The calculator labels its scf(natural gas) and bbl(oil)
shortcuts as pinned EIA 2026 U.S.-average estimates; 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 energy boundaries. 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 public beta API is keyless and available at:
https://exergy-factor-api.onrender.com/v1
Interactive documentation is at
https://exergy-factor-api.onrender.com/docs. A health check and sample
calculation are available from the API page on the website. The service
retains the same units, reference conditions, bases, boundaries, Fidelity Tiers,
assumptions, and warnings as the Python package. Free hosting may sleep after
inactivity; use the local package or deploy the container under your control for
production workloads.
This is a calculator for individual energy streams. 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 energy, Applied Exergy at the task, and a separate non-energy service outcome; this website does not add that complexity to the calculator.
If you use the Exergy Factor notation in published work, please cite the paper above. Citation metadata is in quantity-and-quality/CITATION.cff.