Critical Load methodology
A place is constrained by the first physical infrastructure limit or environmental budget that reaches its limit.
Every value carries an evidence class.
| Class | Meaning | Example |
|---|---|---|
| Measured | Direct physical observation | GPU cumulative energy counter |
| Observed / reported | Operational or provider record | Cloud usage, facility PUE |
| Modelled | Estimated using versioned coefficients | Instance energy, facility embodied allocation |
| Contextual | Location/time environmental factor | Grid factor, basin stress |
| Derived | Critical Load calculation carrying upstream IDs | lifecycle gCO₂e / GPU-hour, water-limited MW |
Observe → contextualize → allocate → constrain → decide.
Observe
Physical telemetry, usage, manufacturing and site records.
Contextualize
Grid, watershed, climate, procurement and regulatory boundary.
Allocate
Move shared manufacturing and infrastructure impact to workload units.
Constrain
Estimate supportable compute under each physical or environmental budget.
Impact
Compare the place baseline with the proposed compute scenario and preserve the local deltas.
Decide
State the supportable envelope, binding limit, project conditions and alternatives.
Carbon starts before the accelerator exists and continues beyond electricity use.
CL-LC defines a compute lifecycle boundary spanning semiconductor manufacturing, hardware integration, facility construction, electricity, cooling, shared services, replacement and end of life.
| Layer | Included carbon sources | Typical denominator |
|---|---|---|
| Semiconductor | Fab electricity, process gases, abatement, chemicals, UPW, wafer/die yield, packaging | good die / packaged device |
| Hardware | Boards, servers, racks, memory, storage and supporting electronics | lifetime useful compute |
| Facility | Building, steel/concrete, UPS, transformers, switchgear, batteries, cooling plant | capacity × time × utilization share |
| Operation | IT electricity, facility overhead, backup generation and location-specific electricity context | workload energy / GPU-hour / job |
| Cooling | Cooling electricity when measured bottom-up, refrigerants, embodied cooling equipment | facility or workload allocation |
| Shared services | Network and storage attributable to the compute service | GB transfer / GB-hour / service share |
| Replacement / EOL | Component replacement and end-of-life treatment within the declared boundary | lifetime useful compute |
“Green electricity” is not automatically zero lifecycle carbon.
Critical Load keeps three electricity statements separate: physical location-based electricity, procurement or market-based claims, and lifecycle emissions of the generation assets themselves.
Location-based
What the local electricity system supplied in the stated time and place boundary.
Procurement-based
PPA, certificates and other contractual attributes remain a distinct claim rather than replacing the physical record.
Generation assets
Manufacturing, construction, maintenance and end-of-life emissions of electricity infrastructure where the study boundary requires them.
Shared infrastructure must be allocated before it can become compute carbon.
Useful-compute allocation
Lifetime, utilization, GPU-hours, delivered FLOPs or another declared useful-work denominator.
Capacity-time allocation
Facility embodied carbon is assigned by capacity, service life, IT load share and utilization.
Service allocation
Traffic, storage-hours or a documented service allocation connects shared infrastructure to the workload.
Each term is first normalized to the same useful-compute denominator and time boundary.
Boundary rules prevent the same carbon from being counted twice.
If facility electricity is estimated as IT energy × PUE, cooling electricity is already inside the facility total. A bottom-up cooling-energy record replaces that portion; it does not add to it.
If a lifecycle electricity factor already includes generation-asset construction, those assets are not added again as a separate term.
Semiconductor, package and system records are reconciled before aggregation.
CL-SCM carries fab evidence into the lifecycle model.
Fab process inventory → wafer basis → good-die allocation → advanced packaging → product carbon → lifetime useful compute. CL-SCM is the upstream manufacturing method feeding the broader CL-LC lifecycle carbon model.
Only after the full lifecycle intensity is normalized to the same time and capacity boundary does carbon enter the Critical Load minimum operator.