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Koomey's law

The empirical trajectory by which computations delivered per joule dissipated have doubled about every 1.57 years (slowing to ~2.6 after Dennard scaling broke in 2005), tracking the energy cost of a logical operation toward the Landauer floor.

Core Idea

Koomey's law is the observation that computations delivered per joule dissipated doubled roughly every 1.57 years from the mid-1940s to about 2000, slowing to about 2.6 years after Dennard scaling broke down around 2005. Where Moore's law tracks transistor density, Koomey's law tracks the energy cost of a logical operation — how cheaply each switching event can be performed. During Dennard scaling the mechanism was feature shrinkage and voltage reduction; after, it shifted to architectural specialization. It has a hard thermodynamic floor: Landauer's kT ln 2 per irreversible bit erasure.

Scope of Application

Koomey's law lives entirely within computing — across the hardware, infrastructure, and systems subfields where the energy cost of a logical operation is the design variable.

  • Semiconductor roadmapping — the curve set as a per-generation efficiency target (ITRS, IRDS).
  • Data-center and IT-infrastructure planning — efficiency versus workload growth setting aggregate demand.
  • Mobile, wearable, and embedded design — the feasibility threshold for battery-limited products.
  • AI cost-of-training and edge inference — dating when a model class ships at watt-scale power.
  • Computer-architecture analysis and ICT environmental policy — the orthogonal energy-per-operation axis.

Clarity

Naming Koomey's law separates how much computing a chip delivers from how cheaply per joule it delivers it. Against the count-and-speed axis a stalled-clock era looks like progress halting; the energy axis shows it still improving by orders of magnitude. It makes the 2005 regime break legible as an efficiency slope change and locates the trajectory against a thermodynamic floor rather than lithographic ceilings.

Manages Complexity

The full stack of what makes a battery-powered product feasible — node, voltage, microarchitecture, cooling, workload, battery — collapses into one exponential in computations per joule, summarized by two scalars: current energy-per-operation and doubling time. Projecting the curve reads off feasible-now, feasible-in-N-doublings, or never, with a known regime break at 2005 and a fixed Landauer endpoint.

Abstract Reasoning

It supports feasibility forecasting (convert "is this buildable?" into a date), slope-selection and regime diagnosis around the 2005 break, axis-decomposition (separate "stopped getting faster" from "stopped getting efficient"), floor-bounded extrapolation against Landauer's kT ln 2, and an aggregate-consumption inference coupling efficiency to workload growth.

Knowledge Transfer

Within computing Koomey's law transfers as a working trend-line wherever the energy axis of silicon is the binding constraint — the same observable, floor, and slope-selection discipline carry across roadmapping, data-center planning, embedded design, and AI projection. Beyond computing, "a Koomey's law for X" is analogy, borrowing the shape while dropping Dennard scaling and the thermodynamic bound. The genuinely portable skeleton was never Koomey-specific: it is carried by exponential_growth, learning_curve_effects (Wright's law), and physical_limits, with Landauer's bound merely computing's value of the floor.

Relationships to Other Abstractions

Local relationship map for Koomey's lawParents appear above the current abstraction, mutual partners to the right, and children below. Node labels state whether each abstraction is prime or domain-specific; colors identify relation types.Koomey's lawDOMAINPrime abstraction: Irreducible Floor — is part ofIrreducibleFloorPRIMEPrime abstraction: Exponentiation — is a decomposition ofExponentiationPRIME

Current abstraction Koomey's law Domain-specific

Parents (2) — more general patterns this builds on

  • Koomey's law is part of Irreducible Floor Prime

    Koomey's Law contains an Irreducible Floor because Landauer's thermodynamic cost per irreversible bit erasure bounds the total efficiency gain remaining under the law's computational premise.

  • Koomey's law is a decomposition of Exponentiation Prime

    Koomey's Law extracts Exponentiation because computations delivered per joule follow an empirical doubling-time trajectory whose slope can be measured separately before and after a regime break.

Hierarchy paths (3) — routes to 3 parentless roots

Neighborhood in Abstraction Space

Koomey's law sits in a sparse region of the domain-specific corpus (91st percentile for distinctiveness): few abstractions share its structure, so a faithful description tends to retrieve it precisely.

Family — Unclustered & Miscellaneous (309 abstractions)

Nearest neighbors

Computed from structural-signature embeddings · 2026-07-12