Table of Contents
The K-index
A live planetary energy metric: where humanity actually stands on the Kardashev ladder, computed from data.
Back to the project hub.
Definition
K = (log10(P_avg in watts) − 6) / 10 (Sagan 1973)
P_avg = world total energy supply per year ÷ seconds in a year (1 TWh/yr = 1.1408×10^8 W average). K = 1 ⇔ 10^16 W ⇔ 10,000 TW average. Every +0.01 K = +26% power; every +0.1 K = ×10.
The current value
K = 0.728 (2025) — world total energy supply 600.3 EJ (Energy Institute Statistical Review 2026, via Our World in Data) ⇒ 19.02 TW average power.
- Basis disclosure: EI dropped its substitution method in 2025; on the older substitution basis the remaining climb reads ×526–×560 instead of ×525, and K = 0.725–0.728. We print the current basis and the spread.
- Data: OWID grapher
primary-energy-cons(CC BY — attribution: Our World in Data / Energy Institute; Smil pre-1965).
The series (world, selected years)
| Year | TWh/yr | Avg power | K | Note |
|---|---|---|---|---|
| 1800 | 97 | 0.01 TW | 0.404 | wood, water, muscle |
| 1850 | 569 | 0.06 TW | 0.481 | coal era begins |
| 1900 | 5,990 | 0.68 TW | 0.583 | |
| 1950 | 20,472 | 2.34 TW | 0.637 | postwar boom starts |
| 1970 | 54,921 | 6.27 TW | 0.680 | fastest K climb in history |
| 2000 | 105,981 | 12.09 TW | 0.708 | |
| 2010 | 136,245 | 15.54 TW | 0.719 | |
| 2020 | 147,985 | 16.88 TW | 0.723 | the stagnation decade |
| 2024 | 164,494 | 18.77 TW | 0.727 | matches EI 592 EJ ✓ |
| 2025 | 166,754 | 19.02 TW | 0.728 | current value |
Milestones (annual data from 1965): K=0.60 in 1910, 0.65 in 1960, 0.70 in 1988, 0.72 in 2011. The 0.6→0.7 decade took 78 years at 2.5–3.3%/yr growth; the same log-distance at 1%/yr would take ~230 years — the rate, not the physics, sets the calendar.
Per-country (v2)
- Only 3 countries ≥ 1 TW: China 5.14 TW (max national K = 0.671), US 2.97, India 1.24 — every polity is sub-planetary.
- China-2025 = world-1967 in energy terms (162.2 EJ vs 163.7 EJ) — the energy time machine.
- Top-10 countries = 69.8% of world energy; per-capita spread ×64; 32% of humanity below 1 kW/person.
- China = 42% of world energy growth 2024→25.
Sources and mirrors
Master files: knowledge/04 (world series) and knowledge/08 (per-country) in the project repo; the appendable public mirrors are linked from the hub artifact table. Corrections welcome in any mirror's APPEND LOG.
