The K-index

The K-index

A live planetary energy metric: where humanity actually stands on the Kardashev ladder, computed from data.

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.