---
type: claim
domain: energy
description: "NIF achieved Q-scientific of 4 but Q-wall-plug of 0.01 — practical fusion requires Q-scientific of 10-30+ before engineering breakeven is reachable, and no facility has achieved Q-engineering greater than 1"
confidence: likely
source: "Astra, fusion power landscape research February 2026; Proxima Fusion Q analysis"
created: 2026-03-20
challenged_by: ["CFS SPARC targeting Q~11 may be sufficient for engineering breakeven at ARC given efficient power conversion"]
---

# The gap between scientific breakeven and engineering breakeven is the central deception in fusion hype because wall-plug efficiency turns Q of 1 into net energy loss

Understanding fusion claims requires distinguishing three levels of breakeven:

**Q(scientific) > 1:** Fusion energy output exceeds heating energy input to the plasma. NIF achieved this in December 2022 (Q=1.5) and has since reached Q=4.13 (April 2025, 8.6 MJ from 2.08 MJ laser energy). SPARC targets Q>2 (models predict Q~11). This is the metric companies announce.

**Q(engineering) > 1:** Electrical energy produced exceeds ALL electrical energy consumed by the facility — magnets, heating systems, cooling, cryogenics, controls, diagnostics, tritium processing. No facility has achieved this. The gap is enormous: NIF's lasers consume ~300 MJ of electricity to produce ~2 MJ of laser light, giving a wall-plug Q of approximately 0.01.

**Q(commercial):** Energy revenue exceeds all costs — capital amortization, fuel, operations, maintenance, grid connection, component replacement. No facility has come close.

Most analysts believe Q(scientific) of 10-30+ is required before Q(engineering) > 1 becomes achievable, depending on heating and power conversion efficiency. ITER's Q=10 target was designed specifically to explore this boundary, but ITER will never generate electricity — it has no power conversion systems.

Every "fusion breakeven" headline should be interrogated: which Q? NIF's ignition was genuinely historic — but it is 2-3 orders of magnitude from engineering breakeven.

## Challenges

CFS's SPARC targeting Q~11 may be sufficient for engineering breakeven at ARC if power conversion and plant systems are efficient enough. The compact tokamak design reduces parasitic loads (smaller magnets, less cryogenic cooling) compared to ITER-scale devices. But no one has demonstrated the full chain from plasma energy to grid electricity, and the gap between Q-scientific and Q-engineering is where most optimistic fusion timelines go to die.

---

Relevant Notes:
- [[Commonwealth Fusion Systems is the best-capitalized private fusion company with 2.86B raised and the clearest technical moat from HTS magnets but faces a decade-long gap between SPARC demonstration and commercial revenue]] — SPARC's Q~11 target addresses the Q-scientific threshold but Q-engineering remains unproven
- [[knowledge embodiment lag means technology is available decades before organizations learn to use it optimally creating a productivity paradox]] — the lag between plasma physics demonstrations and commercial power plants
- [[industry transitions produce speculative overshoot because correct identification of the attractor state attracts capital faster than the knowledge embodiment lag can absorb it]] — conflation of Q-scientific with Q-engineering creates fertile ground for hype cycles

Topics:
- energy systems
