# Fourth Power

**Canonical:** https://apis.io/providers/fourth-power/  
**Website:** https://gofourth.com/  
**APIs profiled:** 0

Fourth Power is a grid-scale thermal energy storage company building a "thermal battery" that stores electricity as heat. Surplus wind and solar power is used to heat blocks of graphite to roughly 2,400 degrees Celsius; molten tin, circulated by an all-ceramic pump, moves that heat in and out of storage, and thermophotovoltaic (TPV) cells convert the stored heat back into electricity when the grid needs it. The company positions the system as a cheaper, longer-duration alternative to lithium-ion for firming a clean grid, and operates a megawatt-scale demonstration facility near Boston. Fourth Power raised a Series A led by DCVC in 2023. This is a company profile in the API Evangelist network; Fourth Power is a hardware and energy company and does not publish a public developer API.

## Kin Score — 3.3 / 100 (minimal)

Scored 2026-08-20 under rubric 0.12.0. Trend: flat (+0.0 from 3.3).

| Facet | Score |
|---|---|
| Discoverability | 50.0 |
| Contract Quality | 0.0 |
| Governance | 0.0 |
| Contract Governance | 0.0 |
| Operational Transparency | 0.0 |
| Developer Ergonomics | 0.0 |
| Commercial Clarity | 0.0 |
| Access Clarity | 0.0 |

Regulatory layer — **Energy & Utilities**: 8.1 (matched via tags).

## Agent readiness — 0.0 (human-only)

| Dimension | Value |
|---|---|
| Spec Presence | no |
| Agentic Access | no |
| Reversibility Documented | no |
| MCP Server | no |
| Auth Clarity | no |
| Idempotency | no |
| Error Semantics | no |
| OpenAPI Examples | no |
| Rate Limit Signal | no |
| Event Surface Described | no |
| Agent Skills | no |
| Well Known Catalog | no |
| Consent Identity | no |
| Agent Card | no |
| Dry Run Mode | no |

## Access

Unknown — onboarding: unknown, pricing: unknown, trial: no (confidence: low).

## Security (1)

- **Fourth Power Domain Security** — TLSv1.3 · DMARC

## Tags

Company, Energy, Thermal Energy Storage, Grid Storage, Long Duration Energy Storage, Clean Energy, Renewable Energy, Thermophotovoltaics, Climate Tech

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/providers/fourth-power/). Scores are computed from the provider's own public artifacts under a published rubric.