Fourth Power website screenshot

Fourth Power

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.

Fourth Power is profiled on the APIs.io network. Tagged areas include Company, Energy, Thermal Energy Storage, Grid Storage, and Long Duration Energy Storage.

🌐 Visit website 📡 Source on GitHub
3.3/100 minimal ▬ flat Agent 0/100 human only Full breakdown ↓
scored 2026-08-20 · rubric v0.12.0
0 APIs
CompanyEnergyThermal Energy StorageGrid StorageLong Duration Energy StorageClean EnergyRenewable EnergyThermophotovoltaicsClimate Tech

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-08-20 · rubric v0.12.0
Composite quality — 3.3/100 · minimal
Contract Quality 0.0 / 21
Developer Ergonomics 0.0 / 17
Access Clarity 0.0 / 17
Operational Transparency 0.0 / 11
Contract Governance 0.0 / 10
Discoverability 4.3 / 9
Regulatory Posture 1.2 / 15
Agent readiness — 0/100 · human only
Machine-Readable Contract 0 / 18
Agentic Access Contract 0 / 10
Documented Reversibility 0 / 6
MCP Server 0 / 12
Machine-Readable Auth 0 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 0 / 7
Typed Event Surface 0 / 6
Agent Skills 0 / 5
Well-Known Catalog 0 / 4
Consent & Bot Identity 0 / 3
A2A Agent Card 0 / 8
Dry-Run / Simulate Mode 0 / 4
Regulatory Posture applies to this provider. Its tags matched the Energy & Utilities regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.
The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/fourth-power: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

Security Posture 1

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Fourth Power Domain Security

TLSv1.3 · DMARC

SECURITY

Resources

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity
DomainSecurity

Company 1

The organization behind the API

Website
Website

Source (apis.yml)

apis.yml Raw ↑ 
aid: fourth-power
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source: []
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/fourth-power.png
name: Fourth Power
description: 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.
url: https://raw.githubusercontent.com/api-evangelist/fourth-power/refs/heads/main/apis.yml
x-type: company
x-source: vc-portfolio
x-website: https://gofourth.com/
x-backed-by:
- dcvc
x-tier: stub
x-tier-reason: portfolio-lead
specificationVersion: '0.23'
created: '2026-07-17'
modified: '2026-07-19'
tags:
- Company
- Energy
- Thermal Energy Storage
- Grid Storage
- Long Duration Energy Storage
- Clean Energy
- Renewable Energy
- Thermophotovoltaics
- Climate Tech
apis: []
common:
- type: DomainSecurity
  url: security/fourth-power-domain-security.yml
- type: Website
  url: https://gofourth.com/
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
x-enrichment:
  date: '2026-07-19'
  status: backfilled
  pass: local-v1
  note: backfilled from .gitignore signal + verified work evidence