Fourth Power
Fourth Power is a Cambridge, MA-based energy storage startup developing utility-scale thermal batteries that store electricity as heat in carbon blocks via molten tin and convert it back using thermophotovoltaic cells, targeting electric utilities, data centers, and industrial facilities with low-cost, long-duration storage ahead of 2028 commercial deployment.
- Company typePrivate
- Founded2023
- HeadquartersCambridge, United States
- Headcount11–50
- GTM typeB2B
- OfferingHardware or Manufacturing
What Fourth Power does
Fourth Power is a Cambridge, Massachusetts-based energy storage startup that has developed a utility-scale thermal battery system designed to provide flexible-duration electricity storage at costs targeted below $25/kWh at scale. The company's core technology stores electricity as heat by heating molten tin to extreme temperatures (up to 2,400°C / 4,350°F) using inexpensive carbon blocks as the storage medium, then converts the heat back to electricity via proprietary thermophotovoltaic (TPV) cells achieving over 40% conversion efficiency. The modular architecture separates energy and power subsystems, allowing storage duration to scale independently from 5 hours to 100+ hours within a compact 1-acre footprint for a 100MW, 10-hour system. The technology was developed over 10+ years of R&D at Georgia Tech and MIT, largely funded by U.S. Department of Energy grants, and engineered for 30+ year operational life using corrosion-resistant graphite and tin.
Fourth Power operates a direct enterprise sales motion targeting electric utilities, grid operators, data center operators, and industrial facilities requiring long-duration energy storage. Revenue will derive from hardware sales of utility-scale thermal energy storage systems and potentially long-term service agreements, with commercial deployment targeted by 2028 and demonstration projects ongoing in 2025. The company is currently commissioning a 1 MWh-e integrated demonstration system ahead of commercial launch. Fourth Power has raised a total of $45 million across a $19 million Series A in December 2023 (led by DCVC with Breakthrough Energy Ventures and Black Venture Capital Consortium) and a $20 million Series A Plus in September 2025 (led by Munich Re Ventures with DCVC and BEV participation). The company secured a 47,500-square-foot manufacturing facility lease in Bedford, Massachusetts in late 2024 to support commercial-scale production. The leadership team combines founder/chief technologist Dr. Asegun Henry (MIT professor), CEO Arvin Ganesan (former Apple global energy and environment policy head), and senior executives recruited from Tesla, Rivian, Ambri, Equilibrium Energy, PG&E, and Edison Energy.
Fourth Power firmographics
Firmographics- Name
- Fourth Power
- Legal name
- Fourth Power, Inc.
- Website
- https://gofourth.com
- Company type
- Private
- Founded year
- 2023
- Operating status
- Operating
- Headcount range
- 11–50 employees
- Short description
- Fourth Power is a Cambridge, MA-based energy storage startup developing utility-scale thermal batteries that store electricity as heat in carbon blocks via molten tin and convert it back using thermophotovoltaic cells, targeting electric utilities, data centers, and industrial facilities with low-cost, long-duration storage ahead of 2028 commercial deployment.
- Ownership category
- akta.pro rank
Fourth Power industry classification
Industry- Product category
- Thermal Energy Storage Systems
- NAICS
- Power Boiler and Heat Exchanger Manufacturing (33241), Heating Equipment (except Warm Air Furnaces) Manufacturing (333414), Electric Power Generation (22111)
- SIC
- Industrial Process Furnaces & Ovens (3567), Heating Equipment, Except Electric & Warm Air Furnaces (3433), Pumps & Pumping Equipment (3561)
- akta.pro primary industry
- Thermal LDES (High-Temperature, Molten Salt, Carnot/Heat-to-Power) (EUAFADAC)
- akta.pro secondary industries
- High-Temperature Solid Media Storage (Bricks, Concrete, Ceramic) (EUAFANAF), Molten Salt Thermal Storage (CSP & High-Temperature Heat) (EUAFANAB)
Keywords
Where Fourth Power is headquartered
LocationHeadquarters
- HQ city
- Cambridge
- HQ country
- United States
- HQ region
- North America
Offices3 records
Markets served
Fourth Power business model
Business model- GTM type
- B2B
- Offering type
- Hardware or Manufacturing
- Cost components
- Technology or R&D, Personnel, Infrastructure, Supply Chain, Operations, Marketing or Sales
Revenue model
- Utility-Scale Thermal Energy Storage Systems: Fourth Power plans to sell or provide utility-scale thermal energy storage systems to grid operators and utilities. The company targets full commercial deployment by 2028, with demonstration projects ongoing in 2025. Revenue will come from system sales and potentially long-term service agreements.
- Grid Services and Storage Capacity: Provides flexible-duration energy storage capacity to utilities, allowing them to add storage duration incrementally. The modular nature allows utilities to start with 5-hour storage and expand as needed.
Go-to-market motion1 record
Distribution channels1 record
Marketing channels6 records
Fourth Power product offering
Product offeringCore offering
Fourth Power designs, manufactures, and sells utility-scale thermal energy storage systems that store electricity as heat in carbon blocks heated to extreme temperatures (up to 2,400°C) using molten tin as the heat transfer medium. The proprietary thermophotovoltaic (TPV) power sticks convert the stored high-temperature heat back into electricity on demand, enabling flexible-duration storage from 5 to 100+ hours for electric utilities, grid operators, data centers, and industrial facilities.
Product overview
Fourth Power offers a unified thermal energy storage system comprising three core components: a modular thermal energy storage system using molten tin heated to 2,400°C stored in carbon blocks, TPV power sticks for conversion back to electricity, and supporting demonstration systems for durability testing. The modular architecture allows scaling from 5 hours to 100+ hours of storage duration, with full-scale installations planned at 25 MW/250 MWh capacity. The company is currently commissioning a 1 MWh-e integrated demonstration system ahead of commercial deployment.
Differentiator
Problem solved
Functional benefit
Products and services
- Modular Thermal Energy Storage System
Quantifiable outcome
- Target cost of $25/kWh at scale
- +6 more outcomes
Companies that use Fourth Power
Customer profileNamed customers2 records
Segments3 records
Ideal customer profiles3 records
Fourth Power technology and API
TechnologyTechnology focussed Yes
API detail
- Has API
- No
- API docs
- API detail
Core technology
AI maturity
App detail
Feature5 records
Fourth Power partnerships and signals
Strategic signalPartnerships
Two partnerships are on record, tiered minor.
- Camber DevelopmentminorOwner of the manufacturing complex at 44 Middlesex Turnpike in Bedford, MA where Fourth Power secured its 47,500-square-foot lease for advanced manufacturing.
- NewmarkminorCommercial real estate firm that arranged the lease for Fourth Power's 47,500-square-foot manufacturing facility in Bedford, MA.
Scale indicators10 records
Recent moves7 records
Expansion highlights4 records
Fourth Power competitors and assessment
Company assessmentDirect peers
- Antora Energy: Antora Energy builds utility-scale thermal batteries using thermophotovoltaic cells and carbon block storage, an architecture nearly identical to Fourth Power's molten tin / TPV / carbon approach. Both target utility LDES customers and overlap heavily on technology, customers, and go-to-market.
- Malta Inc. Malta develops a pumped heat energy storage system that stores electricity as heat in molten salt and cold in an antifreeze-like fluid, then converts it back to power. It is one of the closest long-duration thermal storage peers to Fourth Power's grid-scale thermal battery.
- Rondo Energy: Rondo Energy supplies industrial heat batteries that store renewable energy as high-temperature heat for industrial process use. Fourth Power targets overlapping industrial decarbonization customers and competes in the same high-temperature thermal storage category.
- Brenmiller Energy: Brenmiller Energy produces thermal energy storage systems (bCRUSITHERM) using crushed rock and other solid media for industrial and utility customers. It is a direct competitor in grid-scale and industrial thermal storage for decarbonization.
- Form Energy: Form Energy develops iron-air batteries for multi-day grid storage and is one of the most heavily funded LDES competitors. It targets the same utility customers and 100+ hour storage use case that Fourth Power addresses with thermal storage.
- Highview Power: Highview Power commercializes liquid air energy storage (CRYOBattery) for long-duration grid applications. It is a direct LDES peer to Fourth Power in addressing utility-scale, multi-hour storage demand.
- Eos Energy Enterprises: Eos Energy Enterprises produces zinc-based long-duration battery systems for utility and commercial customers. It competes with Fourth Power for the same multi-hour utility storage procurement budgets.
Broad incumbents
- Energy Vault: Energy Vault offers multiple long-duration storage technologies (gravity, battery hybrids, and thermal) targeting utilities and grid operators. It is a broader incumbent in LDES that overlaps with Fourth Power on utility-scale storage customers even though its core gravity and hybrid approaches differ.
Emerging players
- Ambri: Ambri develops liquid metal batteries using calcium and antimony for long-duration storage. It overlaps with Fourth Power on liquid-metal-based grid storage and shares executive alumni (Alex Elliott, Fourth Power's EVP of Engineering, was previously EVP of Engineering at Ambri).
- Polar Night Energy: Polar Night Energy builds sand- and solid-media-based thermal energy storage systems for district heating and industrial customers. It is an emerging peer in the high-temperature thermal storage category relevant to Fourth Power.
Market position
Strengths4 records
Weaknesses5 records
Competitive moat5 records
Key risks6 records
Key highlights6 records
Customer concentration
Fourth Power social profiles
Digital presenceFourth Power financial estimates
Financial estimateRevenue estimate
Valuation estimate
Fourth Power leadership team
Management profileNumber of profiles
Profiles16 records
Fourth Power funding detail
Funding detailFunding overview
Funding rounds2 records
Investors4 records
Funding detail is available on the Subscription and Enterprise plan.Contact sales →
Fourth Power M&A and investment
M&A and investmentM&A
Investments
M&A and investment is available on the Subscription and Enterprise plan.Contact sales →
Frequently asked questions about Fourth Power
What does Fourth Power do?
Fourth Power designs, manufactures, and sells utility-scale thermal energy storage systems that store electricity as heat in carbon blocks heated to extreme temperatures (up to 2,400°C) using molten tin as the heat transfer medium. The proprietary thermophotovoltaic (TPV) power sticks convert the stored high-temperature heat back into electricity on demand, enabling flexible-duration storage from 5 to 100+ hours for electric utilities, grid operators, data centers, and industrial facilities.
Is Fourth Power a public or private company?
Fourth Power is a private company. It is classified as venture growth investor backed and is currently operating.
When was Fourth Power founded?
Fourth Power was founded in 2023. It employs 11 to 50 people.
Where is Fourth Power based?
Fourth Power is headquartered in Cambridge, United States, in the North America region.
How does Fourth Power make money?
Two revenue lines are on record. Utility-Scale Thermal Energy Storage Systems are the primary driver. The others are grid Services and Storage Capacity.
Who are Fourth Power's main competitors?
Direct peers on record are Antora Energy, Malta Inc., Rondo Energy, Brenmiller Energy, Form Energy, Highview Power and Eos Energy Enterprises. Energy Vault is listed as a broad incumbent. Emerging players are Ambri and Polar Night Energy.
Does Fourth Power have an API?
No public API is recorded for Fourth Power.
What industry is Fourth Power in?
Fourth Power's product category is Thermal Energy Storage Systems. Its primary akta.pro industry code is EUAFADAC, Thermal LDES (High-Temperature, Molten Salt, Carnot/Heat-to-Power), with a secondary code of EUAFANAF, High-Temperature Solid Media Storage (Bricks, Concrete, Ceramic). Its NAICS code is 33241 and its SIC code is 3567.