~99%
Share of the year a GEO collector is in sunlight
Short eclipses only around the equinoxes, up to ~72 minutes a day
Setcoin Intelligence · Space Infrastructure · Energy · Updated October 2026
Space-Based Solar Power: Physics, Costs and the Path to Firm Power from Orbit
Could solar power collected in orbit and beamed to Earth supply firm, clean electricity at a competitive cost, and what would have to fall for it to? Ninety-eight chapters on beam physics, efficiency, mass, launch, assembly, cost, markets, regulation and safety, built on agency studies, demonstration results, company disclosures and Setcoin's own cost model.
Open to everyone: the first 3 chapters in full, with exhibits and models; a free account adds their Excel models. Space subscription: all 101 chapters, every model and Excel file, 7-day free trial, then €199 a month. Already a reader? Sign in.
- Chapters
- 98 + 3 appendices · 180 min
- Interactive Models
- 5, with Excel
- Data
- NASA OTPS; ESA; DARPA; Lazard 2025; companies; launch records
- Figures As Of
- 27 October 2026
- ~$357
- Per MWh, Setcoin reference cost
- ~92%
- Launch share of capital
- ~18%
- Sunlight that reaches the grid
- 180 min
- Read, 98 chapters
In short
The physics of space-based solar power works; the economics do not yet. A collector in geostationary orbit is lit about 99% of the year, and power has been beamed wirelessly in orbit (Caltech, 2023) and by laser over 8.6 km on the ground (DARPA, 2025). But only about 18% of the sunlight collected reaches the grid with microwaves, and a 2 GW plant at 10 kg per kilowatt weighs about 20,000 tonnes, needing some 200 heavy launches. On Setcoin's reference ($1,000/kg launch, $2/W hardware) power costs about $357/MWh, with launch 92% of capital; at $200/kg it falls to about $95/MWh. Space hardware at hundreds of dollars a watt is the second gap. Early customers are defence, remote sites and data centres, not grids.
01 · The answer
The physics works. The bill is for launch, then for hardware.
A solar collector in geostationary orbit is lit about 99% of the year, against roughly a quarter of the time for good ground solar. Beaming the power down is proven at small scale: Caltech beamed power wirelessly in orbit in 2023, and DARPA sent more than 800 watts by laser over 8.6 km on the ground in 2025. Diffraction sets the size: a 1 km transmitter at 5.8 GHz makes a spot about 4.5 km across from geostationary orbit.
Most of the energy is lost on the way. In Setcoin's reference microwave chain about 18% of the sunlight collected reaches the grid; with lasers about 5.5%. That makes plants large. At 10 kg in orbit per kilowatt delivered, a 2 GW plant weighs about 20,000 tonnes, roughly fifty space stations, and needs about 200 launches of 100 tonnes.
Launch dominates the cost. At $1,000 per kilogram to low orbit and $2 per watt of hardware, Setcoin's model gives about $27 per watt of capital, 92% of it launch and orbit transfer, and about $357 per MWh. At $200 per kilogram the cost falls to about $95 per MWh; with half the mass and $1-per-watt hardware, to about $50. Qualified space hardware costs hundreds of dollars a watt today, so hardware is the second gap.
The first buyers will pay for something other than cheap energy: defence bases and remote sites that value delivered power, data centres that want round-the-clock clean supply, and satellites in orbit. Meta reserved up to 1 GW from Overview Energy in April 2026. Setcoin sees gigawatt plants on grids in the 2040s at the earliest, and only if launch, mass and hardware cost all fall together.
The study, chapter by chapter
98 chapters + 3 appendices · 180 min · updated 2026-10-27
- Executive Summary and Reading Guide
- What Space-Based Solar Power Is, and Is Not
- Key Numbers at a Glance
- Fifty-Eight Years of an Idea
- A Plant on One Page: a Worked 2 GW Example
- Why Now?
- Lessons from the 1979 Reference System
- Method: How Setcoin Assesses Space Solar Power
- Sunlight in Orbit: the Basic Advantage
- Concepts Compared: CASSIOPeiA, SPS-ALPHA, Tiles and Mirrors
- CASSIOPeiA in Detail
- Europe: ESA's SOLARIS Programme
- SPS-ALPHA and Modular Concentrators
- The United Kingdom: Studies, Competitions and Space Solar
- The United States: NASA, Caltech, AFRL and DARPA
- Caltech's Space Solar Power Project in Detail
- Japan: Decades of Research and OHISAMA
- Other National Programmes: Korea, India and Beyond
- China: a National Roadmap to Gigawatts
- Europe's Industry Base for Space Solar Power
- The Companies
- Case Study: the Meta–Overview Energy Agreement
- Demonstrations So Far
- What a First Orbital Demonstrator Should Prove
- Beam Physics: Why Antennas Must Be Large
- The Ionosphere and the Upper Atmosphere
- The Efficiency Chain: Microwave Systems
- Inside the Transmitter: Amplifiers, Antennas and Heat
- Laser Power Beaming
- Laser Receivers: Photovoltaics Tuned to Light
- Mirrors and Near-Infrared: Lighting Existing Solar Farms
- Microwaves or Lasers? A Side-by-Side Comparison
- Rectennas and Land Use
- Offshore Rectennas
- Safety: Beams, Birds, Aircraft and Eyes
- Health Evidence on Microwave Exposure
- Spectrum and the ITU
- Radio Astronomy and Other Spectrum Users
- Weather and the Atmosphere
- Beam Control: How a Phased Array Points Itself
- Mass and Specific Power
- Solar Cells for Space Solar Power
- Launch Requirements: Building a Plant in Orbit
- The Launch Market Space Solar Power Would Create
- Assembling Gigawatts in Orbit
- Assembly in Orbit: What Has Been Done So Far
- Hardware Cost: the Second Gap
- The Supply Chain for a Gigawatt
- Geostationary or Low Orbit?
- Other Orbits: Medium Orbit, Elliptical Orbits and Low-Orbit Constellations
- Operations, Servicing, Life and Debris
- Thermal Management: Getting Rid of Waste Heat
- The Cost of Electricity: Setcoin's Model
- Space Solar or Ground Solar with Wires and Storage?
- Reconciling Published Cost Estimates
- Learning Curves: What Solar Panels and Rockets Teach
- Firm Power on Earth: the Real Competition
- The Cost of the First Plant
- The Break-Even Map
- If Launch Became Almost Free
- What Drives Cost: Sensitivities and Learning
- Inside the Reference Plant's Costs
- The Value of Firm, Movable Power
- Public Money So Far
- Financing a First Plant
- Insurance and Risk Transfer
- Carbon and Lifecycle Emissions
- Building with Lunar Materials
- Defence and Remote Power: the First Paying Customers
- Power Beaming for the Moon and Mars
- Data Centres and Round-the-Clock Clean Power
- Mines, Industrial Sites and Off-Grid Industry
- Islands, Remote Grids and Disaster Relief
- Hydrogen and Fuels from Space Solar Power
- Power for Satellites: a Market in Orbit
- Grid Integration and Power Markets
- Regulation: Who Licenses a Power Beam?
- International Law and Security Concerns
- Environmental Effects Beyond Carbon
- Public Acceptance
- Skills and Workforce
- Scenarios to 2050
- Three Plants: Pilot, Commercial and Mature
- Roadmap: Milestones from 2026 to 2040
- Designing a Public Programme: Stage Gates
- What Would Have to Be True
- Common Misconceptions
- The Case For and Against
- A Timeline of Space Solar Power
- Lessons from Other Energy Technologies
- Space Solar Power and Fusion: Two Long Bets Compared
- Due-Diligence Checklist
- Implications by Reader
- Risk Register
- How This Study Connects to the Space Research Programme
- Signals to Watch
- Twenty Questions This Study Answers
- Methodology and Sources
- Appendix A: Programme and Demonstration Reference Table
- Appendix B: Glossary
- Appendix C: Setcoin Reference Data
02 · The evidence
Four Numbers Behind the Verdict
>800 W
Beamed by laser over 8.6 km on the ground
DARPA POWER record, 2025; grid plants need about two million times more
~200
Heavy launches for one 2 GW plant
20,000 t at 10 kg/kW and 100 t a launch; 324 orbital attempts worldwide in 2025
~25–40 km²
Rectenna land for 2 GW of firm power
Against ~150–400 km² for ground solar with storage (Setcoin estimate)
03 · The cost
Power From Orbit Against Power on Earth
Setcoin's cost model with 30-year life, 8% cost of capital, 95% capacity factor and $0.3/W rectenna, against the top of Lazard's 2025 unsubsidised ranges and NASA's 2024 estimates.
Cost of electricity, $/MWh: space solar competes only if launch and hardware fall together
$ per MWh
Setcoin model (study ch. 28 and Appendix C); Lazard LCOE+ 2025; NASA OTPS 2024.
Try the model
What would power from orbit cost?
Start from Setcoin's reference plant: 10 kg in orbit per kilowatt delivered, $1,000 per kilogram to low orbit, a 2.5× factor to reach geostationary orbit and $2 per watt of hardware. Cut the launch price, halve the mass or put today's space hardware prices in, and compare the result with gas, nuclear and NASA's estimates.
Interactive model
Cost of electricity: what would power from orbit cost?
What does electricity from a space solar plant cost per MWh once you set mass, launch price, hardware and finance your way?
Scenarios
$357/MWhCost of electricity
$27.3/WCapital per watt
91.6%Launch share of capital
$54.60BCapital for a 2 GW plant
Gas combined cycle, top of range Earth benchmark
Firmed renewables, up to Earth benchmark
New nuclear, top of range Earth benchmark
Your plant
NASA OTPS 2024, lower estimate NASA estimate
NASA OTPS 2024, higher estimate NASA estimate
$ per MWh: your plant against firm power on Earth and NASA estimates
Show the calculation table
| Item | Value |
|---|---|
| Launch and transfer ($/W) | 25 |
| Space hardware ($/W) | 2 |
| Rectenna and ground ($/W) | 0.3 |
| Capital ($/W) | 27.3 |
| Capital recovery factor | 0.089 |
| Annual MWh per kW | 8.32 |
| Cost of electricity ($/MWh) | 357 |
Sensitivity: which input moves the answer most
What moves “Cost of electricity” most: each input 20% lower (left of a pair) and 20% higher
Capacity factor
Mass in orbit per kW delivered
Launch price to low orbit
Transfer factor to final orbit
Cost of capital
Plant life
Operations and servicing
Space hardware
Rectenna and ground systems
This is one of 5 interactive models in the report. The first 3 chapters of the report are open to everyone; a Space subscription, with a 7-day free trial, opens every model and its Excel file.
04 · Three findings
What Decides the Outcome
Setcoin's reading of the agency studies, demonstrations and cost model; arithmetic as labelled in the study.
92% of capital
Launch first
At $1,000/kg, launch and orbit transfer are almost all of the capital. Halving launch price, mass per kilowatt or the transfer factor each cuts the cost of power by 46%.
~100× gap
Then hardware
Qualified space arrays cost about €200–350 per watt; plants need about $2. Once launch falls below about $200/kg, hardware decides the cost.
km-scale, untested
Assembly at scale
The largest structure ever assembled in orbit is about 109 m across. A plant is kilometres across and must be assembled by robots, about 7 tonnes a day.
Try the model
How cheap must rockets get?
Pick a target cost of power and see the launch price a plant would need. At $2 per watt of hardware and 10 kg/kW, matching new nuclear at $141/MWh needs about $339/kg; matching gas at $70/MWh about $122/kg. Halve the mass or the hardware cost and the bar moves.
Interactive model
Break-even launch price: how cheap must rockets get?
For a target cost of electricity, what launch price to low orbit would a space solar plant need?
Scenarios
$214/kgLaunch price needed
12.6× lowerAgainst Falcon 9 list (~$2,700/kg)
4.2× lowerAgainst Starship reported (~$900/kg)
$7.65/WCapital allowed per watt
Hardware $1/WHardware $2/WHardware $4/W$/kg to low orbit needed (x: target $/MWh) · hover for values
Show the calculation table
| Target ($/MWh) | Launch needed at $1/W ($/kg) | Launch needed at $2/W ($/kg) | Launch needed at $4/W ($/kg) |
|---|---|---|---|
| 50 | 101 | 61 | 0 |
| 70 | 162 | 122 | 42 |
| 100 | 254 | 214 | 134 |
| 141 | 379 | 339 | 259 |
| 164 | 450 | 410 | 330 |
| 200 | 560 | 520 | 440 |
| 250 | 713 | 673 | 593 |
| 300 | 866 | 826 | 746 |
| 400 | 1,172 | 1,132 | 1,052 |
Sensitivity: which input moves the answer most
What moves “Launch price needed” most: each input 20% lower (left of a pair) and 20% higher
Target cost of electricity
Capacity factor
Mass in orbit per kW delivered
Transfer factor to final orbit
Cost of capital
Space hardware
Plant life
Operations and servicing
Rectenna and ground systems
This is one of 5 interactive models in the report. The first 3 chapters of the report are open to everyone; a Space subscription, with a 7-day free trial, opens every model and its Excel file.
05 · Geography
Who Researches, Tests and Buys
Government and university programmes, landmark beaming tests and the first commercial offtakers. Ringed: the only programme to have beamed power in orbit by October 2026. Switch between world, North America, Europe and Asia.
Power beamed in orbit (to date) · hover or tap a site for detail
All 15 sites, by category
Government and university programmes
- Caltech Space Solar Power Project (Pasadena) ◎ — MAPLE beamed power in orbit (2023)
- AFRL (Kirtland, New Mexico) — SSPIDR and Arachne
- NASA OTPS (Washington, DC) — 2024 cost study: $610 and $1,590/MWh
- Naval Research Laboratory (Washington, DC) — PRAM module flown on X-37B (2020)
- ESA ESTEC (Noordwijk) — SOLARIS preparatory programme
- Queen Mary University of London — UK space solar grant (~£960,600)
- University of Bristol — UK space solar grant (~£353,400)
- JAXA (Tsukuba) — Decades of research; OHISAMA
- Xidian University (Xi'an) — Ground beaming tests; national roadmap
Landmark beaming tests
- Goldstone (California) — 34 kW beamed over 1.6 km (1975)
- White Sands (New Mexico) — DARPA POWER: 800 W over 8.6 km (2025)
- Hawaii — Long-distance microwave test (2008)
- Munich — Microwave beam lights a model city (2022)
First offtakers
- Meta (Menlo Park) — Up to 1 GW reserved from Overview Energy (Apr 2026)
- Reykjavik — Letter of intent with Space Solar: 30 MW, 2030 target
Agencies, universities, companies and reporting; examples, not a complete list.
Try the model
How large is the spot on the ground?
A 1 km transmitter at 5.8 GHz in geostationary orbit spreads 2 GW over a spot about 4.5 km across, an average of about 125 W/m², an eighth of peak sunlight. Switch to 2.45 GHz, move to low orbit or try a laser and watch spot and intensity change.
Interactive model
Beam size: how large is the spot on the ground?
How wide is the beam where it lands, and how intense is it, for your choice of wavelength, transmitter and orbit?
Scenarios
4.5 kmSpot diameter
16.0 km²Spot area
125 W/m²Average intensity
0.12×Against peak sunlight
Public exposure guidance
Your beam, average
1979 design peak
Peak sunlight
W per m² (log scale): average beam intensity against reference levels
Show the calculation table
| Item | Value |
|---|---|
| Wavelength (m) | 0.052 |
| Transmitter diameter (m) | 1,000 |
| Distance (km) | 35,786 |
| Spot diameter (m) | 4,514 |
| Spot area (km²) | 16.006 |
| Average intensity (W/m²) | 125 |
Sensitivity: which input moves the answer most
What moves “Spot diameter” most: each input 20% lower (left of a pair) and 20% higher
Transmitter diameter
Distance to the ground
This is one of 5 interactive models in the report. The first 3 chapters of the report are open to everyone; a Space subscription, with a 7-day free trial, opens every model and its Excel file.
06 · Signals to watch
The Next Three Years
- 2026–2027First orbit-to-ground resultsCowboy Space's Reason-1 (launched October 2026), Japan's OHISAMA and AFRL's Arachne: measured power and efficiency at the ground.
- 2026–2027Starship prices for customersA published price per kilogram below a few hundred dollars would move the largest cost.
- 2027ESA decision after SOLARISWhether Europe funds a development phase toward an orbital demonstrator.
- 2028Company demonstrationsOverview Energy and Space Solar target orbital demonstrations; Meta's 1 GW reservation depends on them.
07 · Check it yourself
Test This Study Against the Live Record
Every figure in this study comes from the public record. These Setcoin services let you check the companies, contracts and counterparties behind it yourself.
Setcoin Sectors
Who is being paid to build
Cited R&D awards and prime contracts in space and aerospace, by organisation and readiness gate, from public procurement and grant records.
Open the space sector record →Setcoin for Venture
Check a company's claims
A company's round, filings and statements checked against the public record, to the same standard as this study.
Check a company →Time-to-Power
How long sites wait for power
How long data-centre and industrial sites wait for grid connections today, the firm-power problem space solar claims to solve.
Open Time-to-Power →08 · The full study
What's Inside
Physics and programmes
- Sunlight in orbit, beam physics, efficiency chains and beam control
- Microwaves, lasers, mirrors, rectennas, weather, spectrum and safety
- ESA SOLARIS, the UK, NASA, Caltech, AFRL, DARPA, Japan, China and others
- Companies, the Meta–Overview agreement and the demonstrations so far
Engineering and economics
- Mass, solar cells, launch, assembly, thermal control, orbits and operations
- Setcoin's cost model, sensitivities, break-even map and the first plant
- Firm power on Earth, ground solar with storage, the value of firmness
- Financing, insurance, public money, learning curves and three illustrative plants
Markets, rules and outlook
- Defence, data centres, islands, mines, satellites, the Moon and hydrogen
- Regulation, international law, health evidence, environment and public acceptance
- Scenarios to 2050, roadmap, stage gates and what would have to be true
- Checklist, risk register, signals, misconceptions and twenty questions answered
Economics
Cost of electricity
Mass per kilowatt, launch price, orbit transfer, hardware, rectenna, capacity factor, life and cost of capital turned into dollars per MWh, against gas, nuclear, firmed renewables and NASA's estimates.
Thresholds
Break-even launch price
For any target cost of power, the launch price to low orbit a plant would need, at three hardware costs.
Physics
Beam size and intensity
Diffraction sets the spot: choose a frequency or laser, transmitter size and orbit to see spot diameter and intensity against sunlight and exposure guidance.
Free data tools
Check the live record yourself
The study's findings move with launches, contracts and filings. These free Setcoin tools show the current public record behind them, refreshed from the catalogues and procurement registers.
Free tool
Space Contracts & Tender Radar
607 new US federal space awards and European tenders from the last twelve months, by part or service bought, buyer, country and stage, with the tenders still open.
See public demand for space power: solar arrays, batteries and power R&D, awarded and open.
Open the radar →Free tool
Space Claim Check
Type an operator’s name and see what the public satellite catalogues record: satellites launched, in orbit, operating and re-entered. The full check adds US contracts, SBIR awards, UK and NOAA licences and list screening.
Check what the catalogues record for a company’s demonstration missions.
Check an operator →Questions
Questions About the Study, Answered
What is space-based solar power?
Collecting sunlight in orbit, where a collector in geostationary orbit is lit about 99% of the year, and sending the energy to Earth as a microwave or laser beam, or as reflected sunlight. A receiving antenna on the ground, a rectenna, converts microwaves back into electricity for the grid.
Has power been beamed from space to Earth?
At very small scale. Caltech's MAPLE experiment transmitted power wirelessly in orbit in 2023 and detected a signal at a receiver on Earth. On the ground, NASA beamed 34 kW over 1.6 km at Goldstone in 1975, and DARPA sent more than 800 W by laser over 8.6 km in 2025. No system has yet delivered useful power from orbit to the ground.
How much would electricity from space cost?
On Setcoin's reference case, 10 kg in orbit per kilowatt, $1,000 per kilogram to low orbit and $2 per watt of hardware, about $357 per MWh, with launch 92% of capital. At $200 per kilogram it falls to about $95 per MWh, and with half the mass and $1-per-watt hardware to about $50. NASA's 2024 study estimated $610 and $1,590 per MWh for its reference designs.
Is the microwave beam dangerous?
Designs keep intensity low: a 2 GW beam over a 4.5 km spot averages about 125 W/m², with a design peak of about 230 W/m² at the centre, below peak sunlight, falling to public exposure guidance of about 10 W/m² at the edge. Beams are steered by a pilot signal from the ground and spread out harmlessly if it stops. Lasers need stricter controls because they can harm eyes.
Why are the antennas so large?
Diffraction. The spot size is about 2.44 × wavelength × distance ÷ transmitter diameter. From geostationary orbit, a 1 km transmitter at 5.8 GHz makes a spot about 4.5 km across; at 2.45 GHz about 10.7 km. Lasers make spots under 100 m but are blocked by clouds.
How many launches would a space solar plant need?
At 10 kg per kilowatt delivered, a 2 GW plant weighs about 20,000 tonnes, which is about 200 launches of 100 tonnes each. That compares with 324 orbital launch attempts worldwide in 2025. At 25 launches a year the campaign would take about eight years.
Who is developing space-based solar power?
Agencies and universities including ESA (SOLARIS), NASA, Caltech, the US Air Force Research Laboratory, DARPA, JAXA and Chinese institutions such as Xidian University, and companies including Cowboy Space (formerly Aetherflux), Overview Energy, Space Solar, Star Catcher and Reflect Orbital. Setcoin analyses public markets and programmes for information only and does not recommend any security.
What is the Meta and Overview Energy agreement?
In April 2026 Meta agreed with Overview Energy for early access to up to 1 GW from Overview's planned geostationary system, which would beam near-infrared light to existing solar farms so they can produce at night. Financial terms were not disclosed; Overview targets an orbital demonstration in 2028. It is a reservation, not a purchase of delivered power.
When could space solar power supply the grid?
Setcoin's roadmap places orbital demonstrations delivering 100 W to 1 kW in 2026–2028, megawatt demonstrators in the 2030s, a grid-connected demonstration plant of tens to hundreds of megawatts in 2034–2040 and gigawatt commercial plants in the 2040s, provided launch, mass and hardware cost all fall.
How do I read the full study?
The first three chapters are open to everyone in full, with no account; the rest can be previewed. A space sector subscription, with a free trial, opens all 98 chapters and 3 appendices, the five interactive models and their Excel files.
Setcoin Research analyses public markets, filings and programmes for information only. It is not investment advice and does not recommend any security.
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