In 1975 a single watt of solar photovoltaic capacity cost about $106. Today it costs roughly ten cents. Nothing about physics changed — what changed was how many we built. The price of clean energy hardware has followed one of the most reliable patterns in industrial economics, and almost every official forecast has missed it.
Fall in solar module price, 1975 → 2024
99.9%
From $106.09 per watt in 1975 to about $0.10 per watt in 2024, in constant 2025 dollars. Over the same span, cumulative installed solar capacity rose from 0.3 megawatts to roughly 2,900 gigawatts — a factor of about ten million. Our World in Data (2025), from Nemet 2009, Farmer & Lafond 2016, IRENA 2025; Ember 2026
01 / The price of a watt
Three decades of falling, plotted on a scale that has to be logarithmic
A linear chart cannot hold this range: the 1975 price is a thousand times the 2024 price. Each equal step along the strip below is a tenfold cut.
Solar PV module price, constant 2025 US$ per watt — logarithmic scale
Prices deflated to constant 2025 US$. Sources: Nemet (2009) for 1975–2003; Farmer & Lafond (2016) for 2004–2009; IRENA Renewable Power Generation Costs in 2024 for 2010 onward, compiled by Our World in Data.
02 / Wright's law
Twenty percent off, every time the world doubles what it has built
Solar's fall is not a series of lucky breakthroughs. It tracks cumulative production: for more than four decades, each doubling of installed capacity has cut module prices by about 20% — a measured learning rate of 19.3%.
Illustrative arithmetic — price index after N doublings at a 20% learning rate
Illustrative, not measured: applying a flat 20% cut across ~23 doublings leaves 0.6% of the 1975 price — a 99.4% fall. The observed fall is 99.9%, slightly steeper than the rule predicts, because module prices dropped faster than trend after 2023 as Chinese manufacturing capacity outran demand. Learning rate of 19.3% per doubling: Our World in Data.
03 / The second curve
Batteries are now running the same play, one decade behind
Lithium-ion pack prices are 93% below their 2010 level. The only year they rose was 2022, when lithium and nickel spiked — and even that reversed within a year.
Lithium-ion battery pack price, global volume-weighted average, US$ per kWh
BloombergNEF annual Lithium-Ion Battery Price Survey, 2020–2025. Nominal US$, volume-weighted across EVs, buses and stationary storage. BNEF puts 2025 prices 93% below 2010, when packs cost above $1,200/kWh in real terms.
04 / The same cell, three prices
Where a battery is built now matters more than what is inside it
In 2025 the cheapest packs were not the most advanced ones. Chemistry and geography each opened a gap of roughly 50%.
Average lithium-ion pack price, 2025 — US$ per kWh
ChinaALL APPLICATIONS
$84
North America+44% VS CHINA
$121
Europe+56% VS CHINA
$131
LFP chemistryIRON-PHOSPHATE
$81
NMC chemistryNICKEL-MANGANESE-COBALT
$128
Stationary storage−45% IN ONE YEAR
$70
Electric vehiclesPACK AVERAGE
$99
BloombergNEF, December 2025. Grid batteries became the cheapest segment for the first time, undercutting EV packs — a 45% fall in a single year, driven by cell overcapacity and the shift to LFP.
05 / What the models missed
The most consistent error in energy forecasting is optimism about fossil fuels
An ex-post review of every World Energy Outlook from 1993 to 2022 found the same failure repeated: fossil and nuclear growth overstated, solar growth understated — sometimes by a decade or more.
Annual global solar capacity additions — forecast vs. delivered, gigawatts
IEA Net Zero scenarioPEAK RATE PROJECTED FOR 2040
657
Actually built in 2025REACHED 15 YEARS EARLY
647
Actually built in 2024PRIOR RECORD
582
China alone, 2025MORE THAN HALF THE WORLD
378
India, 2025UP FROM 32 GW IN 2024
49
The 2022 IEA Net Zero Emissions scenario has annual solar installation peaking at 657 GW in 2040. The world installed 647 GW in 2025. Separately, the 2010 World Energy Outlook projected 294 GW of cumulative solar capacity by 2030; that level was passed in 2016, and cumulative capacity ended 2025 near 2,900 GW. Sources: Lopez, Keiner & Breyer (2025); Ember (2026); IEA WEO 2010.
06 / The stakes
Cheap is now the argument, not the concession
For most of the last century, decarbonising was framed as paying a premium. On current costs, the premium runs the other way.
$12T
Modeled net savings
Estimated saving from a fast transition to a net-zero energy system by 2050, versus continuing current fossil use — before counting any climate damages. A modeled projection, not a measurement.
91%
Cheaper than fossil
Share of newly commissioned utility-scale renewable capacity in 2024 that produced power below the cost of the cheapest new fossil-fuel alternative.
814 GW
Added in 2025
Record solar-plus-wind capacity added worldwide in a single year, 17% above 2024. Nearly 4 GW of solar went in for every 1 GW of wind.
Cost declines, by measure
Solar module price1975 → 2024
−99.9%
Battery pack price2010 → 2025
−93%
Solar electricity, LCOE$0.417 → $0.043 / kWh
−90%
Utility solar, installed costTO $691 / kW IN 2024
−87%
Grid battery packs2024 → 2025 ALONE
−45%
Periods differ by series and are labelled on each bar. Sources: Our World in Data (2025); BloombergNEF (2025); IRENA, Renewable Power Generation Costs in 2024 (2025).
Why it matters
A learning curve is a policy instrument, not a weather report.
Prices fall because volume rises. Deployment is the mechanism — every gigawatt installed is a down payment on the next one being cheaper.
Cost curves are not promises. Wind LCOE ticked up 3% in 2024, and module prices rose 30–100% during the 2021–23 supply crunch before resuming their fall.
Treat long-range cost forecasts with suspicion in both directions. The models that missed solar had no bad data — they had a bad prior.
The remaining hard part is not generation. It is grids, permitting and storage duration — where $70/kWh packs have only just started to bite.