Solar energy, once a costly and niche technology, has become one of the most affordable and widely used power sources in the world. A new study from the Massachusetts Institute of Technology (MIT), published in PLOS ONE, has traced the dramatic fall in solar costs — more than 99 percent since the 1970s — to a complex web of innovations that span far beyond solar technology itself.

Researchers identified 81 distinct breakthroughs that have steadily lowered the cost of photovoltaic (PV) systems over the past five decades. These include technical improvements within the panels, such as wire-sawing methods that reduce silicon waste, alongside systemic changes like faster permitting procedures for new projects. Strikingly, many of these advances emerged from industries unrelated to solar power, including semiconductors, glassmaking, and even legal reforms.

“The story of how solar became the cheapest form of electricity in history is one of steady, systemic innovations,” said Kostantsa Rangelova, global electricity analyst at energy think tank Ember. She explained that incremental advances became transformative when combined with economies of scale and mass production, magnifying small efficiencies into significant cost reductions.

The effects of these changes are already reshaping energy markets. In June, solar power generated more electricity than any other source in the European Union for the first time — a symbolic milestone amid surging clean energy investments. Globally, around €1.7 trillion was invested in renewables last year, outpacing fossil fuels by €685 billion. Offshore wind has also become more cost-effective, but the price drop in solar remains the most dramatic, positioning it as a leader in the global shift to renewables.

Looking ahead, MIT researchers argue that the next phase of cost reductions may come from unexpected areas, including software, robotics, and grid integration. Tools such as automated engineering reviews, AI-driven design, and modular panel construction could deliver new savings and improve quality. “What we’ve seen so far in PV may really just be the beginning,” said study co-author Magdalena Klemun, noting that spillovers from other sectors will continue to accelerate change.

However, challenges remain, particularly in end-of-life management. Solar panels, designed to last over 30 years, are difficult to dismantle and recycle, raising concerns about mounting waste as older units retire. Researchers and companies across Europe, Australia, and beyond are now exploring sustainable recycling methods, repair programs, and reusable designs to address this issue. Similar concerns are emerging in the wind industry, where turbine waste could reach 43 million tonnes by 2050.

The MIT team emphasized that many of the systemic innovations driving solar’s success originated not only from laboratories and corporations but also from government-led initiatives. By learning from solar’s history, policymakers and industry leaders can better support breakthroughs in other renewable technologies.

“Through this retrospective analysis, you learn something valuable for future strategy,” said Jessika Trancik, lead author of the study. “It is also useful to know what adjacent sectors may help support improvement in a particular technology.”

With solar now at the forefront of clean energy, its past offers critical lessons for accelerating the world’s transition toward a net-zero future.