When we think about solar energy, chances are we picture gleaming photovoltaic panels—on rooftops or sprawling across sunny fields—turning sunlight into electricity. What rarely comes to mind is another form of solar power: heat. Direct, immediate, practical. And in many ways, overlooked.
Solar thermal energy uses the sun’s radiation to heat water or other fluids directly. It’s a simple technology—highly efficient, low-maintenance, and incredibly versatile. From homes and hospitals to hotels, swimming pools, and even industrial processes like pasteurization, solar thermal power quietly powers hot water systems and heating networks across the world.
“People still think of solar thermal as something small, for individual homes,” says Marisol Oropeza, a solar thermal advocate and industry leader based in Germany. “They don’t see how companies are using it to decarbonize entire operations.”
That perception is a problem—not just for the technology, but for the climate. Heat accounts for nearly half of the world’s final energy consumption and is responsible for 38% of energy-related CO₂ emissions, according to the International Energy Agency. And yet, solar thermal still operates in the shadows of its more famous cousin, solar PV.
Small Growth, Big Potential
As of 2023, global solar thermal capacity reached 560 GWth—up just 3% from the year before. For context, solar PV power generation jumped by a record 25% over the same period.
Still, that modest solar thermal growth saved an estimated 49.1 million tons of oil and avoided 158.4 million tons of CO₂—roughly the annual emissions of 36 million gas-powered cars.
It’s that untapped potential that drives Oropeza. She launched the Heat Changers campaign in 2018 to elevate solar thermal from niche to mainstream, securing the recognition that the technology needs to reach full potential. “We’re telling a new story about solar energy,” she says. “One that shows how solar heating can transform homes, businesses, and entire cities.”
From producers of food to pharmaceuticals, construction and sustainable raw material, many businesses have already benefited from using the technology. ISA TanTec, which processes eco-friendly leathers and sustainable new materials for footwear, handbag, apparel and accessories, say that the technology has helped them cut costs and enhance competitiveness.
“Solar heat helps us reduce energy costs significantly and more important it keeps them predictable and stable. In fact, it makes us more competitive and attractive on the market as our customers are looking for more eco-friendly suppliers,” said Tom Schneider, ISA TanTec co-founder.
Lavin, a Mexican company producing products for personal hygiene say that Solar Thermal helped them enhance efficiency in their production processes by 40%. “We are a socially responsible company motivated by caring for the environment. We have managed to integrate a water preheating solar system into our emulsion production processes for body creams and deodorants, increasing the efficiency of our production process by 40% by reducing production time in our core process,” said Luis Martinez Lavin, Chief Operating Officer, Industrias Lavín de México.
From Mexico to Germany: A Chance Encounter with the Sun
Oropeza’s path into the solar thermal sector wasn’t planned. After studying business administration in Mexico and working in government, she moved to Germany for a master’s degree in European studies. A job opportunity introduced her to the solar thermal industry—and something clicked.
It wasn’t just the technology that won her over, it was the passion and the enthusiasm of the people working in the sector.
Heat Changers: Turning Up the Volume
Heat Changers emerged as a response to a clear problem: solar thermal is not sufficiently visible. The campaign gathers a global network of professionals, advocates, and users working to showcase the diversity, benefits, and scalability of solar heat.
“It’s about saying, ‘You can make the change now,’” says Oropeza. “You can stop using gas and start using solar thermal. It’s cheaper, simpler, and you gain energy independence—while cutting emissions.”
Public policy, she says, is the real accelerator. In her home country, Mexico, while the market is growing, solar thermal deployment could be much higher if there were more incentives for all sectors beyond and not only residential. Marisol underlined that a specific incentive programme for the industrial sector to use solar thermal is needed.
By the end of 2023, Mexico’s installed solar thermal capacity hit 4.5 GWth, making it the second-largest market in Latin America after Brazil—and the sixth fastest-growing globally, according to the Solar Heat Worldwide Report.
From 2022 to 2023, Mexico’s market grew 5%, outpacing the global average and Brazil’s national average. Most of that heat is used in homes (58%), pools (28%), and to a lesser extent, industry (6.5%). Yet Mexico remains an outlier. In places like Cyprus, Turkey, and Caribbean islands, solar water heaters are everywhere. In most of the world, however—even sun-drenched “Sunbelt” nations—solar thermal is still under the radar.
A Practical, Affordable Solution Hiding in Plain Sight
Why the lack of buzz? Unlike PV, solar thermal lacks the sleek aesthetic and big energy headlines. But when it comes to heating water, it’s a powerhouse. A typical photovoltaic panel captures about 20% of solar radiation. A solar thermal collector? Up to 80%. That means better performance using less space.
Solar thermal systems are also affordable and accessible: they’re often locally made, have lower upfront costs than PV, require minimal maintenance, and last up to 25 years. In sunny countries, payback times can be as quick as two to five years.
There’s an environmental bonus, too: “You’re not contributing to the waste problem,” Oropeza says. “And you’re not dependent on rare, imported materials.”
REbooting the World, One Shower at a Time
“Taking hot showers with electricity is a waste of energy,” Oropeza says. “You’re ignoring the sun that’s right above your head.” She calls for “rebooting” the way we heat water and spaces in homes, commercial and industrial sites. The REboot the World campaign pushes solar thermal into the spotlight—where it can finally claim its role in helping cities and citizens become more resilient, sustainable, and energy independent.
“Solar thermal is a big part of the solution,” she says. “It’s time we treat it that way.” Learn more about the Heat Changers campaign and, like Marisol Oropeza did, let us know your REbootTheWorld with Renewables story.
