September 5, 2023

Cooling so hot right now: French startup raises €10m for greener aircons

The French startup has raised a second round to increase the production of its air conditioners that rely on natural water and air phenomena

French climate startup Caeli Energie has raised €10m in equity and debt — its second funding round — to increase the production of its low-carbon air conditioners. The round was led jointly by Asterion Ventures, Starquest Capital, Bpifrance and Rise PropTech and follows a €2.1m pre-seed round raised at the start of 2022.  

The startup has developed a patented technology that it says is five times more energy-efficient than the highest performing air conditioners currently on the market. 

Air conditioning couldn’t get more topical, with countries around the world struggling to cope with increasingly frequent heat waves. But traditional air conditioners are notoriously bad for the environment — cooling technologies are estimated to contribute around 7% of global emissions.


“There is a possibility of real demand from people who are very hot in the summer but don’t want to buy an air conditioner for environmental reasons,” says Rémi Perony, the cofounder of Caeli Energie.

The problem with aircon 

Air conditioners are extremely energy-hungry, rely on polluting refrigerating gases and work by expelling warm air outside of our homes, making cities even hotter. 

Caeli Energie cofounders Perony and Stéphane Lips are taking a different approach. They’ve built an air conditioner based on a heat exchanger that produces cold air by evaporating water. 

Perony was inspired by rudimentary cooling systems that he saw when he was living in New Delhi, which were similar to other centuries-old cooling architectures like wind-catchers that can be found in Iran. These systems rely on catching warm air and blowing it over water to naturally cool down a room.

“When you come out of a swimming pool, you get colder,” says Perony. “That’s because the water on the surface of your skin evaporates. We are only optimising this natural phenomenon.”

Caeli Energie’s technology requires significant volumes of water — around 20 litres per day for an average user — but consumes much less energy than a traditional air conditioner and doesn’t use refrigerants. Perony says the device requires a similar amount of power to a WiFi box. 

Serving public bodies

When Caeli Energie launched in 2020, it planned to sell its technology to consumers. But the company is now focusing on equipping buildings in the public sector — like town halls, hospitals, care homes and kindergartens — where it has found significant demand.

The startup has deployed 50 units to date, as part of partnerships with French customers ranging from public housing providers — like Valence Romans Habitat and Alpes Isère Habitat — to the French Interior Ministry.

Industrial companies have also shown interest, says Perony — but Caeli Energie isn’t ready to take on that market yet. 

“What’s at stake for us is to not get the scaling process wrong,” says Perony. “I’ve seen many hardware startups burning their wings because they tried to grow too fast.”


With its latest funding round, Caeli Energie is aiming to test and improve the strength of its production process. It also plans to increase capacity by automating parts of its production line, which will increase production capacity 50-fold.

“We are going from a post-lab startup to a small company,” says Perony.

Caeli Energie also plans to double its team of 19 by recruiting more than a dozen new employees in the next 18 months, mostly in sales and marketing roles, to expand the company’s development in France and then across Europe.

Made in France

The startup prides itself on giving consumers a “made in France” alternative to air conditioners — with a system entirely built on the company’s site in Grenoble — while remaining cost-competitive. The company is selling its product and installation to its current customers in the public sector for about €3,000, a similar price to traditional air conditioners, with additional cost savings on energy bills.

“We have managed to substitute something that is highly pollutant and usually imported from the other end of the world with a locally-produced, low-carbon system, while remaining cost-competitive,” says Perony. An encouraging signal for Europe’s climate tech scene.

Daphné Leprince-Ringuet

Daphné Leprince-Ringuet is a reporter for Sifted based in Paris and covering French tech. You can find her on X and LinkedIn