Cleantech’s European calendar splits between the mass-audience summits – ChangeNOW in Paris is the largest climate event on the continent by attendance – and the smaller investor-focused gatherings where the deals actually happen. Ranked by verified attendance where the organiser publishes it.
1Rank
Carbon accounting, climate risk analytics, recycling tech 26-28 Apr 2027, Grand Palais, Paris 40,000 attendees
The largest climate and impact summit in Europe, filling the Grand Palais for three days with founders, corporates, policymakers and investors across every cleantech sub-theme. Runs a large startup exhibition zone and structured investor meetings.
Why it is hereThe biggest climate-tech audience anywhere in Europe – if you need reach across every sub-theme at once, nothing else comes close.
2Rank
Carbon accounting, direct air capture, ESG reporting 27-28 Apr 2027, Olympia, London 7,500 attendees
London's net-zero congress at Olympia, with strong carbon removal and CCUS programming alongside corporate decarbonisation. Runs the same week as ChangeNOW, which splits the April climate calendar between Paris and London.
Why it is hereThe deepest carbon removal and direct air capture audience in Europe – the specialist room for CCUS founders.
3Rank
Climate risk analytics, EV makers Messe Berlin (2027 dates to be confirmed) 7,000 attendees
Berlin's green technology festival, co-founded by Nico Rosberg, mixing a consumer-facing exhibition with a conference programme. Strong EV and mobility crossover reflecting Berlin's automotive ecosystem.
Why it is hereThe German cleantech audience with an EV and consumer tilt – the right room if your product is visible rather than infrastructural.
4Rank
Climate risk analytics, climate policy 8 Jun 2027, Hofburg Vienna 1,000 attendees
The Schwarzenegger Climate Initiative's annual summit at the Hofburg, bringing heads of state, corporate leaders and climate founders together for a single high-profile day.
Why it is hereSmall but exceptionally senior – the one European climate room where government leaders outnumber founders.
5Rank
Climate risk analytics, Nordic cleantech 28 May 2026, Kista Science Tower, Stockholm 300 attendees
Techarena Group's climate-focused day in Stockholm, spun out of the broader Techarena conference to give Nordic cleantech its own stage.
Why it is hereThe entry point to the Nordic cleantech ecosystem, which leads Europe on grid, heat pumps and battery recycling.
6Rank
Climate risk analytics, ESG reporting, impact investing 27-29 May 2026, Tolhuistuin and Ruigoord, Amsterdam Attendance not published
The Katapult Foundation's impact investing festival, with a dedicated investor day at Tolhuistuin before the broader festival programme at Ruigoord. Impact fund managers and LPs rather than corporates.
Why it is hereThe one cleantech event built around impact investors rather than exhibitors – go here to meet the LPs behind the climate funds.
Attendance figures come from each event’s own record and organiser statements. Where an organiser does not publish a figure, the entry says so rather than estimating. Note that ChangeNOW and Innovation Zero overlap in late April 2027 – founders exhibiting at both need to plan for a Paris-London split.
Common questions
Which is the largest cleantech event in Europe?
ChangeNOW Summit in Paris at 40,000 attendees, held at the Grand Palais each April. It is the largest climate event on the continent by a wide margin.
Which cleantech event is best for carbon removal founders?
Innovation Zero World Congress in London, which has the deepest direct air capture and CCUS programming of any European event.
Do ChangeNOW and Innovation Zero clash?
Yes – both run in the last week of April 2027, ChangeNOW 26-28 April in Paris and Innovation Zero 27-28 April in London. Plan for one or a split team.
Does Sesamers take payment for placement on this list?
No. Rankings are by verified attendance. Events are listed because they are tracked in the Sesamers database, not because they paid.