The world's largest and longest-running cleantech accelerator, supporting 100–150 US cleantech startups annually with a five-month program of mentoring…
Cleantech Open is the world's largest cleantech accelerator, celebrating its 20th anniversary in 2025 with a five-month program for 100–150 US-based cleantech startups per year. The program includes customer discovery, mentoring from 1,000+ experienced mentors, investor meetings, and startup-corporate matching, culminating in regional showcases and the national Global Forum. Alumni from 4,000+ entrepreneurs have collectively raised over $4 billion in funding. The 2026 program runs May through October, with a Global Forum in Boston. Program duration: 5 months.