They have a couple of good pages where they define solarpunk, I’ll share a few quotes below too.
wiki.slrpnk.net/articles:whatissolarpunk
wiki.slrpnk.net/articles:manifesto

Solarpunk is a rebellion against the structural pessimism in our late visions of how the future will be.
Not to say it replaces pessimism with Pollyanna-ish optimism, but with a cautious hopefulness and a daring to tease out the positive potentials in bad situations.
Hope that perhaps the grounds of an apocalypse (revelation) might also contain the seeds of something better; something more ecological, liberatory, egalitarian, and vibrant than what came before, if we work hard at cultivating those seeds.

Solarpunk is a movement in speculative fiction, art, fashion, and activism that seeks to answer and embody the question “what does a sustainable civilization look like, and how can we get there?” […]

1. We are solarpunks because optimism has been taken away from us and we are trying to take it back.
   2. We are solarpunks because the only other options are denial or despair.
   3. At its core, Solarpunk is a vision of a future that embodies the best of what humanity can achieve: a post-scarcity, post-hierarchy, post-capitalistic world where humanity sees itself as part of nature and clean energy replaces fossil fuels.
   4. The “punk” in Solarpunk is about rebellion, counterculture, post-capitalism, decolonialism and enthusiasm. It is about going in a different direction than the mainstream, which is increasingly going in a scary direction.