In 2021, Bangladesh reached 97% nation-wide electricity access. With over 4.1 million solar home systems (SHS) installed by 60 Partner Organisations (POs) providing renewable electricity to more than 22 million rural people, SHS and microfinance have been instrumental in bridging and achieving the country's universal access goal. However, a huge gap remains in achieving the country's 100% use of renewable energy by 2050, with only 3.1% of current electricity generation accounted for by renewables. While at centralised level, governmental institutions are struggling to move past the legacy mandate of grid extension to an energy transformation paradigm at decentralised levels, rural Bangladeshi villages are already leading this transformation. Today, 100 solar peer-to-peer microgrids, built following the swarm electrification pathway, allow end-users to run appliances, charge vehicles, and to trade renewable electricity for income. In this paper, we describe the organisational model of the partnership between Grameen Shakti, Bangladesh's largest PO, and climate-tech start-up ME SOLshare, the swarm electrification implementer. We assess, using data from the peer-to-peer grids, their socio-economic and environmental impact, and their contribution to the SDG 2030 Agenda. Finally, we give an outlook towards the potential of achieving sustainable energy development through a scale-up of the swarm electrification approach, including under a scenario of 100% national grid electrification.