There's not really any meaningful extra size for Timescale compared to standard Postgres.

I mean, there's a little extra information about each chunk (table name, its constraints, triggers, etc), and we cache this information in memory to speed up the query/insert side of things. But it's pretty common for these chunks to be on the order of 100s MB to GB, so this is just noise compared to the underlying data/indexing size.

So on the real storage size, the only potential difference is index size: say 50 indexes over 2GB data each vs 1 index over 100GB data? Haven't really looked into this for all different index types, but seems rather modest. Can try to dig up some more data.