It’s impossible to say, but if we assume it’s a typical Li-ion battery supplying 3.7V, then:
9 kAh x 3.7 V = 33.3 kWh
So, it would be enough to power the average American house (10 MWh/year) for 1.2 days, or 4 days for a typical European flat (3 MWh/year).
Edited wrong yearly consumption
Seems like you answered your own question. If a gaming software engineering privacy enthusiast isn’t a power user, I don’t know what is.
Also, Tumblweed really isn’t intimidating. Give it a try.