Let's say, (in the far future), that humans have become really advanced beings and are at the verge of becoming a Type III civilisation. Now, they need a gargantuan energy source for various purposes, for e.g. making megastructures, weapons and for powering a energy-hungry civilisation. So most of the humans come up with a plan- Turn the Milky Way into a quasar.
The idea here is really simple. Black holes are really sloppy eaters. Only a fraction of the mass that comes near them is absorbed, while the rest is blasted away at nearly the speed of light, in the form of jets, radiation or light.
So, the civilisation here, comes up with this plan:
Various planets and stars are nudged into the proximity of Sagittarius A*, the Milky Way's supermassive black hole. These planets and stars are broken up by the powerful tidal forces, and form a dense accretion disk around the black hole. The black hole then blasts this matter out into space, creating powerful jets.
Now here comes the cheat-code (or trick). Paper-thin mirrors are installed near the black hole, at a sufficient distance from the event horizon. These mirrors reflect the jets and radiation of the black hole, and aim it towards a set of orbiting solar panels (black hole panels?). These panels absorb the radiation and the jets' energy, and the energy is used either directly, or stored in giant batteries, which I shall discuss in a future question. The mirrors themselves are kept in place by a delicate balance of radiation pressure from the jets, and the powerful gravity of the SMBH.
The mass being consumed in question is about 5-10 solar masses per month.
Diagram of the setup below: The question here is:
How much energy would a civilisation get from a quasar Milky Way per day, in terms of wattage?
(Note: This question does not ask for the energy harvested from Hawking Radiation or anything similar)