From the PDF:

> On its own, a PBH of mass 5M⊕ has a Hawking temperature of 0.004 K, making it colder than the CMB, and since it’s radius is rBH ∼ 5 cm, the power radiated by the PBH alone is minuscule.

Also wolfram alpha says it would take 7e52 years to evaporate from hawking radiation, so it's quite stable: https://www.wolframalpha.com/input/?i=%285120*pi*G%5E2*%285+...

My understanding is that a black hole large enough to be colder than the CMB will grow (gain more mass energy by absorbing CMB photons, even in "empty" space, than it loses by Hawking radiation), continuing to cool.

I assume but am not sure that the cooling of an already-sufficiently-cold black hole in this manner is slower than the cooling of the CMB itself due to expansion, so that at some point as the universe winds down it will begin to shrink again and eventually evaporate, but definitely over the lifetime of any star we see a black hole this side won't radiate significantly, or evaporate.

I did the figures a while back on what it would take to build a Hawking-radiation-basedv mass-to-energy power plant (in orbit, obviously), and I was astounded at how tiny the black holes have to be in order to get appreciable power output from them.