Answer: About 350 earth masses.
Question: After thinking about it, living on a black hole is clearly impractical, but what if I want to replace my heating system with one? What size black hole will produce a comfortable temperature of 70 F?
Answer: Roughly the mass of Ceres.
Question: I want to go see what an event horizon looks like up close, so what size black hole is needed for the gravity to be 1G at its "surface" for optimal sightseeing?
Answer: About a trillion solar masses. It might be a little tricky finding or making one that large, as the largest known in galaxy centers are on the order of 10^10, not 10^12.
This doesn't make any sense to me. By definition at the event horizon gravity is enough to keep light from escaping. Light can easily escape from 1G.
Without thinking too deeply, I suspect the issue is that you could never be stopped at that location in the first place, unlike Earth's surface.
But the event horizon of such a black hole would be far larger than that of the Earth. Move 6400 km away, and you'll still have a gravity of ~1G.
Rinse and repeat, and you'll find that even light won't be able to escape.
That's a hell of a lot of energy. (If I'm doing the math right, the potential energy difference is on the order of ~20% of the rest mass at the event horizon)
Answer: The appropriate mass is roughly the size of a WWII destroyer, or somewhat more than the largest dump truck in the world. There might be a drawback in that the energy release will be about 50,000 megatons per second. That might affect how fast your egg cooks.
Since 50,000 megatons/sec is the starting value, and it'll get bigger as those three minutes count down.
I asked "so if I want to use a black hole to replace a 60 watt light bulb, how much mass do I need?" And the answer is, roughly that of Phobos. It would also last over 10^22 years, so it might even be cost effective!
If such a thing existed, there would likely be more than 1. How long would it take such an object to consume a star like our sun if it grazed or hit the star, vs a harmless hyperbolic flyby?
Using this calculator, we find that a black hole with the mass of 433 Eros, 6.687E15 kg, would be quite hot, some 18 million kelvin, but emitting just 8 watts of power, and be 0.009 nanometres in radius. Pretty hard to find.
Let's try something smaller. 162173 Ryugu, the rock that Hayabusa2 landed on, is only 4.5E11 kg. This gives you a much brighter hole: 1758 megawatts at 2.72657E11 kelvin.
Interestingly, this may make it harder to detect! Its blackbody emission peak is at 9,211 KeV, and the Chandra X-Ray observatory only goes up to 10 KeV. (Focusing very-high-energy photons is not easy) You'd have to detect it from the fraction of total power it emits lower down in the spectrum.
In actual fact, moving mount Everest To The Moon is trivial in comparison with the task of creating a black hole. It's a feat only accessible to Kardashev type 2, at the very least 1.5, civilisations. We are talking about civilisations that can move small planets at will.
The most credible approach is to build giant gamma-ray lasers, and focus so much energy into a spot to small, that the weight of light itself will collapse the spot into a tiny black hole made of pure energy, Kugelblitz.
Once you would have a black hole formed that way, you could continue force-feeding it with lasers or particle beams to weigh whatever amount you desire. It would be a very energy-inefficient process.
At some point the black hole reaches a mass where it's Eddington limit allows it to feed by 'normal' means faster than it evaporates by hawking radiation. At that point it could server to convert matter to energy.
... Ignoring the HUGE gap between smashing together a few atoms so a small fraction of their bits evaporate and smashing them so hard they pretty much disappear.
Working backwards, 1 megaton per second (4x10^9 megawatts) gives us a black hole of 3x10^8 kg.
0: http://xaonon.dyndns.org/hawking/