It's not about amperage...
Hammer drills are garbage. In a hammer drill, the whole chuck moves back and forth, and that imparts some motion the the drill bit. Most of the power is wasted moving the chuck (which is heavy) back and forth, and very little power ends up doing useful work.
So instead you get a rotary hammer with a SDS chuck. This has a pneumatic hammer hitting the back end of the drill bit, so it is like hitting a chisel with a hammer. Most of the energy goes into the useful job of drilling the hole. It's much faster.
How fast a rotary hammer will drill depends on the impact energy (in Joules) which is mentioned in the product description. 2 Joules is fine for light work (up to 15mm diameter) and also not expensive. For big holes like 20mm or more, get more joules, but the tool will be heavy and more expensive.
With 2-3J tool and a 3/8" (10mm) bit in concrete you can expect about 15-20 seconds for your 5 inch hole. Maybe 30 seconds if the drill is a bit anemic. You don't need to buy the drill, you can rent it. Rebar is not a problem with these, you will feel a resistance when it hits, but it'll chew through it.
These kind of tools use less than a kilowatt, so that'll give you the amps, if you're worried about that.
If you've never used one of these:
Wear eye and ear protection
Always both hands on the drill with a firm grip! the bit will seize in the hole at some point and the drill will rotate. It has a clutch, which will do its job, so you will be able to hold it with two hands, but if you hold it with one hand, you might fall off the ladder or hurt your wrist.
To drill at a 45° angle in concrete, first drill a few mm at right angle to make a starting hole so the bit doesn't slip along the wall, then slowly angle the drill to the desired angle.