A hose and a pressure washer are not the same tool for this
For ordinary dirt, dust, and the light haze new concrete sometimes shows the first time you sweep it, a garden hose and a broom do the job just fine once the slab is walkable, usually within a couple of days of the pour. That is low pressure, spread over the whole surface, and it does not push water into the concrete any faster than rain would.
A pressure washer is a different scale of force aimed at a small spot at a time. On concrete that has already cured, that is not a problem. On concrete that is still working through the curing process, that same force can drive water deeper into a surface that has not closed up yet, and can etch or dull a finish that has not fully hardened.
Why the surface is still vulnerable that first month
Concrete does not dry the way a puddle dries. It cures, a chemical reaction between cement and water that keeps building strength for weeks, and the surface is at its most porous and least hardened in that early window. That is the same reason we tell people to keep sprinklers and hard rain off a slab the first couple of days, and it is the same reason a pressure washer needs a longer wait than a hose does.
A washer used too soon can also strip or scar a decorative or stamped finish before it has had a chance to fully set up, which is a cosmetic mistake that is hard to undo later.
The fork: general cleaning versus a real stain
If the concrete just looks dusty, dull, or has a little construction residue on it, ordinary sweeping and a hose rinse handles that without any wait beyond the slab being walkable. There is no reason to reach for a pressure washer for routine cleaning on new concrete at all.
If something has actually stained the surface, oil, rust, mulch, or tannins, pressure washing it early does not fix that any faster and risks doing more damage than the stain itself. Wait the month, and if a stain is still there once the slab has cured, that is a question worth a call rather than a guess about how much pressure to use.
If the slab is sealed, wait again
A sealer needs its own time to cure once it is applied, and pressure washing a slab too soon after sealing can lift or streak the sealer instead of cleaning the concrete underneath it. If your patio or driveway was sealed, ask when we tell you it is ready rather than going by the concrete's own cure timeline alone, because the sealer resets that clock.