The psi is irrelevant for this job because the nozzle and how far you hold the wand from the surface will determine it.
Power wash siding psi.
A pressure washer can quickly ruin vinyl siding by cracking it with the high pressure stream of water so it s necessary to know which pressure level and nozzle to use.
A standard gasoline or electric washer with a pressure rating around 3 000 psi should provide more than enough force to effectively clean even hard to reach places.
Starting low and gently working your way up is the safest bet.
To rent or buy.
You will want a power cleaner with at least 2 3 gpm.
Perform a few test sprays on one of the lower corners of the siding to help you get used to the power.
All the pressure washers with 2 3 gpm have at least 2 600 psi.
This model is a gas powered pressure washer with a flow rate of 2 5 gpm and a maximum water pressure of 3 200 psi.