Two things
> First of all, you say 10% -30%, but what do these percentages mean in real terms? Ie how much is 100%.
> Secondly, how much the explorer is used depends on what processes are running. Check which processes are running and which ones of them are on explor based processes. Then you can decide whether it is too much or no.
Also, if you have a low-power processor (2 Ghz or less), 10% -30% is not much at all, but if you have a modern high-power processor (3.5 and higher GHz), then 10% -30% can be really too high.
One of the common causes is damaged programs, malicious programs, or Windows itself, so they do not close (remain run in the background as suspended processes) or some processes cannot start properly and Windows tries regularly something to open.
Such things can also be caused by unknown background processes, such as malware, but also searching for updates and installing updates, or if Windows attempts to log in to something, but cannot, etc. Sometimes may cause such athings third parti antivirus and anti malware programs etc.
So, here is too little data to think out something and suggest something at all. You must look, what runs and what uses explorer. Also, how clean is Windows itself, how clean and compact is the registry. Is the Windows itself OK. Have You scanned it using sfc.exe /scannow (recommended run in administraor privileges, if not, it may not able to fix some errors).
So if You have something more specific, let us know. I think somebody is always available who can help.
Good luck!
