Actually checked up on this for myself, you can limit it following this guide:
http://superuser.com/questions/1039229/limit-bandwidth-used-by-windows-update
If you want a short version:
right-click and make a text file and paste the following in, change extension to .reg and open it, allowing it to modify
Code:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\BITS]
"EnableBITSMaxBandwidth"=dword:00000001
"MaxBandwidthValidTo"=dword:00000001
"MaxBandwidthValidFrom"=dword:00000006
"MaxTransferRateOffSchedule"=dword:00000100
"MaxTransferRateOnSchedule"=dword:00000100
Change the MaxBandwidthValidFrom as starting time, ending in e.g. 23 for 11pm, same for to, in my case it's from 6am to 1am.
MaxTranfserRateOff/OnSchedule is the speed it's allowed to download in Kbps, I limited it to 100Kbps. Windows update mostly keeps to it, averaging about 200Kbps now due to spikes of 400Kbps and goes back down to 100Kbps.