I have Charter Communications as my internet provider. For the last month or so around 7 pm to around 10-11 pm at night my internet speed goes from being 30 Mbps+ to 1-3 Mbps. My system is directly connected to the modem and no other equipment turns on around this time. I have done a virus scan and nothing there and I am confused on what the problem is.
Your problem is the amount of users on that line of cable. Charter has oversold that section and has hundreds of people on that line. From after they get home from work, download or stream until when they go to bed they all have hit on your peak performance. I would call and complain because 1-3 is way to slow.
To clarify what he was trying to say they may have oversold your node, not the coaxial cable.
Though there are a lot of potential causes for such problems. If you want to be certain do a few things test using speedtest.net and test MULTIPLE server locations and see if they all have the same problem. If they do, then you want to try pingtest.net and make sure you are not losing packets, if you are its not an oversold NODE, its a signal issue, possibly in the colder hours, which is not uncommon.