Effective limits on internet use/iPhone use for teen

We also have a 14 year old. We allow 2 hours a day with the phone at the same time each evening and on weekends we add 2 hours a day playing games on iPad. 

Enforcing this is simple. We say the phone and pad need to be handed in to parents after the time is up (as opposed to parents having to beg or demand he turn it off). If he is late handing it in he loses 15 minutes the following day. It only took one 15 minute loss before he became meticulous about the hand-in. 

This is may seem overly rigid for some parents but we came to this amount of screen time and these particular consequences after a year of non-stop battles over the phone. We saw that our child would literally choose to not eat, not bathe, not speak to anyone in the family, never leave his room if he had the option of being with a screen instead. 

Because of this we ignored all of the protests about how we were ruining his life and he would have no friends and how boring and meaningless his life would be.

None of these disasters he predicted came to pass and now we have a normal, relatively happy teenager again. 

Yes, we are struggling with this too, as most of us probably are. We have had the best success so far with the iPhone parental controls that can set screen time limits. We find having a technological way of limits that happen on their own is way better than keeping tabs on usage ourselves and trying to get our teens to comply.  If you and your kid both have iPhones, you can set up Family Sharing, if you haven't already, where you're the Organizer or Parent and they are the kid.  Then you can set Screen Time limits (different ones for different apps) and Downtime (a schedule when all apps become inoperable).  The kid can request extra time if they run out and you can approve it for a length of time or deny it.  We found that making up the limits collaboratively helps them have buy-in. It doesn't work perfectly, but it helps.  It doesn't help with computer use, however.

I have a 14 and 16 year old.  I'm interested in hearing others' responses, but this is what we've done.  This system is in response to our 16 year old being completely addicted to screens to the point where she (unbeknownst to us) would routinely stay up until dawn bingeing Netflix, You Tube, Tik Tok etc for 8+ hours straight and then sleep until 4 in the afternoon.  Now we allow them three hours of screen time each per day, but each hour has to be earned.  They get one hour for waking up by a certain time, one hour for going outside and doing something active for at least 30 minutes, and one hour for doing an agreed-upon academic activity like a math worksheet.  We have limits on their phones and the computer so they can't use them unless we unlock it.  And we take all the phones, laptops, iPads, Nintendo switch controllers, etc. and put them in a tote bag under our bed every night after we learned that they figured out a way to have all the screen-time limits "reset" at midnight.  Texting and listening to music is the only thing I leave unlocked on their phones - during quarantine I don't want to take away their one opportunity to connect with their friends, and so far texting has not been a problem.  I honestly feel like screen time is like heroin sometimes, by the way my kids will do literally anything to try to sneak it and completely lose their minds when we set limits on it.  Good luck, it is SO hard and we have had to be extremely strict with this plan, but it has worked for us and we feel like a relatively normal family again.  When school starts we are going to limit screens even further, ugh wish us luck...

Are you just limiting use of the phone?  Or are you providing something else for you teen to do?  Makes no sense to limit time and offer nothing to do in exchange. 
We haver four kids.  Neve limited or restricted use.  We believe not limiting screen time had a positive effect.  Allowed them to be comfortable with technology, be informed about Internet scams and people who might want to cause them harm, which is allowing them to develop their critical thinking skills.  This has allowed them to easily spot conspiracy theories and not become a victim of a cybercrime.

But if you want to restrict Internet/iPhone use the only way to do that is to take the computer and phone away.  If you try to impose any restrictions through software your kid will just go online and figure out how to defeat it in less time then it took for you to set it up.

Did we make the right decision by not limiting screen time?   Our kids graduated from UC. Berkeley, Brown, Sonoma State, and the other is at UC Davis?  Is that success?
One more thing not limiting screen time did was burn our kids out on games.  Yes they played games, but then they reached a point where they lost interest and hardly play them anymore.

Let me give you something else to consider.  I am college professor teaching STEM classes and dual enrollment classes at the high school.  The students who are very confotable with technology have a much easier time in my classes compared to the students who had limited access to technology.  Students struggle with the subjects I teach which is hard enough.  But the ones who had limited use of technology not only do they struggle with what I'm teaching them they also have to learn how to use the technology at the same time.  It is so frustrating for the students.  I see these students struggle and every semester I lose students became they aren't comfortable  with the technology.  And I lose more women then men.  And it usually far more devastating for women.

Hope you give some thougth to what I have posted.

I have a successful college student and I never limited her screen time, but she had to finish her homework, sports, and chores before she could lay around and watch videos. She had some missteps along the way (oops, and still does sometimes), going to bed way too late because of tik tok and then having to rush off to work and take a nap later. She basically learns her own lesson when that happens, which is a much better result than me enforcing it. I always let her know that after her required duties were completed that her time was then her own. Plus, we are now on shelter in place, what is your daughter going to do? Go on a walk by herself? Perhaps a daily requirement would be that all of you - as a family - go on an hour walk every day, pull weeds, make cookies, read a play.