How early should I leave NYC (Upper West Side) for EWR?
 

Original flight is at 6:00 p.m. from terminal C.

It usually takes me a little over an hour to get to EWR from the UWS (if I take the subway to Penn Station and transfer to the NJ Transit to the AirTrain).

I'm thinking, if I leave at 3:00 p.m., I could probably make it to EWR a little after 4:00 p.m. and catch the 5:00 p.m. flight, but last time I did that it was July 3 and the TSA PreCheck line was insane. I made it to my flight, but it definitely was a scramble.

Besides 7/3/19, I've never seen the PreCheck line insanely long. Has anyone been flying out of EWR consistently this summer? What was your experience like? Do you think leaving 2 hours before your flight using public transportation is sufficient?

If you're really keen on trying to make 5PM flight, I'd leave just a bit more time maybe 15-30 mins to be on the safe side, but I'm a bit of a worry-wart about these things. The only caution is while NJT normally works fine, there's random major delays that can pop up that make Penn Station a nightmare. I'm a daily commuter on NJT through Penn Station and it seems like every few weeks one these occur. Also train cancellations have become an almost daily occurrence. So if you're looking to catch a 3:47PM bound for EWR, and that happens to be cancelled last minute, then you may need to wait another 30 mins or so for the next train which might muck up your plans.

I don't mean to sound like Chicken Little here, but I'm battling PTSD from being an NJ Transit commuter. :p

1st step - check NJT website for delays before departing. You are typically okay due to frequency of service on NJCL & NEC lines even with a few delays.
If/when it works perfectly (majority of time) you will get there quickly and forced to wait at airport. Much better vs. panicking in Kearny or Harrison because you were cutting it close.

I got caught in an epic meltdown at Penn the evening of July 3, when I was trying to catch a train to Philly. Some accident in the Lincoln Tunnel led to all the Port Authority buses to NJ being cancelled, so everyone waiting for a bus walked over to Penn to try to catch a train - on top of the already high volume of regular passengers trying to get out of town on a holiday weekend. The ensuing crush of people was like nothing I've ever seen before. People couldn't get onto trains because there was literally no physical room for them. This was not helped by NJT posting a track for my train and then, once everyone pushed their way into said train, announcing that in fact the train would not be going to Trenton but was instead Long Beach-bound, or something like that. So everyone then had to fight their way off the train and back into the station, only to repeat the process later.

Another, less-extreme example: I once took NJT to EWR, but there were no Airtrains running, so they put us on a shuttle bus. Fine. However, the shuttle bus could not get into the airport grounds because someone had locked a gate across the access road the bus was supposed to travel down. So we just sat there for probably 15 minutes or so until they found someone who could unlock the gate so the bus could continue to the terminals.

These are obviously unusual situations, but I mention them to highlight the fact that NYC is basically a third-world city, and therefore you should leave extra time in your schedule in case of unexpected, third-world chaos. I personally would aim to leave Midtown four hours before my flight is due to take off, but I always err on the side of caution when it comes to travel times. But even if you're more daring than I am, I'd say 3 hours is the absolute minimum.

And I am in awe if the OP can really make it from the UWS to EWR in just an hour. I feel like the Airtrain alone can eat up 30 minutes, depending on how long you have to wait for it.

I'd corroborate the ~hour (maybe a few minutes more) from UWS to EWR, though I can't speak of recent TSA experiences. I would note that this usually involves picking a specific train, because the NJT schedules can be sporadic, especially on weekends.
In contrast, I don't usually bother looking at the schedule or targeting a specific train when taking the LIRR to JFK, as it's rarely more than 10-15 minutes between trains (other than a few times each day where there may be a 20-25m gap, and of course outside of late-night hours).

I don't go to EWR nearly as much as I used to, since UA took over CO, but back then I rarely left Manhattan more than 2-2.5 hours before my flight if taking the train. I think one time I cut it very close due to a snafu at Penn, but obviously NJT is in much worse shape than 5 years ago, so it's not unreasonable to add more time (or just fly via JFK!).

What about the bus from Port Authority to EWR; mid day on a Monday in August. Not much traffic? This is for a few people with a lot of luggage so I'm thinking the bus would be better. Would it take about an hour to get out to EWR?

I would generally recommend the train over the bus in pretty much all cases. There's room on the train for luggage, and traffic can always be a question mark.

Don't take the Bus
 

Agreed. Please do not take the bus. The roadway outside the Lincoln Tunnel is under construction so there are almost always delays.

Definitely not - as @M60_to_LGA says I would consider 3 hours the bare minimum.

At the United terminal (C) the TSA PreCheck line often looks very long but moves fast. I've never spent more than 15 minutes in that line. But I always allocate 30-45 minutes to clear security as EWR agents love making me wait 10-20 minutes after I walk through the metal detector so they can swab my phone.

Just an update as I've made this trip a few times now...

The first time I tried the train and it was a miserable experience carrying a lot of luggage. Never again! Later I drove out to a meeting just past the airport on a weekday around 10am and the traffic was not bad at all. And this past Saturday at 3pm I took the bus from Port Authority with two large suitcases and other bags and it was only about 10 minutes or so longer than taking the train. Google maps is pretty accurate now about the public transport times and it includes the EWR airport bus. So you can check maps and make your choice.

The train and Penn station is fine with only one easy to carry bag, but if you have multiple heavy bags it can be a nightmare.

I'd concur, Penn Station is just a dated mess. The core of the station was built 100 years ago, then they slapped MSG on top 50 years ago with some minor renovations over the years. I couldn't imagine trying to navigate getting down to the tracks with anything more than a simple rolling carry-on. Rush hour trains, especially North East Corridor, which stop at EWR are usually packed with pax standing in the vestibule between trains because the cars are jammed full. Track assignments are typically given last minute which causes a stampede of pax worried about missing the train or fighting to get a seat ahead of the crowd.

Off peak hours it's a little more civilized but still problematic due to the old infrastructure. The platform between the tracks are narrow and getting and accessing the tracks limited entry via stairs/escalators on the 7th and 8th ave sides. There are elevators but unless you know where they are, good luck. The whole station itself is confusing to uninitiated passengers, 7th ave side vs. 8th ave side, on the 8th ave side you've got the Amtrak area upstairs and NJT/LIRR downstairs, etc. Now there's part of the Farley post office across the street on 8th ave where you can access some of the tracks but not all.

But if you're experienced or happen to hit an off-peak time when it's not crowded without major delays and packing light, it can be very convenient getting to EWR via NJT.

Saw David Byrne of the Talking Heads a few years back huffing it to EWR with multiple bags on a packed train out of Penn Station during rush hour and he was rolling with the punches. Cool dude, I talked with him for a few minutes.

I am more experienced now, but my first time arriving by Acela I looked at all the signs I was presented walking off the train, upstairs and all around and there is not a single one that points you to the subway. You have to get a good ways from the Amtrak area before you see subway signs. Think of all the great train stations in Europe. There are always signs pointing to the subway/metro when you get off a long distance train. And I didn't know about the post office. I'll have to check that out.

He is all over New York. Lots of people have similar stories. I sat next to him in the Iridium room once, listening to Les Paul.

David Byrne is currently (through early or mid Feb I think) performing a show on Broadway called American Utopia, which is a David Byrne-choreographed concert of his music, spanning his entire career (including lots of Talking Heads music). I saw this show in New Orleans at the New Orleans JazzFest in April 2018, and enjoyed it so much that I traveled to Paris that summer to see it again (and where it was even better). I'll be seeing it a third time in NYC next week.

I highly encourage anybody who's a David Byrne or Talking Heads fan to see this show. It's great.

Yeah, it's a very confusing place and signage is terrible and very little customer service to help out confused pax. Although if you ask a regular, they'll help you out although you might need to try more than one person as it's is the kind of place where many are in a rush to get somewhere else.

A lot of inexperienced family and friends living in the suburbs ask me how to take the train into the city via NJT., First thing I say is just drive and park, if they're going to a show or Rockefeller center for the holidays and bringing kids, etc. If they insist, I give them as detailed instructions as to where to sit on the train to be in the right position for the stairways into the station and which way to go to get to either of the subway lines. Invariably, I get a call or text message saying how lost they are and sometimes can't even figure out how to get to the street.

The Iridium is a cool place, lots of good shows. I'm a jazz head and that's one of the few places to get my live jazz fix in. I used to go to the Les Paul show all the time. I dated a girl whose ex-husband was the piano player in his band and we used to get comp'ed all the time.