Teklanika campground in Denali Park has additional limitations that the other campgrounds at Denali don't have.
Minimum stay is three nights. Fresh water is available, outhouses are good, but there are no other services. For instance, there is no firewood available at the campground.
Generator usage is limited to a few hours a day; this is strictly enforced. Idling your vehicle to charge batteries is not permitted either. During our stay, some RVers left early because they didn't have generators and their batteries were not robust enough to keep the furnace going for three days in the chillier temps. One RVer's batteries went so low he could not put his slide in.
Once you arrive at Tek and park, that's it ... you're parked for the three days. If you pull out of the campground to return to the entrance, you cannot return unless you book another three day stay. Thus you need to take firewood in with you, and ensure you have enough fresh water for your stay. Also be sure to empty your black/grey tanks before going in.
Thus the Tek bus pass is purchased before you go into Tek. The pass is valid for the three days you're at the campground. You can hop onto the park school bus tours (if there's a seat) for a ride into the park. You cannot take the buses out to the park entrance and then return. Once you're out, you're out. Reserve the Tek pass at the same time you reserve your campsite.
Campsites are first-come, first-serve. If you have a larger RV, this might be a challenge. It is best to arrive early in the day to have a better selection of campsites left empty by those departing. Some tenters take the longer deep sites for more privacy which is a pain if you're an RVer with a long rig. When we arrived there were only two sites available suitable for our truck & 25' fifth wheel. Fortunately, one of them was much to our liking, right along the river.
Teklanika is a great spot to camp. Much quieter than the others because there are no lookie-lous driving through as only those with paid-for Tek campsites are permitted to drive their vehicle that far into the park.
For folks wishing more flexibility about driving in & out, the Savage River campground is also pleasant. It is bigger and busier, but also nice. Same limited services but campers aren't required to stay 3 nights and you can come & go whenever.
Another rule that was a bit frustrating ... those needing to walk their dogs are limited to roadways. Dogs are not permitted on any of the hiking paths, to keep the impact on the wildlife minimal. It was a bit tough for us as they were also working on the park road so it was muddy and soft. They were also applying some sort of gooey stuff that made it nasty on all of our feet. So we made a lot of laps of the campground with our dog!