system
Given the following post, respond as if you're commenting on Reddit:
human
[Spider-Man: Homecoming] What powers Spidey's suit?

Minor spoilers:

What is the power source for Spider-Man's Stark-provided suit? There's enough juice to run a JARVIS-level AI, a holographic HUD, various enhanced sensors (like thermal and x-ray vision), cameras that record everything the mask sees, a spy drone ...

It's Stark-tech, so my first guess would be an arc reactor, but we've never seen one smaller than a hockey puck, and there's a distinct lack of big-glowing-disk anywhere on Spider-Man's suit.
gpt
A mixture of dynamos and the ultra-efficient batteries that Stark uses to power most of his silly gadgets like the glovewatch and his glasses.

Peter has Super-Strength. Tony designed the suit to resist Peter's movements to a degree, both as a way to charge the suit's batteries through kinetic force and to restrict his combat ability. This is why he's less graceful than he might otherwise be in the redblue, and why some suggest his Spider-Sense isn't very present while wearing it. It is - the suit's just fighting him without him realizing.

This kinetic resistance is the reason Peter messes up a few times - most notably during Civil War he mentions the suit messing up his landing, while in Homecoming he misses that one support structure.

Both of those can be attributed to the dynamos charging the suit. The batteries themselves are embedded in the same layer as the chip he pulls out. This kind of stuff shouldn't matter for what Stark wants him to do (neighborhood shit) but is irritating otherwise, and likely can be toggled off for important fights as needed.

Probably the biggest change in Iron Spider (the suit at the end) is transferring to a distributed Arc power system, allowing both more advanced weapons/tech to be implemented and less resistance in the same overall package.