This is skipped over in the movie but the novel indicates that there is some power to the stacks which is supplemented by solar pannels. Cooling isn't mentioned as a factor.
The top level or “roof” of the stacks was blanketed with a patchwork array of old solar panels that provided supplemental power to the units below.
Ready Player One - Ernest Cline
Electric cars seem to be the norm as the world has run out of fossil fuels.
As for the van where Wade/Parzival this is down to batteries charged by a stationary bike.
I dropped my backpack, shrugged off my coat, and hopped on the exercise bike. Charging the batteries was usually the only physical exercise I got each day. I pedaled until the meter said the batteries had a full charge, then sat down in my chair and switched on the small electric heater I kept beside it. I pulled off my gloves and rubbed my hands in front of the filaments as they began to glow bright orange. I couldn’t leave the heater on for very long, or it would drain the batteries.
In the movie we see Wade hook up to old car batteries
When Parzival moves up in the world he has a more reliable source of power
It had everything I wanted. Low rent, a high-end security system, and steady, reliable access to as much electricity as I could afford. Most important, it offered a direct fiber-optic connection to the main OASIS server vault, which was located just a few miles away.