In the book Wade Watts powers his Oasis console and a small heater using a battery that he recharges in a van by pedaling a stationary bike. This seems quite far fetched. The console itself appears to be a thin client with only enough CPU Aand GPU power to render the Oasis and a little extra to contribute to the server for distributed computing if needed. The power needs of such a device are likely to be quite low so i figure a regular smartphone size battery (20 to 25 watts) would be fine. However, the heater is the problem. The smallest electric heater i have ever seen is still 200 watts. A normal human can produce ~100 watts of power per hour according to this site. If the Oasis console uses ~5 watts per hour this would leave him with 95 watts with which to run his heater. That would allow him to run his heater for ~28 minutes per hour and only if he spent the entire previous hour pedaling to recharge the battery.
Yeah, I just finished the book. It was alright, It was 100% a teen book.
There must be some type of future / alternate reality tech that helps power the heater. Though a small heater would quickly warm up a tiny room, so maybe he turns it on for five minutes every hour.
As someone who read it as a teen back then, it is not a teen book. Anyone who was a teenager when that book came out would understand precisely none of the reference which is really the only apeal of the book because the prose and plot are barely even fan fiction grade.