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.
