Miller said he remained confident the game could be finished even using an alternative power source because the problem appeared to be outside the stadium.
"They told us that we were on the second feed, so if that feed would have been somehow interrupted then we probably wouldn't have been able to get the lights back," Miller told The Associated Press.
"That's why we're operating in (the stadium) now. That's why we're playing, because we think that we'll be able to continue. We hope to be able to continue. There's probably a problem outside the stadium."
This marked the 49ers' only Monday Night game this season and their final regular-season home game at Candlestick Park. The NFL certainly will want to make sure there are no problems when San Francisco hosts a home playoff game next month as NFC West champions.
Miller said he believes Candlestick can capably host a playoff game.
The power throughout the stadium went off about 25 minutes before the scheduled kickoff of 5:40 p.m. local time. The public address system stopped working along with everything else, so team officials encouraged media to use Twitter to reach fans and encourage them to sit tight and not panic. An emergency light quickly came on in a far corner of the stadium.