Red Bull and Sebastian Vettel used KERS to power to pole at Sepang on Saturday.
The team did not use the energy-recovery technology to dominate in Melbourne two weeks ago, but championship leader Vettel said he needed it to stave off a resurgent McLaren in Malaysia by just one tenth.
"We came here and solved most of the (reliability) problems," the German said. "I think if we did not have it (KERS) today, we would not be here (on pole)."
So significant has been McLaren's progress in recent weeks that Hamilton, happy to be second best in Australia, was visibly disappointed with his P2 on the Sepang grid.
"These guys (Red Bull) still have a slight edge but it seems we've closed the gap a bit," said the Briton.
Mark had a little KERS alarm that we're looking at
Also visibly disappointed was Vettel's teammate Mark Webber, but he said Saturday was a "better performance from me" after a poor showing two weeks ago.
"Mark (P3) had a little KERS alarm that we're looking at," Red Bull boss Christian Horner told the BBC, "but I don't think it was anything significant."
Vettel, meanwhile, said he thinks there will be lots of pitstops in Sunday's race given the high degradation of the Pirelli tyres.
"I hope the spectators don't lose count," he smiled.