DeepMind reduced Google data center cooling bill by 40% in an experiment. If this effect is real, it probably more than justified the $500m tag Google paid to acquire DeepMind. Google might not have come up with a killer app, but perhaps the real killer app is not in the consumer space.
To be fair, the HN discussion was mostly focused on the lack of substantial details or an actual research paper to back up that claim. Google would probably need to show that only DeepMind, or an equivalent device, would have been presently likely to find the energy savings that it ended up finding.