One other potential area of variability could come from browser extensions - I imagine that users who compare browser power performance are more technical than

One other potential area of variability could come from browser extensions - I imagine that users who compare browser power performance are more technical than the median user, and are more likely to run browser extensions (e.g. ad blockers, etc). Given Chrome has a larger and more extensive collection of extensions, perhaps users who see differences are running more browser extensions in their Chrome installation, which impacts on performance/power usage? Certainly interesting to see these assumptions put to the test though, and get some data around them. While it looks like it may have fallen behind again a little, I noticed Firefox's browsing performance on Speedometer caught up for a while, contrary to what I had thought/assumed.