* We did not enable ad blockers, because we were testing the efficiency of the network stack, browser rendering pipeline, etc.; if you cut off ads, you're effectively skipping half the assignment. This is a valid way to improve the user experience, but not a valid way to measure browser efficiency, especially because it will disproportionately impact some sites (like the news sites that Opera's test focused on) and have no impact on other sites (like Netflix, where Edge demolishes the other browsers). It's basically skipping a lap of the race and then bragging that you finished faster.
* It's also worth noting that the ad blockers are often detected by many news sites and will actually prevent the main page content from loading at all. Not sure if Opera's test accounted for this.
* Our test was designed to mimic real-world behavior: Watching YouTube (foreground and background), shopping on Amazon, browsing the Facebook news feed, searching on Google, opening email in Gmail, and reading Wikipedia. To reduce variability, we used WebDriver to instrument the tests (supported by all four browsers tested) and made sure each task was timed rather than just a loop of consecutive tasks (which could disadvantage or advantage browsers depending on other factors like pageload performance or network conditions, in a way that doesn't reflect user experience, which is likely to linger on a page once it's loaded). We then used the Maxim 34407 power instrumentation built into the Surface Book (which is why we chose the Surface Book for this test) to measure actual instantaneous power consumption at the hardware, sampled once per second and then averaged across the duration of the test. We feel strongly that this is a highly scientific and defensible test setup which mimics typical user behavior and, significantly, measures the same markup and the same duration, on the same hardware, in every browser.