Initial impression: Opera may work as claimed or could be cooking the numbers (Volkswagen, anyone?). Relying solely on Windows 10 power reports is a risky business although I've come to the conclusion that a lot of reviews and tests of laptops do exactly that, extrapolating the results from a short test (hey, I've been using it an hour and I'm only down to 90% so this battery must last 10 hours!).

On an Asus T100TAF with Windows 10, I normally get about 7 hours of battery life, running screen brightness at about 25% and using a browser (Firefox or Chrome normally), Word, a PDF viewer, and Dragon NaturallySpeaking. With Opera running currently, Windows is reporting that I have 87% battery capacity after about 1.5 hours of use with 7.5 hours remaining, but as is normal for many battery meters, the readings have fluctuated--at 95% capacity, I was informed that I had 10.5 hours of battery remaining.

Opera tells you that the power saving mode is off by default, but it's simple to turn on. In addition, you must run the included ad blocker to get the full savings, but I have no problem doing that. As you might expect, using the blocker means pages load pretty quickly.

To do an honest report, I'm going to have to run the computer solely with Opera to depletion, then repeat with FF and Chrome. That will take some time, and I'm not absolutely certain I have the patience to surf the web for that long a time at any one sitting so I'll probably take a week or so before providing a full report.

Any suggestions on refining my testing methodology are certainly welcome.