14 DAY TRIAL // The Surface Book is Microsoft's first laptop ever and unsurprisingly, just like any first-generation device, it is affected by a number of problems that have already been confirmed by many buyers, including one that's causing huge battery drain in sleep mode.
Microsoft confirmed that it's aware of the issue and explained that it's already working on a fix, but this won't arrive sooner than early 2016.
In other words, yes, the battery drain during sleep mode is a known bug and yes, a fix is on its way, but no, you won't get it in 2015.
Websites streaming content at fault
Basically, the bug is impacting battery life once the Surface Book is switched to sleep mode by closing the lid, but according to Microsoft itself, very often a number of processes continue to run in the background and lead to this unexpectedly huge battery drain.
“Yes, The ‘standby’ battery life is an issue we are working on and have been working on. We can put the processor into a deeper sleep state than it is currently set to. We couldn’t do it at RTM for a variety of reasons, power management is a very hard computer science problem to solve especially with new silicon. Currently it is not in the deepest 'sleep' that it can be so there are wake events that would not otherwise wake it. We will have an update for this issue sometime soon in the new year,” a company engineer called Joe said.
He also provided some guidance in order to help users avoid this problem until the fix arrives and recommended everyone to close any website that's streaming content before putting the device into sleep mode. Websites that stream sounds, such as YouTube, are often the ones leading to the battery drain, so make sure you shut them down before closing the lid of the laptop.
This isn't, however, the only major bug that needs to be fixed on the Surface Book. Some models are getting stuck with a BSOD when detaching the screen, but for the moment, no workaround is available for this one and Microsoft is yet to confirm whether it's a known bug or not.