"Overnight (~8 hours) unplugged, I lost 8% of the battery, but doing a sleep study showed that it actually DID go into a low-power state, for 99% of the time it was asleep, for the first time ever," said someone identified only as dmills6788 in a thread on Microsoft's own support forum. "So in that respect it worked, and will probably keep it from getting super hot and kicking the fan on."
Others echoed that conclusion. "Completely fixed," said act94, who posted an image of a power consumption test.
The Surface Book -- as well as the Surface Pro 4 -- have been plagued with sleep issues since their launch last fall. Users said the devices did properly enter a sleep mode, but stayed on, draining their batteries and making the notebook and tablet hot to the touch.
Microsoft was aware of customers' complaints, but offered only a very general timeline for a fix: "Some time soon in the new year."
On Dec. 3, a Surface engineering team program manager, flagged only as "Joe," acknowledged, "We can put the processor into a deeper sleep state than it is currently set to." Joe went on to say that Microsoft wasn't able to do that by the time the Surface Book and Surface Pro 4 released. "Power management is a very hard computer science problem to solve, especially with new silicon," he said.
On the forum, some customers scoffed at Joe's characterization of power management as a "very hard" problem.
Yesterday, Microsoft issued an update for the Surface line, including the Surface Book and Surface Pro 4. Several of the individual components of the update were described as improving "stability during power state transition changes into and out of sleep states."
As has become Microsoft's habit, the company said next to nothing about the fixes included in the update, nor did Panos Panay, the executive who leads the Surface group, offer details in a blog post Wednesday.
But a Microsoft employee identified as Josh_F elaborated briefly on the support forum. "Along with other improvements, this update addresses several previously noted issues related to power management, specifically Connected Standby," said Josh_F.
"Connected Standby" is Microsoft's label for technology that lets a device in sleep mode continue to receive notifications and email, even when the notebook or tablet is running in a low-power mode. Apple's similar feature in OS X is called "Power Nap."