Windows 7: Release Candidate 1 Preview

What about battery life?

It doesn't look like Windows 7 is going to be any more power friendly than Windows Vista when it comes to power draw on desktop systems. However, that doesn't necessarily mean there won't be improvements for laptops. Microsoft has a white paper detailing some of the changes.

One item where users do have more control than in Windows Vista is in regards to LCD dimming. You can now set the delay and brightness level that your LCD will dim to before turning off completely. Some users might prefer that to seeing their screen go black if they are just pausing for a couple minutes. In terms of the true impact of this feature, however, there hasn't been any significant change that we can test in a fair way. Obviously, running your LCD at a lower brightness level will require less power, but we standardize our laptop testing at 100 nits in order to keep things equal.

What about other power saving features? A section on the idle power requirements states: "Idle efficiency is critical for the overall battery life of a PC because idle time dominates most scenarios. Reducing idle power consumption reduces the base power consumption. For example, if a portable computer uses 12W when the system is idle, all other scenarios increase power by some amount over the base 12W. Reducing idle power consumption benefits all other end-user workloads and scenarios, from DVD playback to office productivity." That makes sense, and Microsoft goes on to state, "Windows 7 provides greater idle efficiency by reducing (and in many cases eliminating) background activity on the system."

Windows 7 is supposed to improve laptop battery life by reducing CPU power requirements. One way this is accomplished is by keeping better track of what is going on in the system and reducing processor activity so that it can enter lower power states. They even claim, "In-box support of these technologies enables power-saving benefits immediately after installation." Immediate power saving benefits? If they can actually live up to that claim on the shipping version, that will be excellent. Other power saving features focus on additional peripherals, with specific mention made of networking, Bluetooth, and audio components.

With the information from the white paper in hand, we decided to conduct some power tests on three different laptops. Laptops were selected in order to cover the three primary graphics chip suppliers: NVIDIA, ATI, and Intel. For the Intel system, we used a Gateway M-7818U 15.4" notebook with GMA X4500 graphics, and the ATI system is Dell's Studio XPS 16 with Mobility Radeon HD 3670 graphics. We tested both of these systems with an OCZ Vertex 120GB SSD and a 320GB 5400RPM HDD. Finally, the NVIDIA notebook is the recently reviewed MSI GT627 featuring NVIDIA GeForce 9800M GS graphics. So let's take a look at the results....

Where's my chart!?

...or not. Simply put, we did not see any benefit to using Windows 7 at this point in time in regards to battery life, and in fact most systems had slightly lower (by a couple minutes - within the margin of error) battery life under Windows 7. We had hoped that the MSI GT627 would fare better than the laptops with ATI and Intel graphics, since NVIDIA just released their beta 185.81 driver; however, that was not the case. In fact, of the three tested notebooks the MSI GT627 fared the worst, losing six minutes of battery life relative to Vista (a change of 5% in the wrong direction).

We only had time to conduct testing utilizing our Internet battery test, so it's possible we will see improvements in other tests. Multimedia in particular has potential for improvement, as Microsoft mentions that they have invested extra time in reducing power requirements for multimedia workloads. For now, we will reserve final judgment until the shipping product.

Several notebook manufacturers have indicated that in internal testing they are seeing battery life improvements of 3% to 5% with Windows 7, and they expect with further optimizations that they will see as much as 11% to 13% better battery life relative to Vista. So what's missing right now? Microsoft's white paper again has the likely answer: "Energy efficiency requires investments across the entire platform, not only in the core hardware or in the operating system. While Windows 7 can have a significant impact on platform energy efficiency, attached devices, and non-Microsoft and end-user applications, other platform extensions often have a larger total impact. The complexity and quantity of platform extensions require a broad approach to energy efficiency beyond focusing on a single component in the platform." In short, the laptops need more optimizations focused on power management.

We have done "virgin" installations of Windows Vista on notebooks in the past, and battery life is generally worse than if we test with the laptop as it comes configured by the OEM. Some OEMs are good about providing downloadable drivers and utilities so that you can duplicate the original configuration, but right now with Windows 7 we are stuck with whatever Microsoft provides on the release candidate DVD (or through Windows Update). Hopefully the various notebook manufacturers are paying attention to this area and will have the necessary drivers and other utilities in order to get the most out of Windows 7's power management features.