The Good/Bad settings may or may not help, it really depends on the hardware. Some settings are marginal, others save a fraction of a Watt, others may actually not help at all. Here is some analysis I did late 2011. I used a high precision digital multi-meter and an Atom 450 "HPMini 210-1000" and a Sandy Bridge "Lenovo ThinkPad 220i" machine to sanity check all the powertop settings for the candidate machines.

Powertop tunables that resulted in gains

• Autosuspend for USB device HP Webcam-50: 2.6%


• Wireless power saving for interface wlan0: 8.5%


• Wireless power saving for interface wlan0: 0.5%


• Autosuspend for USB device Broadcom Bluetooth device: 6.4%


• Enable SATA link power management for /dev/sda: 0.4%


• Enable Audio codec power management: 0.5%


• Runtime PM for PCI device Intel 2nd gen Core proc. DRAM controller: 1.0%


• Runtime PM for PCI device Intel 6 series/C200 HD audio controller: 1.2%


• Runtime PM for PCI device Intel 82579LM gigabit network connection: 0.4%


• Runtime PM for PCI device Realtek RTL8188CE 802.11b/g/n WiFi adapter: 0.4%


• Runtime PM for PCI device Ricoh e823: 0.4%

Powertop tunables that resulted in losses

• Runtime PM for PCI device Intel N10/ICH 7, PCI Express port 1: 0.2%


• Runtime PM for PCI device Intel N10/ICH 7, PCI Express port 2: 0.3%


• Runtime PM for PCI device Intel N10/ICH 7, USB UHCI controller #2: 0.2%


• Runtime PM for PCI device Intel N10/ICH 7, USB UHCI controller #3: 0.3%


• Runtime PM for PCI device Intel N10/ICH 7, USB UHCI controller #4: 0.1%


• Runtime PM for PCI device Intel 2nd gen Core proc. graphics controller: 1.5%


• Runtime PM for PCI device Intel 6 series/C200 MEI controller #1: 0.7%


• Runtime PM for PCI device Intel 6 series/C200 PCIe root port 1: 0.7%


• Runtime PM for PCI device Intel 6 series/C200 PCIe root port 2: 0.6%


• Runtime PM for PCI device Intel 6 series/C200 PCIe root port 4: 0.6%


• Runtime PM for PCI device Intel 6 series/C200 PCIe root port 5: 0.5%


• Runtime PM for PCI device Intel 6 series/C200 USB EHCI #1: 0.3%

source: http://kernel.ubuntu.com/~cking/power-benchmarking/powertop-good-bad-recommendations/results.txt

raw sample data: http://kernel.ubuntu.com/~cking/power-benchmarking/powertop-good-bad-recommendations/powertop-good-bad-recommendations.ods

Fluctuations in battery reading

Note that powertop tries to figure out the power consumed from the battery ACPI status. Some batteries are not that accurate since they sometimes re-calibrate their capacity settings. So one can get some wild fluctuations in battery readings. With the kind of settings you are looking at powertop may not be able to measure the savings because we could be talking about a few mW in savings on each setting.

For big savings, see https://wiki.ubuntu.com/Kernel/PowerManagement