Distinguish screen-off from system sleep
ENERGY STAR’s computer guidance emphasizes power management and explains that screen savers do not provide the same savings as low-power states. A display can turn off while the computer continues downloads, processing or a running game.
Check the operating-system settings and the behavior you observe after the chosen timeout. If a work application prevents sleep, account for that actual state rather than calculating the advertised sleep figure for hours the machine never spends asleep.
Compare two hypothetical overnight states
Suppose a computer averages 3 W asleep and 0.5 W shut down while still plugged in. The difference is 2.5 W. Over 12 hours on 365 days, it equals 10.95 kWh, worth about $1.97 at $0.18/kWh.
These are illustrative inputs. By contrast, leaving the same hypothetical machine at 50 W idle instead of 3 W asleep for those hours would add 205.86 kWh, costing about $37.05. Verifying sleep can matter more than refining an already tiny off-state load.
Measure the state you intend to change
Use a suitable meter over a long enough period to resolve small loads, with a device connection allowed by the equipment instructions. Record whether peripherals and a powered dock are included. Check that scheduled activity did not wake the machine during the test.
An overnight measurement is a description of that particular night. Repeat if updates or other unusual tasks made it unrepresentative.
Keep work requirements in view
Save work and allow a normal shutdown when that routine suits your needs. Sleep may offer convenient resumption; scheduled tasks may require another arrangement. For an employer-managed computer, follow the organization’s settings and update requirements. Compare the modest energy difference with the routine you can reliably maintain, and prioritize preventing long periods of unintended active idle before buying hardware solely to reduce a few watts of standby.
Choose your next step
Continue with the question that matches your next decision:
Sources & further reading
Numerical examples are illustrative unless explicitly described as measured. This guide does not claim hands-on product testing. Read the methodology and editorial disclosure.