Most businesses know what their computers cost to buy and almost none know what they cost to run. Measuring real consumption, instead of relying on nameplate ratings or rules of thumb, shows where the money goes and which changes are worth making.
Start with the arithmetic
The calculation is simple. Multiply a device’s power draw in watts by the hours it runs, divide by 1,000 to get kilowatt-hours, then multiply by the electricity rate. A 100-watt device running 10 hours a day, for example, uses one kilowatt-hour daily. U.S. Energy Information Administration data put the national commercial average near 14 cents per kilowatt-hour in early 2026, with the lowest-cost states closer to 7 to 9 cents. Use the blended rate from your own bill instead, since demand charges and tiered pricing can make the effective cost differ from a published average.
Measure at the wall, not from the label
A power supply’s wattage rating is a ceiling, not a measurement. To learn actual consumption, plug the computer into an inexpensive watt meter or an energy-monitoring smart plug, and record the draw in each state: off, asleep, idle, and under a typical workload. Include the whole desk, because monitors, docking stations, and speakers draw power as well. Sample across a full working week, and use metered power strips or PDUs for server racks. ENERGY STAR applies the same logic when it certifies computers, weighting measured power in off, sleep, and idle modes by assumed time in each to estimate yearly energy. A business can do the same with its actual working hours.
Idle power is where waste hides
Consider an illustration, with the assumptions stated plainly. A desktop averages 40 watts while powered on and 2 watts asleep, and electricity costs 14 cents per kilowatt-hour. Left on all year, it uses about 350 kilowatt-hours and costs roughly $49. If it sleeps outside a 50-hour work week, it uses about 116 kilowatt-hours and costs roughly $16, a saving near $33 per computer. Across 50 computers, that is about $1,600 a year. Energy.gov, citing ENERGY STAR, estimates savings of up to about $30 per computer each year from sleep features, which sits in the same range.
Equipment efficiency and replacement decisions
Efficient hardware helps, though less than people expect. Energy.gov reports that ENERGY STAR labeled computers use 30 to 65 percent less energy than unlabeled ones, depending on usage, and that laptops use much less energy than desktops. Apply 30 to 65 percent to the $49 example and the annual saving is roughly $15 to $32 per machine. That rarely justifies replacing a working computer early, but it is a sound tiebreaker at refresh time. Favor ENERGY STAR certified models, consider laptops and docking stations for staff who do not need desktop power, and include monitors, which draw very little when certified and asleep.
Practical energy-management decisions
Start with settings, which cost nothing. Push sleep and display timers centrally through Group Policy or Microsoft Intune, matching them to real work patterns. Check that overnight patching and remote access still work, since sleeping machines must wake for updates; scheduled wake times or Wake-on-LAN usually solve this. Computers also release heat, so lower power draw can trim cooling needs in warm months. Ask your utility whether it offers incentives for efficient equipment or power management, and review the numbers again after a year, using the original meter readings as the baseline. Report results as dollars per workstation per year, so decision makers can weigh energy against other IT priorities.
Want to know what your office computers really cost to run and where you can cut waste without disrupting staff? Our team can measure your fleet, set up centralized power management, and plan efficient hardware refreshes. Get in touch to start.