Simple energy estimateNAS Power Cost Calculator
Apply measured or vendor-listed power draw to operating hours and your electricity price.
Formula
Watts ÷ 1000 × hours × days = kWh. The calculator multiplies energy by the price you enter.
This is not a utility-bill calculator. Tiered rates, fixed charges, taxes, seasons, and whole-home use vary by location. Use the result to compare the incremental cost of a NAS.
Improve the estimate
Drive sleep and workloads vary. A smart-plug average measured for three to seven days is more useful than a maximum power rating.
Related checks
Compare capacity by drive count and review the hard-drive buying checklist.
Formula and units
Average watts ÷ 1000 × operating hours per day × days per month gives monthly kWh. Multiply by your entered price per kWh; annual cost is twelve times the monthly estimate. This models the incremental device load.
Worked examples
Always-on two-bay NAS
At 25 W, 24 hours, 30.4 days, and $0.16/kWh, the estimate is 18.24 kWh and $2.92 per month. Use a low value only when drive sleep is proven reliable.
Always-on four-bay NAS
At 45 W under the same assumptions, the estimate is 32.83 kWh and $5.25 per month. Measure at the wall to include UPS conversion losses.
Home server for 12 hours
At 80 W for 12 hours over 30.4 days, energy is about 29.18 kWh. Weigh scheduled shutdown against missed jobs and extra drive cycles.
How to interpret the result
A small monthly saving does not automatically justify aggressive drive start-stop cycles. Compare devices using the same measurement point and period. Purchase price, UPS cost, and replacement drives remain separate from electricity.
Error sources and limits
Tiered rates, fixed charges, taxes, seasons, and whole-home demand vary by utility. Choose either a blended bill rate or the marginal rate for added use and state that assumption. A vendor maximum-watt figure is not an average.
Frequently asked questions
Will this match my utility bill?
No. It estimates incremental device cost rather than reproducing the entire tariff.
Can I enter sleep-mode watts?
Use a three-to-seven-day average that includes both workload and sleep periods.
Does this include the UPS?
Only when your measurement is taken at the wall upstream of the UPS.
Last reviewed: 2026-08-21