What does a home server cost to run 24/7?
Start with the average watts your server draws at the wall and your electricity rate. Those two numbers tell you more about its running cost than the purchase price.
That is 2.4 kWh a day and $157.68 a year. These are calculated examples, not measured results for a particular server. Use your own rate and power measurement below.
The 24/7 running-cost formula
Annual cost = average watts ÷ 1,000 × 24 × 365 × price per kWh
Use the price in dollars in this formula: 18¢ becomes $0.18. In our calculator, enter the rate in cents instead. For a 100 W server: 100 ÷ 1,000 × 24 × 365 × $0.18 = $157.68 per year.
Include the per-kWh charges that change with usage. Keep fixed monthly service fees out of the device estimate. A time-of-use tariff needs a rate weighted by the energy consumed in each price period.
Example costs at different wattages
| Average power | kWh / year | Cost / month | Cost / year |
|---|---|---|---|
| 20 W | 175.2 | $2.63 | $31.54 |
| 50 W | 438 | $6.58 | $78.84 |
| 100 W | 876 | $13.15 | $157.68 |
| 200 W | 1,752 | $26.30 | $315.36 |
| 300 W | 2,628 | $39.45 | $473.04 |
Monthly figures use 30.44 days; annual figures use 365. Amounts are rounded to cents and shown in USD. At 36¢/kWh, each cost doubles.
Measure the workload you actually run
A momentary watt reading can miss backup jobs, media processing, and quiet hours. Record cumulative kWh over a representative period that includes those activities. If a weekly job matters, include it in the measurement.
Divide measured kWh by elapsed hours and multiply by 1,000 to get average watts. For example, 16.8 kWh over 168 hours is 100 W on average. Enter that average as both active and idle watts in the calculator, with total hours on set to 24.
Decide what you are measuring. A reading for one server covers a different set of equipment from a reading for a whole rack. Do not add the same device twice when combining measurements.
If you know active and idle power
You can estimate the two periods separately. Suppose a server uses 120 W for 4 hours and 40 W for the remaining 20 hours:
(120 × 4 + 40 × 20) ÷ 1,000 = 1.28 kWh per day
At 18¢/kWh, that is $84.10 a year. In the calculator, enter 120 active watts, 40 idle watts, 4 active hours, and 24 total hours on. A full-period meter reading is more useful when the load changes frequently.
Would a lower-power replacement pay for itself?
Compare devices doing the same job. As an illustration, replacing a 200 W average load with 40 W saves 1,401.6 kWh a year when both run continuously. At 18¢/kWh, that is $252.29 a year.
A $300 replacement takes about 14.3 months to recover its price from those electricity savings. That result changes with the measured load, tariff, and full purchase cost. It excludes maintenance, resale, financing, and heating or cooling effects.
Check that the replacement supports your workload and that you expect to keep it beyond the payback period.
Compare a replacementSources and calculation notes
Examples are Always On Cost calculations using the stated inputs; they are not hardware benchmarks. The calculator assumes the same daily schedule and rate throughout the estimate.