How much power does a homelab use?
Updated
Most homelabs draw between about 50 and 350 W around the clock. Two low-power mini PCs with a 4-bay NAS, a small switch and a router average about 70 W; a three-node mini-PC cluster with a managed switch about 120 W; two used 2U servers push the lab past 300 W. Every 100 W running 24/7 is 73 kWh a month, about €22 at €0.30/kWh or $12 at $0.17/kWh.
The rule
monthly kWh = average watts × 730 ÷ 1,000
monthly cost = monthly kWh × your price per kWh730 is the number of hours in an average month (8,760 ÷ 12). Average watts is what counts: a device that idles at 110 W and reaches 220 W for four hours a day averages about 128 W.
Typical draw by device
These are the typical values the calculator below starts from; real devices vary, so measure yours at the wall when you can.
| Device | Idle (W) | Load (W) |
|---|---|---|
| Mini PC, low-power quad-core | 8 | 25 |
| Mini PC, 6–8 core | 12 | 50 |
| Raspberry Pi / single-board computer | 4 | 8 |
| NAS, 4 bays, disks spinning | 30 | 45 |
| Desktop tower used as a server | 35 | 120 |
| 1U server, older dual-socket | 80 | 160 |
| 2U server, older dual-socket | 110 | 220 |
| AI box with one 24 GB GPU | 60 | 400 |
| Switch, 8-port unmanaged | 4 | 5 |
| Switch, 24-port managed (PoE load not included) | 20 | 25 |
| Router / firewall appliance | 12 | 18 |
Three example labs
Each device busy four hours a day and idle the rest; prices at €0.30 and $0.17 per kWh.
| Lab | Devices | Average | Per month |
|---|---|---|---|
| Small | 2 low-power mini PCs, 4-bay NAS, 8-port switch, router | ≈ 71 W | 52 kWh · €15.60 · $8.90 |
| Cluster | 3 mini PCs (6–8 core) in a Proxmox cluster, 4-bay NAS, 24-port switch, router | ≈ 121 W | 89 kWh · €26.60 · $15.10 |
| Used enterprise | 2 older 2U servers, 4-bay NAS, 24-port switch, router | ≈ 323 W | 236 kWh · €70.70 · $40.10 |
Adding an AI box with a 24 GB GPU to any of them adds about 117 W on average with the same four busy hours: another 85 kWh, about €25.60 or $14.50 a month.
Work out your own
Pick your devices, set the hours they are busy, and enter your price per kWh:
Homelab power cost calculator
Typical values; real devices vary. Measure at the wall for real numbers.
Where the watts go
- Idle draw is most of the bill. In the used-enterprise lab, close to 90 % of the energy is the idle draw that runs around the clock. Cutting idle watts (newer hardware, fewer always-on hosts, spinning down disks) saves more than tuning peaks; the Proxmox power guide covers how.
- Disks add up. Every spinning 3.5-inch disk adds a few watts around the clock.
- PoE is real power. Cameras and access points powered by the switch show up in the switch’s draw, not in their own.
- The UPS has losses too, and its runtime depends on the total: check it with the UPS runtime calculator.
Sources
- RACKDENSITY calculator presets (typical idle and load watts per device class; estimates, not measurements)
- 730 hours per month = 8,760 hours per year ÷ 12
Questions
Does idle or full load matter more for the bill?
Idle, for most homelabs. Servers spend most of the day waiting, so the idle draw runs 20 hours a day or more; a high peak for an hour barely moves the monthly total.
How do I measure my homelab's power?
At the wall: a smart plug with energy metering or a plug-in power meter on the power strip, or the load reading of your UPS (on its display or with Network UPS Tools, ups.realpower). Measure for a day, not a minute, and use the average.
Does a UPS add to the power use?
A little: a line-interactive UPS loses a few percent of the load as heat, an online (double-conversion) UPS more. Add it with the UPS-losses field in the calculator.
What uses the most power in a typical homelab?
Old dual-socket servers and GPUs. One older 2U server can idle above 100 W, more than a whole mini-PC cluster with its NAS and switch; an AI box with a 24 GB GPU idles around 60 W and draws several hundred watts while generating.