A NAS is the classic “set it and forget it” homelab box — which is exactly why its power draw quietly adds up. The good news: for most people it is one of the cheapest things in the rack to run, as long as you understand where the watts actually go.
The short answer: a typical home NAS draws 6-40 W depending on how many drive bays it has and how many disks are active. At the US average of $0.17/kWh, that works out to roughly $9-60 per year for the NAS itself. The single biggest variable is not the NAS board — it is the spinning hard drives.
What does a NAS actually cost per year?
Running cost is just average watts × hours × your price per kWh. Here are real-world figures from our wattage database, assuming 24/7 operation. The “typical” column blends idle and active draw the way an always-on box really behaves.
| NAS class | Typical draw (24/7) | US $/yr (0.17) | UK £/yr (0.25) | Germany €/yr (0.40) |
|---|---|---|---|---|
| 2-bay consumer (DS224+) | ~10 W | $14.89 | £21.90 | €35.04 |
| 4-bay Intel (TS-464) | ~30 W | $44.68 | £65.70 | €105.12 |
| 4-bay Ryzen (DS923+) | ~35 W | $52.12 | £76.65 | €122.64 |
| DIY 6-bay TrueNAS tower | ~55 W | $81.91 | £120.45 | €192.72 |
Estimates at 24/7 operation. Source: HomelabWatts wattage database, data as of 2026-06-14. Run your own numbers in the cost calculator.
The pattern is clear: a small 2-bay box is genuinely cheap to leave on — under $15/year in most of the US. A power-hungry DIY tower with six spinning disks can cost 5-6x more for the same job, mostly because of the drives.
Why the drives matter more than the box
The NAS motherboard, SoC and RAM in a modern appliance idle very efficiently. The variable cost is the disks:
- Each active 3.5-inch HDD draws roughly 4-8 W, plus a short spin-up surge of 15-25 W.
- 2.5-inch and SSD drives draw far less — about 1-4 W with no spin-up spike.
- A 4-bay box full of 3.5-inch drives can spend more power on disks than on the NAS itself.
This is why the manufacturer’s “access” power figure is so much higher than the “HDD hibernation” figure. The same DS923+ might draw 10 W with drives spun down and 35 W with all four active. Spin-down is your biggest lever.
How to cut a NAS power bill without turning it off
You rarely need to power a NAS off — you need it to spend more time in its low-power states. In rough order of impact:
- Enable drive hibernation / spin-down for idle periods. The catch: chatty services (Docker logging, indexing, snapshots, an external tool polling SMART every minute) can keep drives awake. Audit what touches the array.
- Consolidate write-heavy junk onto an SSD. Put logs, Docker volumes, download scratch and metadata on a small SSD so the big HDDs can actually park.
- Right-size the pool. Six 3.5-inch drives “just in case” is six idle watts each forever. Fewer, larger drives draw less than many small ones.
- Schedule it if your access pattern allows. A NAS used only in the evenings can be woken with Wake-on-LAN — running 8 hours a day instead of 24 cuts roughly two-thirds of the energy.
For the wider rack, see our guide on reducing homelab power consumption.
Is a NAS even the expensive part of your lab?
Usually not. Compare the figures above with a used enterprise server idling at 90-110 W (that’s $134-164/year in the US) and a NAS looks like a rounding error. The boxes that dominate most homelab bills are old rack servers and oversized custom builds, not storage appliances — see idle vs load watts: why the difference matters and our mini-PC vs rack server 3-year cost breakdown.
The bottom line
For a small 2-bay NAS, electricity is a non-issue — budget around $10-15/year in the US, a bit more in Europe. The cost climbs with drive count, so the way to keep it low is fewer, larger drives that spend most of their time spun down, not powering the unit off. Plug your own model’s wattage and your local kWh price into the calculator for an exact figure.