A home server running 24/7 costs about $16 a year at 10 watts, $32 at 20 watts and $160 at 100 watts at the 18.31¢ US average residential rate (EIA, July 2026). The rule behind every number below is simple: annual cost = watts ÷ 1,000 × 8,760 hours × your rate per kWh. That is our arithmetic. Most small NAS boxes and mini PCs sit in the 10 to 40 watt range, so their electricity costs less than the drives you put in them. The hardware is the real bill.
Yearly Electricity Cost by Wattage and Rate
A server that runs all year uses 8,760 hours of power. The table below applies the formula at five rates: 10¢ (cheap), 15¢, 18.31¢ (the US average per the EIA’s July 2026 table), 25¢ and 35¢ (just above California’s 33.61¢ in the same table).
| Average draw | kWh per year | 10¢ | 15¢ | 18.31¢ | 25¢ | 35¢ |
|---|---|---|---|---|---|---|
| 10 W | 88 | $9 | $13 | $16 | $22 | $31 |
| 20 W | 175 | $18 | $26 | $32 | $44 | $61 |
| 35 W | 307 | $31 | $46 | $56 | $77 | $107 |
| 50 W | 438 | $44 | $66 | $80 | $110 | $153 |
| 75 W | 657 | $66 | $99 | $120 | $164 | $230 |
| 100 W | 876 | $88 | $131 | $160 | $219 | $307 |
Divide by 12 for a monthly cost. At the US average, a 10 W server is about $1.34 a month and a 100 W one about $13.34. The jump from 10 W to 100 W costs $144 a year at that rate. It costs $276 a year at 35¢.
What Real Devices Draw
The “average draw” is the number that matters, not the label on the power brick. These are the figures we found, each from the page named:
- Synology DS224+ (2-bay NAS): 14.69 W in access mode and 4.41 W in HDD hibernation, per Synology’s spec page.
- Synology DS925+ (4-bay NAS): 37.91 W in access mode and 12.33 W in HDD hibernation, per Synology’s spec page.
- Intel N100 mini PC (Beelink MINI S12 Pro): 7 to 10 W idle headless, 20 to 21 W under sustained load, per StarryHope’s test notes.
- Beelink EQ14 mini PC: 11.8 W idle under Windows, per Igor’s Lab testing.
Synology’s numbers show how much hibernation matters. At the US average rate, the DS224+ costs about $23.56 a year in access mode and $7.07 a year if its drives were spun down all year. Hibernation only applies while nothing is using the drives. A machine that serves media, runs backups or hosts containers keeps them awake, so budget closer to the access-mode figure.
Older desktop PCs reused as servers are a different story. We did not find a sourced idle figure for them, so measure yours with a plug-in watt meter. Our appliance electricity cost guide explains how to read a meter and rank devices around the house.
Hardware: What You Pay Up Front
Prices below are what we found in early October 2026, and several are from retailer or review pages that update daily. Check current listings before you buy.
| Item | Price | Source and note |
|---|---|---|
| Synology DS224+ (2-bay) | About $299 | B&H’s usual price as reported by Android Central, with sales at $239 |
| Intel N100 mini PC | $179 to $249 | StarryHope’s Beelink MINI S12 Pro listing, depending on RAM and SSD |
| WD Red Plus 4 TB | $194.99 | Amazon US, as pulled by ComputingForGeeks on 27 September 2026 |
| WD Red Plus 12 TB | $459.99 | Amazon US, same pull |
| APC Back-UPS BE600M1 | $99.99 | Markertek, list $140, out of stock when we checked |
ComputingForGeeks also notes that the 8 TB WD Red Plus had dropped off Amazon entirely, so capacity choices are narrower than usual. We did not verify why. The drive prices are the point to watch: two 4 TB drives cost $390, more than the NAS enclosure.
What a Whole Setup Costs
Here is a two-bay Synology with two 4 TB drives and a small UPS, our arithmetic from the table above:
- Enclosure: $299
- Two WD Red Plus 4 TB at $194.99: $390
- APC BE600M1: $100
- Hardware total: about $789
Add five years of electricity at the DS224+ access-mode figure of $23.56 a year, which is $118, and the five-year total is about $907. Electricity is roughly 13% of it. An N100 mini PC with its own SSD and the same UPS is $279 to $349 in hardware (our arithmetic), plus about $80 over five years at 10 W and 18.31¢. If you add external drives to the mini PC, price those separately.
Drives: The Hidden Variable
Drive count matters more than the label on the box. More bays means more spinning platters and more watts, which is part of why the DS925+ lists 37.91 W against 14.69 W for the two-bay model. Both are Synology figures for different products, not a per-drive measurement, so we do not state a watts-per-drive number. When you plan capacity, a single large drive uses less power than two smaller ones, but it gives up redundancy. The 12 TB WD Red Plus at $459.99 is $38.33 per terabyte, against $48.75 per terabyte for the 4 TB at $194.99 (our arithmetic).
UPS: Protection That Costs Twice
A UPS protects the drives and file system from sudden power loss. The APC BE600M1 is rated 330 W and 600 VA, which covers the NAS and mini PC figures above with room to spare. It costs about $100 up front, and the battery will need replacing eventually (we did not find a price for the replacement, so we left it out). A UPS also draws some power of its own, which we could not find on the page we checked. Our vampire power guide covers standby draw and why small always-on loads add up.
How to Cut the Bill
- Measure first. A plug-in watt meter shows the real average. Specs are a starting point.
- Choose fewer, larger drives. Each spinning drive adds power.
- Let drives spin down if your workload allows. Synology’s own figures show a threefold difference.
- Use the lowest-power machine that does the job. A mini PC at 10 W costs $16 a year at the US average. An older tower at 100 W costs $160.
Bottom Line
A home server costs about $16 to $160 a year in electricity at the 18.31¢ US average, scaling linearly with wattage and with your rate. A two-bay NAS with drives and a UPS costs about $789 up front by our arithmetic, so over five years the hardware is the main cost and power is a smaller line. Measure your actual wattage, then use our electric bill estimator to convert it to dollars at your rate.
FAQ
How much does it cost to run a NAS 24/7?
A two-bay NAS like the Synology DS224+ draws 14.69 W in access mode per Synology, which is about $23.56 a year at 18.31¢ per kWh. A four-bay DS925+ at 37.91 W is about $60.80 a year. Both are our arithmetic from Synology’s spec numbers.
How much electricity does a mini PC use as a home server?
Test notes put an Intel N100 mini PC at about 7 to 10 W idle, which is $11 to $16 a year at the US average rate. Under sustained load the same machine drew 20 to 21 W, about $33 a year. Your actual draw depends on the SSD, network adapter and what the server runs.
Is a NAS worth the electricity cost compared with an old PC?
It can be. The two Synology models cost $24 to $61 a year in access mode, while any machine drawing 100 W costs $160. Over five years that gap is about $500 against the larger model, which can pay for the NAS enclosure. Measure your PC first, since idle draw varies a lot.
Do I need a UPS for a home NAS?
A UPS is not required, but it protects the drives and file system from sudden power loss. The APC BE600M1 costs about $100 at Markertek and is rated 330 W, which is more than a typical NAS or mini PC uses. Whether it is worth it depends on how often your power flickers.