Best High Capacity HDD for NAS: Fewer Drives, Less Power

Most advice on NAS drive size stops at buying the biggest drives you can afford. That skips the part that keeps costing money after you buy: a NAS left running keeps every drive in it spinning unless it is set to spin them down. On the manufacturers’ own idle figures, 24TB of usable space takes 7.2W as two 24TB drives and 13.6W as four 8TB drives, with the same one-drive fault tolerance.

Quick picks

• Lowest idle per terabyte: WD Red Pro 26TB, model WD260KFGX. 3.6W idle, 0.14W per terabyte, the lowest figure in the table below.
• Two bays, 24TB usable: two WD Red Pro 24TB (WD241KFGX) in RAID 1, 7.2W. Two WD260KFGX give 26TB at the same 7.2W.
• Four bays, 48TB usable: three WD241KFGX in RAID 5 (10.8W), or four WD Red Pro 16TB (WD161KFGX) at 14.4W.
• Standard tier, three-year warranty: Toshiba N300 20TB (HDWG62AXZSTA). 4.41W on Toshiba’s “active idle” figure, or 0.22W per terabyte.
• Seagate: IronWolf Pro 24TB (ST24000NT002). 6.3W idle, 0.26W per terabyte.

Check the WD Red Pro 26TB (WD260KFGX) on Amazon↗

Why per terabyte, not per drive

Look at one drive at a time and larger drives seem to cost more to run. The WD Red Pro 26TB idles at 3.6W; the WD Red Plus 8TB (WD80EFPX) idles at 3.4W. But you do not buy a NAS for one drive. You buy it for a usable capacity, and you reach that capacity with some number of drives.

Divide idle watts by capacity and the drives in the table spread out, from 0.14W per terabyte (WD260KFGX) to 0.98W (Seagate IronWolf 8TB, ST8000VN004): the highest is about seven times the lowest. That is where the comparison starts. The drive count, set by your RAID level, does the rest.

Larger helium-filled drives tend to sit at the low end, but it is a tendency, not a rule:

• Brand and line can move the figure more than a step in size does. The IronWolf 16TB (ST16000VN001) is at 0.32; the smaller WD Red Pro 12TB (WD121KFBX) is lower, at 0.23.
• Some 12TB drives are about level with an 8TB. The IronWolf Pro 12TB (0.42) and IronWolf 12TB (0.43) sit next to the WD Red Plus 8TB (0.43).
• The model number matters inside one name. At 24TB, WD241KFGX is at 0.15 and WD240KFGX at 0.16; our guide to NAS hard drives covers a 12TB case where two builds under one name are much further apart.

Same usable space, different drive counts

Synology’s RAID documentation gives the arithmetic. A two-drive RAID 1 mirrors the pair and gives you the capacity of one. RAID 5 needs at least three drives and gives you the capacity of all but one. Both survive the loss of one drive, so for the configurations below the protection is the same and only the drive count changes.

With the lowest-idle drive in the table at each size a configuration needs:

24TB usable

• Two 24TB drives in RAID 1 (WD241KFGX): 7.2W
• Three 12TB drives in RAID 5 (WD121KFBX): 8.4W
• Four 8TB drives in RAID 5 (WD80EFPX): 13.6W

48TB usable

• Three 24TB drives in RAID 5 (WD241KFGX): 10.8W
• Four 16TB drives in RAID 5 (WD161KFGX): 14.4W

72TB usable

• Four 24TB drives in RAID 5 (WD241KFGX): 14.4W

At the U.S. average rate, each watt of continuous draw is about $4.81 over three years, so the 24TB gap of 6.4W is about $31 over three years and the 48TB gap of 3.6W about $17. To use your own rate, try the power cost calculator.

Among the Seagate drives in the table, the gap is closer at 48TB: three IronWolf Pro 24TB drives come to 18.9W and four IronWolf Pro 16TB to 20.0W, 1.1W apart. At 24TB it is wider: 12.6W for two IronWolf Pro 24TB against 31.2W for four IronWolf 8TB (ST8000VN004, 7,200 RPM). Seagate’s IronWolf sheet also lists a 5,400 RPM IronWolf 8TB, ST8000VN002, at 4.0W, which would make four of them 16.0W.

Two things are not in that arithmetic. The 24TB configurations mix tiers on both brands: WD80EFPX is a Red Plus with a three-year warranty and a 5,640 RPM spindle, and the IronWolf 8TB also carries three years, while the 24TB Red Pro and IronWolf Pro drives carry five. And fewer drives leave bays empty. In a four-bay NAS, a two-drive mirror leaves two bays for later; four 8TB drives leave none.

Two bays or four: what each size gets you

Turn the question around and start from the NAS you have. In a two-bay NAS running RAID 1, usable space is one drive’s capacity. In a four-bay NAS running RAID 5 across all four, it is three drives’ capacity. Using the WD Red Pro drives in the table:

• WD121KFBX (12TB): two bays give 12TB usable at 5.6W; four bays give 36TB at 11.2W
• WD161KFGX (16TB): two bays give 16TB at 7.2W; four bays give 48TB at 14.4W
• WD202KFGX (20TB): two bays give 20TB at 7.2W; four bays give 60TB at 14.4W
• WD241KFGX (24TB): two bays give 24TB at 7.2W; four bays give 72TB at 14.4W
• WD260KFGX (26TB): two bays give 26TB at 7.2W; four bays give 78TB at 14.4W
• WD240KFGX (24TB, the second 24TB build): two bays give 24TB at 7.8W; four bays give 72TB at 15.6W

Among the Red Pro drives in the table, WD161KFGX, WD202KFGX, WD241KFGX and WD260KFGX are all listed at 3.6W, so four 26TB drives come to the same 14.4W as four 16TB drives, for 30TB more usable space. The 12TB WD121KFBX in the table is lower per drive, at 2.8W. The full Red Pro sheet is less tidy: the 22TB WD221KFGX is listed at 3.4W, the 14TB WD141KFGX at 3.0W, and the second 20TB and 24TB builds, WD201KFGX and WD240KFGX, at 3.8W and 3.9W.

From 16TB to 24TB, the IronWolf Pro drives in the table do not stay flat. Four in RAID 5 come to 20.0W at 16TB, 22.8W at 20TB and 25.2W at 24TB, so on these three sizes the larger drive adds idle draw even as the per-terabyte figure falls. The IronWolf Pro 12TB in the table is listed at the same 5.0W as the 16TB. Whichever line you buy, the model number decides these figures, not the capacity label alone.

How we compared

Every drive figure on this page comes from the manufacturers’ datasheets: Western Digital’s Red Pro (January 2025) and Red Plus (September 2025) data sheets, Seagate’s IronWolf Pro datasheet DS2129.4 (November 2023) and IronWolf datasheet DS1904.21 (July 2022), and Toshiba’s N300 specification sheet (HDD-NSENA, 2024). These are manufacturer figures, not our own measurements. Toshiba lists “active idle” rather than “idle”, and its sheet does not say whether that is measured the same way as the other makers’ idle figures; the table footnotes give each drive’s source wording.

Watts per terabyte is idle watts divided by the capacity in the model name. Usable capacity follows Synology’s RAID 1 and RAID 5 formulas for drives of equal size. Running cost is idle watts × 24 hours × 365 days × 3 years at 18.31¢/kWh, the U.S. residential average for July 2026 from the Energy Information Administration. Three years is the shortest warranty among the drives in the table.

We compared 17 drives: 15 at 12, 16, 20, 24 and 26TB from Western Digital, Seagate and Toshiba, plus two 8TB drives as the baseline. It is not every high-capacity NAS drive on the market. Capacities such as 14, 18 and 22TB are not in the table, the 26TB row is Western Digital only because Seagate’s IronWolf Pro sheet cited here stops at 24TB and no 26TB N300 is in our data, and our guide to NAS hard drives covers the air-filled WD Red Pro 12TB (WD122KFBX) that we leave out here. We have also left out price per terabyte, which we cannot show, and rebuild time, for which we do not have a source we can cite.

The drives

WD Red Pro 26TB (WD260KFGX)

Western Digital · $$$$

VerdictWD Red Pro 26TB (WD260KFGX): 0.14W per terabyte, lowest in the table

Strengths

• 3.6W idle, the same figure as WD161KFGX, WD202KFGX and WD241KFGX in the table
• Two in RAID 1 give 26TB usable at 7.2W; four in RAID 5 give 78TB at 14.4W
• Five-year warranty, 550TB/year workload rating, helium-filled

Trade-offs

• The largest drive on Western Digital's Red Pro sheet, so there is no bigger step on that line
• More capacity than a 24TB usable plan needs; WD241KFGX reaches it at the same draw

It is the largest drive in the table and the lowest per terabyte, at the same idle figure as the 16TB WD161KFGX. For a two-bay machine it gives the most space for the watts: the Beelink ME Pro, for example, rates each of its two bays at 30TB, so a pair of 26TB drives fits within that.

WD Red Pro 24TB (WD241KFGX)

Western Digital · $$$$

VerdictWD Red Pro 24TB (WD241KFGX): the drive the 24, 48 and 72TB plans above are built on

Strengths

• 3.6W idle, 0.15W per terabyte
• Two in RAID 1 give 24TB usable at 7.2W; three in RAID 5 give 48TB at 10.8W
• Five-year warranty, 550TB/year workload rating, helium-filled

Trade-offs

• WD240KFGX is also sold as a WD Red Pro 24TB and is listed at 3.9W — check the model number
• 0.01W per terabyte above WD260KFGX, at the same 3.6W per drive

At 24TB, capacity plans come out in round numbers: 24, 48 and 72TB usable on two, three and four drives. Western Digital lists a second 24TB Red Pro, WD240KFGX, 0.3W higher at idle; the difference is small, but the listing’s model number is what tells you which one you are buying.

WD Red Pro 20TB (WD202KFGX)

Western Digital · $$$$

VerdictWD Red Pro 20TB (WD202KFGX): 0.18W per terabyte, at the same 3.6W as WD241KFGX and WD260KFGX

Strengths

• 3.6W idle
• Four in RAID 5 give 60TB usable at 14.4W
• Five-year warranty, 550TB/year workload rating

Trade-offs

• WD201KFGX is also a WD Red Pro 20TB, listed at 3.8W
• At the same idle draw, WD241KFGX and WD260KFGX give more capacity

It is the drive to look for if a 24TB or 26TB listing is not available: the same 3.6W, with 4TB or 6TB less per drive.

WD Red Pro 16TB (WD161KFGX)

Western Digital · $$$$

VerdictWD Red Pro 16TB (WD161KFGX): the four-drive route to 48TB usable

Strengths

• 3.6W idle, 0.23W per terabyte
• Four in RAID 5 give 48TB usable at 14.4W
• Five-year warranty, 550TB/year workload rating

Trade-offs

• 3.6W more for 48TB usable than three WD241KFGX drives in RAID 5
• Fills all four bays of a four-bay NAS

Four 16TB drives are 3.6W above three 24TB drives for the same 48TB usable, about $17 over three years, and they leave no bay free. At 16TB there is no second Red Pro build to confuse it with: the sheet lists only WD161KFGX.

Toshiba N300 20TB (HDWG62AXZSTA)

Toshiba · $$$$

VerdictToshiba N300 20TB (HDWG62AXZSTA): 0.22W per terabyte on Toshiba's active idle figure, lowest among the standard-tier drives in the table

Strengths

• 4.41W active idle
• Helium-filled, 7,200 RPM
• Available at 20TB, a capacity the WD Red Plus data sheet does not reach

Trade-offs

• Three-year warranty and a 180TB/year workload rating
• Toshiba's figure is 'active idle', a differently named measurement from Seagate's and WD's 'idle'

Western Digital’s Red Plus data sheet stops at 12TB, so above that the standard-tier drives in the table are Seagate’s IronWolf 16TB and this one. Per terabyte it is below the IronWolf 16TB (0.32), and 0.02W below the next standard-tier drive, the WD Red Plus 12TB (WD120EFBX, 0.24).

Seagate IronWolf Pro 24TB (ST24000NT002)

Seagate · $$$$

VerdictSeagate IronWolf Pro 24TB (ST24000NT002): 0.26W per terabyte, lowest among the Seagate drives in the table

Strengths

• 6.3W idle
• Five-year warranty, 550TB/year workload rating
• Three years of Seagate's Rescue data recovery listed on the datasheet

Trade-offs

• 1.75 times the idle figure of WD241KFGX at the same capacity (6.3W against 3.6W)
• Three of them come to 18.9W for 48TB usable, only 1.1W below four IronWolf Pro 16TB

If you want Seagate for Rescue, which our IronWolf Pro vs WD Red Pro comparison covers, this is the Seagate drive in the table with the lowest per-terabyte figure. Going from four 16TB drives to three 24TB drives saves less on Seagate’s IronWolf Pro sheet (1.1W) than on Western Digital’s Red Pro sheet (3.6W with WD241KFGX, 2.7W with WD240KFGX).

Compared per terabyte

Idle figures from each manufacturer's datasheet, not our own measurements. W per TB is idle watts divided by capacity. Running cost is for one drive left spinning at idle for three years. Power cost assumes continuous operation at the U.S. average residential rate, 18.31¢/kWh (EIA, July 2026).

Model	TB	Fill	Idle (W)	W per TB	Warranty (yrs)	3-yr power cost
WD Red Plus 8TB (WD80EFPX)Western Digital	8	Air	3.41	0.43	3	$16
Seagate IronWolf 8TB (ST8000VN004)Seagate	8	Air	7.82	0.98	3	$38
WD Red Pro 12TB (WD121KFBX)Western Digital	12	Helium	2.83	0.23	5	$13
WD Red Plus 12TB (WD120EFBX)Western Digital	12	Helium	2.94	0.24	3	$14
Toshiba N300 12TB (HDWG21CXZSTA)Toshiba	12	Helium	4.285	0.36	3	$21
Seagate IronWolf Pro 12TB (ST12000NT001)Seagate	12	Helium	5.06	0.42	5	$24
Seagate IronWolf 12TB (ST12000VN0008)Seagate	12	Helium	5.17	0.43	3	$25
WD Red Pro 16TB (WD161KFGX)Western Digital	16	Helium	3.68	0.23	5	$17
Seagate IronWolf Pro 16TB (ST16000NT001)Seagate	16	Helium	5.09	0.31	5	$24
Seagate IronWolf 16TB (ST16000VN001)Seagate	16	Helium	5.110	0.32	3	$25
WD Red Pro 20TB (WD202KFGX)Western Digital	20	Helium	3.611	0.18	5	$17
Toshiba N300 20TB (HDWG62AXZSTA)Toshiba	20	Helium	4.4112	0.22	3	$21
Seagate IronWolf Pro 20TB (ST20000NT001)Seagate	20	Helium	5.713	0.29	5	$27
WD Red Pro 24TB (WD241KFGX)Western Digital	24	Helium	3.614	0.15	5	$17
WD Red Pro 24TB (WD240KFGX)Western Digital	24	Helium	3.915	0.16	5	$19
Seagate IronWolf Pro 24TB (ST24000NT002)Seagate	24	Helium	6.316	0.26	5	$30
WD Red Pro 26TB (WD260KFGX)Western Digital	26	Helium	3.617	0.14	5	$17

Within each capacity the drives are ordered from lowest idle to highest. At each capacity both the lowest and the highest W per TB are at or below those at the capacity before it, but the ranges overlap: the highest 12TB figure is level with the lowest 8TB one. The 8TB rows are there as the baseline for the four-drive configurations above.

How many drives, for how much space

Each cell gives the drive size that exactly reaches that usable space, at the lowest idle figure in the table for that size. An empty cell means no drive in the table is large enough.

Use case	2 drives (RAID 1)	3 drives (RAID 5)	4 drives (RAID 5)
24TB usable	WD Red Pro 24TB (WD241KFGX)	WD Red Pro 12TB (WD121KFBX)	WD Red Plus 8TB (WD80EFPX)
48TB usable	—	WD Red Pro 24TB (WD241KFGX)	WD Red Pro 16TB (WD161KFGX)
72TB usable	—	—	WD Red Pro 24TB (WD241KFGX)

Find the usable space you need in the rows, then read across. Moving left means fewer, larger drives, lower idle draw and more free bays, and every cell has the same one-drive fault tolerance. The empty cells are where a configuration would need a 36TB, 48TB or 72TB drive, and none is in the table. Any 24TB cell can also be filled with WD260KFGX at the same 3.6W per drive, for 2TB more per drive.

If you are not sure how much space you need, the left-hand cells leave room to grow: a two-drive mirror in a four-bay NAS leaves two bays for later, and a three-drive RAID 5 leaves one. How you add drives to an existing array differs between NAS makers, so check your NAS maker’s documentation before you plan around it.

Frequently asked questions

Is it better to buy fewer large drives or more small drives for a NAS?

For idle power, fewer large drives, on the figures in the table. For 24TB usable, two 24TB drives in RAID 1 are listed at 7.2W against 13.6W for four 8TB drives in RAID 5, with the same one-drive fault tolerance. The gap depends on the line: among the IronWolf Pro drives in the table, three 24TB drives and four 16TB drives for 48TB usable are 1.1W apart.

What size hard drive should I buy for a NAS?

Start from the usable space you need and your bay count, then use the matrix above. In the table, the 26TB WD260KFGX has the lowest idle figure per terabyte (0.14W), and among the standard-tier drives the Toshiba N300 20TB is lowest (0.22W, on Toshiba’s active idle figure).

Do larger drives use more power?

Per drive, sometimes slightly: WD260KFGX is listed at 3.6W and the WD Red Plus 8TB at 3.4W. Per terabyte, larger drives in the table tend to be lower, from 0.14W (WD260KFGX, 26TB) to 0.98W (ST8000VN004, 8TB), but the IronWolf 12TB is level with the WD Red Plus 8TB at 0.43. Compare model numbers rather than capacities.

Is RAID 1 with two drives as safe as RAID 5 with four?

Synology’s documentation lists both as surviving the loss of one drive. How long an array takes to rebuild after a replacement, and what that means for risk, is outside what the datasheets and Synology’s formulas tell us, so this page does not compare it.

Does spinning the drives down change this?

It can. The comparison here assumes drives left spinning at idle. If your NAS spins drives down, standby figures matter instead, and those differ by model, so the ranking here may not hold.