ATX 400W Power Supply — Best 400 Watt PSU for Servers & Workstations in 2026
Find the right ATX 400W power supply for your server or workstation. Sparkle, FSP, Seasonic compared. 80 Plus ratings, connector types, and tower server PSU compatibility.
ATX 400W Power Supplies — Still the Sweet Spot
The 400-watt ATX power supply remains one of the most requested PSU wattages for tower servers, workstations, small form factor builds, and desktop-class servers. It provides enough power for a single Xeon processor, 64-128GB of RAM, 4-6 hard drives, and a low-profile GPU — without the excess wattage (and cost) of a 600W+ unit.
Typical applications include Dell PowerEdge T130/T140/T340 towers, HP ProLiant ML110/ML310 towers, Supermicro workstation towers, and custom NAS builds.
How Much Power Do You Actually Need?
| Component | Typical Draw |
|---|---|
| Intel Xeon E3 (4-core) | 65-80W |
| Intel Xeon E5 (8-core) | 85-135W |
| DDR4 RAM (per 16GB) | 3-5W |
| 3.5" HDD (per drive) | 6-10W |
| 2.5" SSD (per drive) | 2-5W |
| Motherboard + fans | 40-60W |
| Low-profile GPU | 25-75W |
| Total (typical tower) | 250-350W |
A 400W PSU provides comfortable headroom for a standard tower server build. The general rule: your PSU should run at 50-80% of rated capacity for maximum efficiency and longevity.
Top 400W ATX Power Supplies
| Brand | Model | Wattage | Efficiency | Form Factor | Price |
|---|---|---|---|---|---|
| Sparkle | ATX-400PN | 400W | 80 Plus | ATX | $25-40 |
| FSP | FSP400-60THA | 400W | 80 Plus | ATX | $30-45 |
| Seasonic | SSP-400ET2 | 400W | 80 Plus Bronze | ATX | $40-55 |
| EVGA | 100-N1-0400 | 400W | Standard | ATX | $25-35 |
| Dell | L400E-S0 | 400W | 80 Plus Gold | ATX (Dell specific) | $20-35 |
| HP | DPS-400AB | 400W | 80 Plus | ATX (HP specific) | $20-35 |
80 Plus Efficiency Ratings
| Rating | Efficiency at 50% Load | Annual Savings vs Standard |
|---|---|---|
| Standard (no rating) | ~75% | Baseline |
| 80 Plus | 80% | ~$8-12/year |
| 80 Plus Bronze | 85% | ~$15-20/year |
| 80 Plus Gold | 90% | ~$25-30/year |
| 80 Plus Platinum | 92% | ~$30-35/year |
For a server running 24/7 at 250W draw, the difference between a standard PSU and an 80 Plus Gold unit is roughly $25-30 per year in electricity savings. Over a 5-year server lifespan, that is $125-150 — which often exceeds the price difference between PSU tiers.
ATX Connector Types
A standard ATX 400W power supply includes:
- 24-pin ATX — Main motherboard power (always included)
- 4+4 pin EPS — CPU power (required for all servers/workstations)
- SATA power — Drives (typically 4-6 connectors)
- Molex (4-pin) — Legacy peripherals and fans (2-4 connectors)
- PCIe 6-pin — GPU power (included on some 400W units, not all)
Pro Tip: If your tower server uses a proprietary PSU form factor (common with Dell OptiPlex, HP EliteDesk, Lenovo ThinkCentre), a standard ATX PSU will not fit. Check your chassis dimensions and connector layout before ordering.
OEM Server PSU Replacements
Many tower servers use standard ATX form factor PSUs with brand-specific part numbers:
| Server | OEM Part Number | Wattage | Replacement |
|---|---|---|---|
| Dell PowerEdge T130 | NFRTK / 9J6JG | 365W | Standard ATX 400W |
| Dell PowerEdge T140 | TVRVR | 365W | Standard ATX 400W |
| Dell PowerEdge T340 | 1GX31 | 495W | Standard ATX 500W |
| HP ML110 Gen10 | 867927-001 | 350W | HP-specific form factor |
| HP ML310e Gen8 | 671310-001 | 350W | HP-specific form factor |
Pro Disk Network carries ATX power supplies from 250W to 1600W, including OEM Dell, HP, and Lenovo server PSUs. Every unit is tested under load before shipping. Contact sales@prodisknetwork.com for PSU compatibility verification.