Power Supplies

Which supply fits my server

A server takes only the supplies its maker lists for its generation, so start from the server rather than the wattage. Dell and HPE document these families:

Dell's R750 technical guide calls the 60 mm and 86 mm supply the new form factor of its 15th-generation design, and its R740 manual rules out supplies from earlier PowerEdge generations, so a supply from one generation is not a spare for the next.

Redundant power supplies: what has to match

A redundant pair works only when both supplies match, and Dell's PowerEdge R740 manual sets four rules for it:

• Two installed PSUs must be the same type and have the same maximum output power.
• PSUs from previous PowerEdge generations are not supported in the pair, even at the same power rating.
• AC and DC supplies cannot be combined.
• AC supplies take 120 V or 240 V input, except Titanium supplies, which take 240 V only.

On HPE servers, the QuickSpecs make Flex Slot one common form factor across ProLiant Gen9 and Gen10, except that Low Halogen (LH) Flex Slot units do not fit Gen9, so check the generation a supply is rated for.

Mixing and upgrading wattage

A PowerEdge server enables only matched supplies. Dell's R750 and R760 technical guides describe the check: with two supplies present at power-on, the server compares their wattages, enables the larger one if they differ and posts a mismatch warning in the BIOS, iDRAC or LCD, and a supply added to a running server comes online only when its wattage matches the installed one. To move to a higher rating, replace both supplies with a rating Dell lists for that server.

Efficiency classes

An efficiency class is a set of measured efficiencies at several loads, and Dell's R760 technical guide publishes the targets for its redundant supplies:

Choosing the wattage

Order the same wattage as the supply already in the server, because both units in a redundant pair must have the same maximum output. To see what a configuration draws at idle, typical and peak load, read our power guides for the PowerEdge R740 and the R750, and our R760 PSU specifications.

Supplies for switches and storage arrays

Network switch supplies are listed separately under network switch power supplies, and supplies for Dell storage arrays sit with the other storage array power supplies.

Server power supply questions

Can I mix a 750 W and an 1100 W supply in one server?

Not as a working redundant pair. Dell's R740 manual requires both supplies to have the same maximum output, and Dell's R750 and R760 guides describe what happens otherwise: at power-on the server enables only the larger supply and posts a mismatch warning, and a mismatched supply added while running is not enabled. HPE warns that mixing different Flex Slot supplies may limit or disable power supply features.

Can I install higher-wattage supplies than the originals?

Yes, if the rating is one the maker lists for that server and both supplies match. Dell lists several ratings per generation, from 495 to 2600 W on its 14th-generation servers, for example, so a pair can move up together. Replace both units at once, since Dell will not enable a hot-added supply of a different wattage, and check the power draw in our guides.