Server Power Supply Efficiency
In general, the more efficient a power supply is, the less energy you use overall. If you operate multiple servers on the same rack, the savings on electricity costs can add up significantly over the course of a year.
Titanium power supplies offer 96% efficiency, making them the most efficient option. Platinum power supplies are slightly less efficient, at 94%. Gold power supplies provide lower efficiency, at 92%.
The efficiency of a power supply is calculated based on how much input AC energy (or, in some cases, DC) is required to produce a certain amount of output energy. For example, a power supply that requires 200 watts of input to produce 180 watts of output will have an efficiency of 90% (180/200 = 0.9).
The difference of 20 watts between input and output is lost as heat. In addition to the extra cost of producing this wasted energy, another disadvantage of inefficient power supplies is that this heat must be managed: you will need cooling equipment to remove it.
Of course, the efficiency of a power supply is not linear or constant across its entire output range. Most power supplies operate at maximum efficiency when running in the upper ranges of their capacity. This means that an 800-watt power supply delivering 400 watts of power (50% capacity) will be less efficient than a 500-watt power supply delivering the same output power of 400 watts (80% capacity).
Why Is This Important?
Efficiency is an important factor when choosing a power supply, but you need to consider more than just the efficiency rating of the power supply. By correctly estimating the power consumption of your server system, you can select a properly sized power supply that will operate at optimal efficiency.
In large data centers (enterprise), cumulative energy losses caused by multiple servers running on inefficient power supplies can be significant. To get the most accurate measurement possible, it is often helpful to configure and measure the actual system under load in advance. However, this method may not be practical for many customers, as it involves purchasing, configuring, and operating each component of the server system. As a result, smaller customers who cannot perform such tests may sometimes end up using a power supply larger than necessary.
Redundant Power Supplies
Redundant power supplies are used as a backup in case the main power supply fails. Having redundant power supplies is crucial to ensure operational continuity in the event of a main power supply failure.
Regarding redundant power supplies, each server operates differently. Some servers will use the main power supply for 100% of the energy needs until it fails, at which point they will switch to the secondary power supply. Others will balance power requirements between the two supplies. It is also possible to configure how you want the server to use the two power supplies.
Server Performance and Power Supply Efficiency
On one hand, the efficiency rating of a power supply can give you an idea of how it will perform. At the same time, the specific server with which the power supply is used can impact its efficiency.
As shown in this case study, the same power supply can operate with different efficiencies on two different servers. This particular study showed that the Dell PowerEdge R720 server performed more efficiently than the HP ProLiant DL380p, but it is clear that this can vary from case to case.
How Much Does It Cost to Operate My Server?
It is important to consider both the noise level and the operating cost of a specific power supply.
This helpful chart compares cost and noise levels generated by various servers for certain power supplies.
There is a simple formula you can use to calculate the power costs of your server. Multiply the watts by the hours of usage (per day, month, or year, depending on preference) and divide the result by 1,000. Then, multiply the result by the electricity cost per kilowatt-hour. The result will be an estimate of the total cost for operating that power supply.
Get Help Choosing the Right Power Supplies
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