Power – 120v vs 240v – AC vs DC

The standard voltage for most equipment in U.S. data centers has traditionally been 120 Volts at 60 Hertz (alternating current). However, more recently, 208V or 220/240V has become more common for high-powered equipment such as servers and storage devices, largely due to greater energy efficiency.

120V: This is typically used for smaller devices and peripheral equipment. It’s the same as the standard electrical supply in most residential and commercial buildings in the U.S.

  • Pros: Compatibility with most devices; easy to provision as it’s the standard in the U.S.
  • Cons: Not as energy efficient for high-powered equipment.

208V or 220/240V: This is increasingly common for servers and other high-powered equipment in data centers.

  • Pros: More energy efficient than 120V, leading to lower operating costs. Equipment using higher voltage also generates less heat, which can lead to reduced cooling costs and potentially longer equipment lifespans.
  • Cons: Not all equipment is compatible with these higher voltages. They can also be more dangerous due to the increased risk of electric shock, and may require special electrical installations, which can increase initial setup costs.

In addition to the power supply voltage, the use of three-phase power is common in data centers, as it is more efficient for high-powered equipment than single-phase power. This is typically delivered as 208V three-phase or 480V three-phase, depending on the size and power requirements of the data center.

Also, modern data centers are increasingly adopting direct current (DC) power distribution architectures, especially at higher power levels. DC power can be more efficient than AC power because it eliminates the need for power supply units to convert incoming AC power into DC power for use by the servers. This can reduce power losses and heat generation, but the implementation is more complex and may require special equipment.

Finally, the “right” voltage depends on a variety of factors, including the specific equipment being used, energy costs, cooling capabilities, and safety considerations. Therefore, it’s important to carefully analyze these factors when designing and building a data center.


Alternating current (AC) is the most commonly used type of electricity in data centers. AC power has been the standard in IT equipment and infrastructure for many years due to its advantages in generation, transmission, and compatibility with grid supply.

However, the use of direct current (DC) in data centers has been growing for several reasons:

Efficiency: Every power conversion (AC to DC or DC to AC) comes with some loss of power, typically in the form of heat. Many of the devices in a data center (like servers, storage systems, and networking equipment) run internally on DC. If the power supplied to these devices is AC, it has to be converted to DC, causing some efficiency loss. By supplying DC power directly, these losses can be reduced.

Reduced Cooling Needs: As DC power can lead to fewer conversion losses, less heat is produced. This reduces the cooling requirements, further increasing energy efficiency.

Simplicity: A DC power supply can be simpler with fewer components, which can potentially increase reliability and decrease costs.

Compatibility with Renewable Energy and Storage: Renewable energy sources like solar panels produce DC power. If a data center uses DC, it can potentially integrate more efficiently with these power sources. The same goes for modern battery technologies used for energy storage, which are typically DC.

Despite these advantages, DC isn’t without its challenges. Switching from AC to DC in a data center environment involves significant changes to power distribution infrastructure, which can be costly. Additionally, not all IT equipment is designed to accept DC power, especially at the scale required in a data center.

As a result, while some data centers—especially new, “greenfield” data centers—are considering or implementing DC power architectures, AC power remains the most common type of power used in data centers as of 2021. This might evolve as technology and standards develop, and efficiency becomes an even more important consideration.