What is AC in networking?

Alternating current, commonly abbreviated as AC, refers to an electric current that reverses its direction repeatedly at regular intervals. This is in contrast to direct current or DC, which only flows in one direction. AC is the predominant form of electricity delivered to businesses and homes worldwide. But what role does AC power play in networking and telecommunications infrastructure? Read on to understand more about AC and its importance.

What is AC in networking?

AC electricity alternates between a positive and negative polarity periodically. This means the current and voltage switch directions back and forth. The rate at which this switching occurs is called frequency and is measured in Hertz (Hz).

In the United States, the standard AC frequency is 60 Hz, meaning the current changes direction 60 times per second. Most other countries use 50 Hz as the standard AC frequency.

The most common type of AC waveform is a sine wave, which has a smooth periodic oscillation between its peak positive and negative values. The voltage and current levels also follow sinusoidal patterns in AC power systems.

Compared to DC, AC can be transmitted over longer distances without substantial power loss. This makes AC the preferred method for distributing electricity through power grids. AC power can also be easily stepped up or down to different voltage levels using a transformer. This allows efficient power transmission since higher voltages incur lower losses across power lines.

Why AC power is used for networking equipment

Most networking and telecommunications equipment like routers, switches, servers, and phone systems run on AC power from the electric grid. There are several key reasons why AC is preferred over DC for powering networking infrastructure:

1. Ubiquitous and reliable

The existing electrical grid in most countries provides reliable AC power to all homes and businesses. Networking equipment can simply plug into available wall outlets to access robust and uninterrupted AC power. This avoids the need for expensive dedicated power infrastructure for networking devices.

2. Safety

AC power allows the use of lower voltages compared to DC for transmission and distribution. The most common voltage level used for AC power in the US is 120V. Such lower voltages are safer and minimize the risk of electric shocks. Networking equipment is therefore safer when running on AC compared to higher DC voltages.

3. Lower cost

The extensive existing AC power distribution system reduces costs for accessing electric power. Network devices can tap into readily available wall outlets in a building rather than installing dedicated DC power sources. This eliminates the need for additional wiring, circuits, outlets, etc.

4. Standardized

AC power is highly standardized globally in terms of voltage, frequency, outlets, wiring, and safety standards. Networking equipment can be designed to plug into standardized wall outlets and function properly worldwide. AC power provides interoperability and consistency for networking hardware.

5. Easy conversion to DC

Most networking equipment requires DC power internally for operation. While external AC power is supplied, internal power supplies convert the AC to regulated, low-voltage DC for use by the device’s components. This conversion is simple and efficient with AC inputs.

6. Improved power backup

Uninterruptible power supply (UPS) systems provide backup power from batteries in case of electricity failure. UPS units designed for AC power can efficiently supply AC outputs even when running from DC batteries. This allows seamless switching to backup power for continuous operation of networking equipment.

7. Higher power capacity

AC transmission lines can carry more power compared to equivalent DC lines due to the skin effect. This allows networking devices with high power draw like servers to function properly with AC inputs. AC power has the capacity to deliver the necessary wattage for smooth functioning of telecom hardware.

8. Resilience to outages

AC grids are designed to easily isolate faults and restore power by rerouting transmission. This provides self-healing capability and resilience to outages. Networking equipment can benefit from the reliability and uptime of AC power systems in case of external issues.

9. Easy monitoring

AC power lines allow simple monitoring of current, voltage, phase, and other parameters. Networking equipment can implement power monitoring mechanisms to track health metrics and notify administrators of any potential problems. This helps maintain uptime and availability.

10. Economies of scale

The ubiquity of AC power means components like transformers, outlets, wires, batteries, and meters can be mass produced at low cost. This benefits networking devices by ensuring cheap and widely available AC power accessories and infrastructure.

Challenges of using AC power

While AC power offers significant advantages, it also comes with some challenges that must be addressed:

  • Harmonics: Non-linear loads on the AC supply can distort the pure sinusoidal waveform, creating harmonic frequencies. These harmonics can cause overheating and performance issues. Networking equipment power supplies require AC line filtering.
  • Voltage fluctuations: Variations in supply voltage can impact equipment operation. Voltage regulators and surge protectors help provide steady AC power to networking hardware.
  • Frequency variations: In some regions, the AC frequency is not as stable as the standard 50/60Hz. Network devices must have tolerance to such frequency shifts.
  • Power factor: If the current and voltage are out of phase, the power factor reduces. Low power factor forces utilities to generate more current, increasing inefficiency. Networking equipment should have power factor correction to avoid this.
  • Noise: Electromagnetic interference (EMI) from other devices can induce noise in AC lines. This can cause data corruption and performance issues. Networking hardware requires EMI/RFI filtering for clean power.
  • Lightning strikes: Lightning events and voltage spikes on AC lines can damage networking equipment. Surge protection and isolation safeguards are necessary to protect from such events.

AC-powered devices used in networks

Some common types of networking and telecom equipment powered by AC:

  • Routers: Connect different networks such as LANs and WANs and route traffic between them. Require continuous AC power supply for high uptime.
  • Switches: Creates dedicated connections between network devices within a LAN. Require uninterrupted AC power for 24/7 operation.
  • Wireless access points: Provides Wi-Fi network access. Typically low power devices powered over Ethernet cables or AC outlets.
  • Network servers: Hosts applications, websites, files and handles network requests. Demand high AC power capacity and redundancy.
  • IP phones: Devices that enable voice over IP calls. Usually low power endpoints powered via Ethernet or AC adapters.
  • Security appliances: Firewalls, IPS/IDS systems used to monitor threats and secure networks. Require always-on AC power.
  • Media converters: Converts between different media types like fiber and copper. Draw low power easily supplied by AC outlets.

Beyond these, power-over-Ethernet (PoE) switches also use AC power to supply DC voltage to endpoint devices like IP cameras and Wi-Fi access points over Ethernet cabling.

Power backup solutions

While AC power provides reliable operation during normal conditions, networking equipment also requires backup power sources in case of electricity failure. Some common solutions include:

  • Uninterruptible power supplies (UPS): Provides battery backup that can supply AC output to networking devices for a limited time. Allows safe shutdown or switchover to standby power.
  • Generators: Onsite diesel or gas generators can supply AC power to networks when grid supply is disrupted. Provides extended backup during long outages.
  • Solar panels: Renewable solar energy systems can supplement grid AC supply and provide limited backup. Mostly used in remote areas without grid access.
  • Fuel cells: Electrochemical cells convert hydrogen fuel to DC power and supply AC using inverters. Used as silent, eco-friendly backup sources.
  • Batteries: Rechargeable sealed lead-acid or lithium-ion batteries provide DC power that can feed AC inverters for backup requirement. Compact and maintenance-free.

Properly sizing and rating backup power systems is vital for continuous operation of networking equipment when grid power fails.

AC power connectivity options

Networking devices require proper AC power cords and cables for electricity supply from outlets:

  • AC power cords: C13 and C15 cords connect equipment to AC outlets, with current ratings of 10A to 16A based on power need.
  • Cables: Direct AC cables or flexible cords are used for connections based on environment.
  • Power strips: Multiple devices can connect using AC power strips or PDUs in racks and cabinets.
  • Outlets: Wall, floor, ceiling or desk outlets of different types supply AC power where needed.
  • PoE: Switches supply AC-derived DC over Ethernet cables to devices like access points.

Typical AC power cords and cables for networking devices. Image source: Monolith

Proper AC wiring and outlets must be installed to safely deliver power as per equipment needs.

AC power best practices for networks

Follow these best practices when deploying AC power for networking equipment:

  • Carefully estimate the power budget and add at least 25% margin for future growth. Select UPS systems that can support the entire network load.
  • Install dedicated isolated electrical circuits for networking equipment to avoid interference from other electrical loads. Use filters, conditioning and surge protection.
  • Use the proper power cables and outlet types to safely deliver sufficient AC current and voltage to networking hardware.
  • Organize AC power cables neatly using cable trays, conduits and tie-wraps. Follow electrical safety codes for cable installation.
  • Place UPS systems, PDUs and backup generators in well-ventilated, weatherproof rooms with fire suppression systems.
  • Regularly test backup power systems under load to verify proper operation when required. Maintain and replace batteries periodically.
  • Monitor AC power parameters like voltage, frequency, harmonics, power factor etc. for early warning of potential issues.
  • Use rack PDUs to distribute AC power and simplify power cycling of devices. Installing remote power management enables outlet control from software.
  • Shut down non-essential network equipment during extended power outages to conserve UPS and backup generator runtime.

Following best practices for deploying and managing AC power creates a robust and resilient power infrastructure for business-critical networking systems.

The future of AC power for networks

AC power has been the de-facto standard for networking for decades and will continue to be widely used moving forward. But emerging trends are improving how AC power is generated, distributed and consumed:

  • On-site solar and fuel cells generate clean AC power complementing utility supply. Integration of renewable energy minimizes carbon footprint.
  • Smart electrical grids with two-way digital communication optimize AC power distribution using automation and data.
  • Power over Ethernet continues to evolve, supplying higher AC-derived DC voltages to a growing range of devices over existing cables.
  • Standardization of Power Delivery over USB Type-C will enable delivery of up to 240 Watts for high-powered devices.
  • UPS systems continue improving efficiency and intelligence using eco-mode, load sensing and generators with automatic start/stop.
  • Usage monitoring and analytics help track energy consumption patterns and identify opportunities for improvement.
  • Research on DC microgrids explore potential benefits of supplying DC power natively to equipment and avoiding AC/DC conversions.

While AC power has achieved ubiquity, integration of digital intelligence, renewables and improved distribution techniques will increase efficiency and resilience of future smart AC grids powering communication networks.


AC power has become the universally adopted standard for electricity transmission worldwide, finding extensive use for powering networking and telecommunications equipment. Its ability to be efficiently converted to different voltage levels, transmitted over long distances, distributed reliably to end devices, and backed up using batteries makes AC power ideal for supporting mission-critical networks. Following best practices for AC power design, distribution, redundancy, monitoring and efficiency will enable network administrators to create robust and optimized AC-powered systems that can deliver maximum uptime.

Frequently Asked Questions

1. What are the different types of AC power?
The main types of AC power are single phase, three phase, and polyphase. Single phase has a single AC waveform, while three phase uses three sinusoidal waveforms out of phase by 120 degrees. Polyphase uses multiple synchronized waveforms.

2. Does networking equipment use AC or DC power?
Most networking equipment externally connects to AC power outlets, but uses internal DC power supplies to convert the AC to usable low voltage DC levels needed by electronic components.

3. What AC power backup solutions are used for networks?
Common AC power backup options for networks include uninterruptible power supplies (UPS), diesel/gas generators, batteries, solar panels, and fuel cells. These provide temporary AC supply when utility power fails.

4. What is the standard AC voltage and frequency?
The standard AC supply voltage is 120V in North America and 220-240V in most other parts of the world. The standard AC frequency is 60 Hz in the Americas and 50 Hz in Europe/Asia.

5. How is AC power distributed from the utility grid?
AC power is distributed from the utility to end users over overhead or underground cables. Transformers used along the distribution lines step-down and regulate the supply voltage for safety and compatibility.

6. What power cables connect networking equipment to AC outlets?
Common power cables used are C13/C14 and C15/C16 cords rated for 10A, 13A or 15A of supply current. Direct AC cabling or flexible power cords are also used based on needs.

7. How does AC power backup help improve network reliability?
AC backup power from sources like generators and UPS provides temporary power when the main utility supply fails. This allows critical networking equipment to continue functioning and avoid downtime.

8. What parameters of AC power should be monitored?
Key AC parameters to monitor include voltage, frequency, harmonics distortion, power factor, load current, and total power consumption. This helps identify power anomalies and prevent issues.

9. Why is AC preferred over DC for power transmission?
AC can be transmitted with less losses compared to an equivalent DC system. AC can also easily change voltage levels using transformers, enabling efficient power transmission and distribution.

10. How does AC power get converted to DC in networking equipment?
Internal switch mode power supplies convert the external AC supply to regulated DC outputs needed by electronic components inside networking devices like routers and switches.

11. What are some best practices for AC power in networks?
Best practices include proper load planning, dedicated circuits, outlet redundancy, safety standards, neat cabling, monitoring, backup testing, remote power control, energy efficiency, and using PDUs for simpler power cycling.

12. What are harmonic distortions in AC power?
Harmonics are distortions to the pure sinusoidal AC waveform caused by non-linear loads. This can heat up transformers and wiring and cause performance issues. Line filters help suppress harmonics.

13. How does AC power redundancy improve network availability?
Having redundant AC circuits from separate power sources or backup power from UPS/generators improves availability by ensuring continuity of supply during power source failures.

14. Why is AC preferred for data centers instead of DC?
AC allows easy voltage conversion, has widely available components, and provides cost benefits from existing AC electrical infrastructure. This makes AC economical for use in data centers.

15. How does power over Ethernet work to deliver AC-derived DC?
PoE uses AC-powered switches to send DC voltage safely over Ethernet cables to devices. This removes the need for local AC power outlets at endpoints.

16. What are some key elements of AC power infrastructure?
Major elements include utility transmission lines, transformers, distribution wiring, outlets, connectors, meters, protective devices like fuses and circuit breakers, and backup sources like batteries and generators.

17. How does 3-phase AC provide more power safely?
3-phase uses three AC voltages 120 degrees out of phase. This results in more constant power delivery rather than stark peaks. It enables more power transmission for large loads.

18. Which components inside networking equipment use DC power?
Integrated circuits like processors and chips, LEDs, fans, disk drives, logical boards, and control/data circuits are some components that require low voltage DC for operation.

19. How do UPS systems provide backup AC power?
UPS systems use batteries to generate AC output when main supply fails. Double-conversion UPS always converts battery DC to clean AC output for continuous regulated power.

20. What future AC power trends will benefit networks?
Future trends like renewable energy integration, smart grids, higher PoE standards, USB-C Power Delivery, energy monitoring, and research into DC microgrids will enhance efficiency and resilience.

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