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A Guide to SIP Trunking vs PRI: Pros and Cons, Benefits & TCO Breakdown

A Guide to SIP Trunking vs PRI: Pros and Cons, Benefits & TCO Breakdown

In some ways, PRI and SIP phones both serve the same core purpose: allowing employees at the enterprise to place and receive business phone calls.

Primary Rate Interface (PRI) is an interface standard used to deliver multiple voice lines over physical copper lines that are part of your building’s physical infrastructure. 

Session Initiation Protocol (SIP) trunking is a technical standard that supports VoIP calls by initiating and ending calls between a VoIP line and the PSTN.

While both PRI and SIP have their uses, "which is best" could be neither today. With newer technology being deployed nationwide, advancements are available that can drive your organization's communications with minimal changes for both on-premises and remote employees. 

Check out some of this new technology here.

SIP Trunking vs. PRI


What is PRI Phone Service?

PRI is a T-1 transmission technology that has been widely used to support voice communications for over 40 years.

A PRI circuit includes 23 voice channels to support 23 concurrent calls and one data channel to support call-related functionality like caller ID. Voice calls supported through PRI technology are submitted as electrical pulses and routed through traditional telecommunications carriers. 

Traditional telephony requires a relationship with a telecommunications company and on-site servicing of cabling to add lines or upgrade equipment.

PRI is an alternative to IP-based phone technologies, including SIP trunking.

Pros of PRI

  • Does not rely on data bandwidth to support voice calls
  • High quality via dedicated line structure
  • It can be made redundant via the addition of a second PRI circuit for failover

Cons of PRI

  • PRI is expensive to implement and upgrade and requires costly monthly phone service
  • May require long-term contracts with traditional telecom companies for local and long-distance calling
  • Requires dedicated capacity that can only be purchased in 23 line units
  • Slow to scale, modifications to infrastructure may take weeks of waiting

Best Uses Cases for PRI Technology

  • Organizations with legacy PRI infrastructure and limited access to fiber-optic internet connectivity or sufficient bandwidth to support IP-based phones.
  • Hybrid PRI and SIP trunking implementations, where organizations retain legacy PRI technology for local calls while using SIP for multimedia communications and saving costs on long-distance/international calling.

What is SIP Trunking or a SIP Phone?

SIP supports the transmission of voice calls as data and other types of multimedia communications. SIP is a phone technology, but it supports the transmission of Unified Communications, including video conferencing, SMS messages, data transmissions, and more.

For organizations with hosted phone communications, SIP trunking equipment is generally hosted and maintained by the vendor to manage the transmission of voice data. SIP is an alternative to PRI in that it eliminates the need for traditional phone infrastructure, including circuits.

Pros of SIP Trunking

  • Sold by vendors on a per-channel basis on-demand, so you only pay for the capacity needed
  • Much cheaper; cost savings vary but can be as much as 30-40% cheaper than PRI phones
  • Offers failover to mobile phones in case of loss of office data connectivity
  • Includes easy-to-use administrative portals for easy management
  • May be offered via the cloud as part of a Unified Communications (UC) implementation
  • Can be integrated with multimedia communications for collaboration and productivity
  • Offers simple support for multiple sites and remote workers
  • May include rich mobile features and mobile-first design
  • Integrates with PRI phone lines for hybrid phone systems

Cons of SIP Trunking

  • Requires internet bandwidth, ideally business fiber internet, to support quality of service (QoS).
  • Needs sufficient network information security, like firewalls, to prevent cybercrime risks.
  • The quality and extensibility of service offered by hosted VoIP vendors can significantly vary.

Best Use Cases for SIP Technology

  • Saving money on business phone service, especially for organizations with long-distance and international outbound calling.
  • Cost-effective support for contact centers.
  • Adding mobility features to the enterprise and supporting remote workers.
  • Reducing the burden of phone system management on internal IT personnel.
  • Moving towards hosted, multi-channel cloud communications or Unified Communications as a Service (UCaaS)
  • Gaining the ability to quickly scale business communications by adding and removing lines and features on-demand.

SIP Trunking vs. PRI: Which is Best for Businesses?

PRI and SIP Trunking are two competing approaches to phone technology that each carry distinct advantages and disadvantages. There is no one right answer. Your best fit will depend on the particular needs of your business when it comes to telephony.

For many organizations, SIP trunking to support VoIP telephony or UCaaS is the smarter choice. It enables access to the benefits of significant cost savings, improved collaboration tools, and better reliability.

For other firms, a hybrid approach to using both PRI and SIP is the right decision. Educational institutions may decide to implement unified communications, but maintain a few PRI lines to support legacy intercom technology and some disaster recovery planning scenarios. 

For other businesses still, PRI may be the right choice.

Head to Head: SIP Trunking vs. PRI on 4 Key Business Considerations

1. Cost

For the vast majority of organizations, SIP is much cheaper than PRI. Cost is an important consideration for organizations, even though it’s not the only factor to consider when you’re investing in a business phone system. 

Organizations that need to scale their system, add features, and perform long-distance calling will likely achieve massive cost savings.

There are very rare instances where PRI may be less costly than SIP. These use cases are generally limited to small, brick-and-mortar businesses with no need for advanced phone features like eFax or integrated messaging. 

For organizations that aren't growing or adopting different communication technologies, maintaining an existing PRI system could be the right choice.

Going a little deeper on total cost of ownership (TCO), here's what you need to consider:

Initial Setup Costs:

PRI trunking entails higher initial setup costs due to dedicated hardware. In contrast, SIP trunking solutions offer significant upfront savings by eliminating the need for expensive PRI hardware.

Maintenance and Upgrades:

PRI trunking may incur ongoing maintenance expenses, while Atlantech Online's SIP trunking solutions require minimal maintenance and seamless upgrades without costly hardware replacements.

Potential Savings:

SIP trunking provides competitive pricing and flexible models, enabling businesses to pay for what they need and consolidate services for additional cost reduction.

ROI and Business Value:

In most cases, SIP trunking solutions deliver tangible benefits, including improved efficiency and scalability, resulting in a higher ROI and sustainable growth.

Who wins? SIP Trunking most of the time.

2. Information Security

PRI is considered more secure, which isn’t strictly correct. Copper cabling can be subject to many information security risks, including interference and interception. 

However, organizations that lack the on-site information security expertise to achieve adequate network security and attempt to run consumer-class VoIP over public internet connectivity may be very vulnerable to security risks.

Who wins? SIP Trunking with adequate network security.

3. Flexibility

The biggest con to PRI is also among the greatest pros of SIP trunking; flexibility and scalability. With PRI, organizations are required to purchase additional user capacity in 24 lines. 

With SIP, organizations can add a line for a service month to accommodate a temporary or seasonal employee and remove the line as soon as it’s no longer needed. 

SIP can enable organizations to unlock truly usage-paid billing on-demand, while organizations using PRI may need to wait weeks to schedule a technician for very high-cost infrastructure upgrades.

Who wins? SIP Trunking takes the victory when it comes to flexibility for your business.

4. Reliability

The reliability of copper-based phone cabling can be damaged by a number of risks, including inclement weather, vandalism, or simple degradation of aging infrastructure.  

While PRI is considered a very reliable technology, and it generally is, organizations will lose access to phone service if a component of their infrastructure is damaged.

SIP is reliable, provided organizations partner with a reliable vendor and invest in fiber-optic internet connectivity, which is very resistant to weather and other common types of damage. 

With mobile failover, organizations can continue using dedicated phone lines even if data connectivity is lost on-site.

Who Wins? It depends. SIP Trunking is more reliable in most cases, but some organizations may prefer a hybrid approach.

5. Deployment Timelines

When it comes to deployment time, SIP trunking outshines PRI trunking in terms of speed and efficiency.

For example, Atlantech Online's SIP trunking solutions can be provisioned and activated in as little as a week thanks to our streamlined deployment process and extensive network infrastructure.

Whether you're upgrading your existing phone system or implementing a new communication solution, our team ensures a seamless transition with minimal lead time. With SIP trunking from Atlantech Online, you can enjoy the benefits of advanced communication technology without the delays associated with traditional PRI installations.

Who Wins? SIP trunking.

Is SIP Trunking vs PRI Best for My Business?

Ultimately, it depends on your organization, goals, and desire to adopt next-generation communication and collaboration features. 

The majority of organizations today have adopted or plan to switch to VoIP phones and UCaaS as a tool for cost savings, better value, and business agility. While PRI is the right choice for some select organizations, many firms find that SIP beats out traditional PRI phones.

For more information to help you ensure you’re making the best choice for your business, refer to our free resource, 10 Questions to Ask Before Buying Phone Service

This free ebook will provide you with all the key considerations you should evaluate when choosing the right phone service for your business and deciding between SIP trunks vs. PRI.


Tom Collins
Post by Tom Collins
May 9, 2024
Tom is the Director of Enterprise Sales & Marketing for Atlantech Online. He has over 20 years of professional experience in the Internet Service Provider industry and is known for translating technology into positive results for business. A native of Washington, DC, a graduate from University of Maryland (degrees in Government & Politics and Secondary Education), Tom is also a five-time Ironman finisher.