PBX Telephone Systems Explained: On-Prem vs Cloud PBX (UK Guide 2026) Quick answer
A PBX (Private Branch Exchange) telephone system is a business phone system that manages internal and external calls.
In 2026, most UK businesses now choose Cloud PBX or hosted VoIP systems instead of traditional on-premise PBX hardware because they are:
cheaper to deploy
easier to scale
better for remote working
simpler to manage
Traditional PBX systems still exist, but they are now mainly used by businesses with specialist infrastructure, legacy systems or strict on-site control requirements.
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Contents
What is a PBX Telephone System?
Types of PBX systems
PBX Telephone System Providers
PBX telephone system costs
PBX and SIP trunking
Traditional PBX vs. VoIP PBX: Pros and Cons
Considerations to Make When Choosing a PBX System
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Authored by: Ally Cox (Business Technology & B2B Services Specialist 10+ Years’ Experience)
Reviewed by: James Ward (Telecoms Specialist, 12+ Years Experience)
Last Updated: May 2026
Key Takeaways
PBX systems manage business calls internally and externally
Traditional on-prem PBX requires hardware and higher upfront cost
Cloud PBX delivers PBX features via the internet on a monthly basis
Most UK SMEs now choose Cloud PBX or VoIP systems
SIP trunking is often used to modernise existing PBX setups
Cloud PBX is better suited to remote, hybrid and growing teams
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What are PBX Telephone Systems?
A PBX telephone system is a private telephone network used within a company or organisation that allows internal and external communication, connecting phones within said organisation while also enabling them to make and receive external calls. PBX systems can be either traditional, using analogue lines, or modern, leveraging digital VoIP (Voice over Internet Protocol) technology.
Here is a table outlining some of the differences of these systems:
Feature Traditional PBX (analogue) Modern VoIP PBX
Technology Analogue phone lines (POTS)
Internet Protocol (VoIP)
Deployment On-premise hardware
Cloud-based or on-premise
Scalability Limited scalability
Highly scalable
Cost High upfront costs for hardware and maintenance
Lower upfront costs, potentially lower ongoing costs
Features Basic features like call forwarding, voicemail
Advanced features like video conferencing, call recording, mobile apps
Maintenance Requires in-house IT expertise or service contracts
Minimal maintenance required for cloud-based systems
Reliability Relies on traditional phone lines, susceptible to outages
Less susceptible to outages, can often have disaster recovery options
Security Secure closed network
Requires strong security measures for VoIP calls
Integration Limited integration with other business applications
Integrates easily with various business tools and software
Types of PBX systems Traditional (on-premise) PBX
A physical PBX system installed in your office, connected to phone lines or ISDN (now largely retired in the UK).
IP PBX
An on-site PBX that routes calls over an internet connection rather than analogue phone lines.
Cloud PBX (Hosted PBX)
A PBX system hosted in the cloud by a provider. No on-site PBX hardware is required.
Hybrid PBX
A mix of on-premise hardware and cloud services, often used during phased migrations.
PBX Telephone System Providers
Provider Overview Key Features Cost Reviews
NEC Established brand known for reliability and advanced features
On-premise PBX systems, scalable solutions, robust call management, voicemail to email
Avaya
Leading provider offering a wide range of PBX solutions
On-premise, cloud, and hybrid options, integrations with various business tools, advanced security features
Reliable provider with a focus on user experience
On-premise and cloud-based PBX systems, user-friendly interfaces, mobile apps, collaboration features
3CX (On-premise option)
Open-source platform offering flexibility and customization
Cost-effective, on-premise deployment, supports multiple devices, requires technical expertise
Free (up to 5 extensions)
Paid plans start at a one-time cost
Gamma
Established provider with excellent UK support
Feature-rich hosted PBX, easy to manage, integrates with business applications
Contact for a quote but there is a free plan available
Traditional PBX Telephone Systems vs. VoIP PBX: Pros and Cons
Feature Traditional PBX VoIP PBX
Uses internet
No
Yes
Supports remote staff
Limited
Excellent
Video calling
Rare
Common
CRM integrations
Limited
Extensive
Mobile apps
Rare
Standard
Ongoing maintenance
High
Low
Call flexibility
Moderate
High
PBX vs Cloud PBX
Feature Traditional PBX Cloud PBX
Installation
On-site hardware required
No hardware on-site
Upfront cost
High (hardware + install)
Low or none
Monthly cost
Lower ongoing, higher maintenance
Per-user monthly fee
Scalability
Limited, hardware dependent
Instantly scalable
Remote working
Limited
Built-in
Maintenance
Internal or paid support
Included with provider
Future-proofing
Poor
Strong
PBX telephone system costs in the UK (2026) Traditional PBX costs
Hardware: £1,000 – £10,000+
Installation & configuration: £500- £3,000
Ongoing maintenance: £50 – £300 per month
Additional costs for expansion or changes
Cloud PBX costs
Typically £10-£25 per user per month
Minimal setup fees (often included)
Maintenance, updates and support included
Easy to scale up or down
For many businesses, Cloud PBX offers a lower total cost of ownership over time.
PBX and SIP trunking Businesses that already own a PBX system often modernise it using SIP trunking, and SIP trunks replace traditional phone lines and allow calls to be routed over the internet while keeping existing PBX hardware which is common for:
Warehouses
Manufacturing sites
Call-heavy offices with legacy systems
Considerations to Make When Choosing a PBX System
What are your primary communication needs? How many users to do you have (and anticipate having)? VoIP is better for larger organisations with many users Following on from that, consider your scalability needs and future growth predictions. Remember that traditional PBX requires more on-site IT expertise for setup and maintenance.
Who PBX systems are best for Traditional or IP PBX systems may still suit businesses that:
Have existing PBX infrastructure
Operate from a single fixed location
Require full internal control of telephony
Have specialist compliance or security needs
Who should avoid traditional PBX You should usually avoid installing a new on-prem PBX if you:
Have remote or hybrid staff
Expect headcount to change frequently
Want predictable monthly costs
Prefer minimal IT maintenance
In these cases, we think that Cloud PBX or VoIP systems are almost always a better fit.
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PBX telephone system costs
Cost Type Typical Cost
PBX hardware
£1,000-£10,000+
Installation
£500-£3,000
Ongoing maintenance
£50-£300/month
Expansion costs
Often expensive
Cloud PBX Costs
Business Size Typical Monthly Cost
Small business
£10-£20/user/month
Mid-size business
£15-£30/user/month
Enterprise
£30-£50+/user/month
FAQs – PBX telephone systems What does PBX stand for?
PBX stands for Private Branch Exchange and it is a private phone system used within a business.
Is PBX the same as VoIP?
No. PBX refers to how calls are managed internally. VoIP refers to how calls are transmitted over the internet and Cloud PBX systems usually use VoIP technology.
Do I still need a PBX in 2026?
Most UK SMEs no longer need a traditional PBX and Cloud PBX or hosted VoIP systems are more flexible and cost-effective.
What replaced ISDN PBX lines in the UK?
ISDN has been retired in the UK. Businesses now use SIP trunking or Cloud PBX instead.
Can I keep my existing phones with a Cloud PBX?
Often yes. Many Cloud PBX platforms support existing IP handsets or softphones.
Is Cloud PBX secure?
Yes. Reputable providers use encrypted calls, secure data centres and redundancy.
Which is cheaper: PBX or Cloud PBX?
Cloud PBX is usually cheaper overall due to lower upfront costs and inclusive maintenance.
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PBX Telephone Systems – related guides: Hi, I’m Ally Cox , a senior copywriter and blogger at CompareYourBusinessCosts.co.uk, the UK’s trusted platform for comparing business services.over a decade of experience in the B2B sector, I specialise in simplifying complex topics like leased lines, VoIP, business energy, HR and payroll solutions, accounting software, and EPOS systems .HR, copywriting, and business operations- from clocking-in systems to card machines and office technology .informed, confident decisions when choosing products and services that improve efficiency and save money.
