Hosted VoIP vs on-premise PBX: which is right for you?

What is hosted VoIP and what is an on-premise PBX?

Both are ways of running a business phone system, but they sit in very different places. A PBX (Private Branch Exchange) is the system that connects internal extensions and routes calls in and out of your business. The question is simply where that system lives.

With hosted VoIP, the phone system lives in your provider's cloud. There is no box in your building. Your staff connect to it over the internet using a mobile app, a web softphone or an IP desk phone, and the provider runs everything behind the scenes. It is often called cloud PBX or cloud telephony. If you want a primer on the underlying technology, see what is VoIP and how does it work.

With an on-premise PBX, you buy and install the system physically on your own site. You own the hardware, it sits in a comms room or cupboard, and your business is responsible for powering it, maintaining it and upgrading it. Historically this was the only option, and many older businesses still run one. The trend, however, is firmly towards hosted, and the closure of the old PSTN and ISDN networks on 31 January 2027 is accelerating it.

How do hosted VoIP and on-premise PBX compare?

The differences become obvious when you lay them out side by side. The table below compares the two on the factors that drive the decision for most businesses.

Factor	Hosted VoIP (cloud)	On-premise PBX
Upfront cost	Little or none; desk phones optional	High, often £1,000+ per user with hardware and install
Monthly cost	Predictable per-user fee, about £7 to £30	Line rental, maintenance and support contract
Maintenance	Handled by the provider in the cloud	Your responsibility (IT team or contract)
Upgrades and features	Rolled out automatically	Manual, sometimes needs new hardware
Scaling	Add or remove users in minutes	Capacity limited by hardware; engineer to expand
Remote and hybrid work	Built in; works anywhere with internet	Tied to the site; remote access needs extra setup
Control	Provider runs the platform; you manage settings	Full ownership of the equipment
Future-proofing	Already IP-based and 2027-ready	Must be on IP, or replaced before the switch-off

Read down the table and the pattern is clear. Hosted wins decisively on cost, maintenance, scaling, remote work and future-proofing. On-premise holds one genuine advantage, direct ownership and control of the hardware, which matters to a small minority of organisations.

What does each option really cost?

Cost is usually the deciding factor for a small business, and the two models work very differently. An on-premise PBX is a capital purchase: you pay a large upfront sum for the system, handsets and installation, often £1,000 or more per user once everything is included, then carry ongoing line rental, maintenance and the cost of fixing faults yourself. If the business grows, you may need to buy more hardware.

Hosted VoIP is an operating cost: a predictable per-user monthly fee, typically £7 to £30, with UK calls and updates included and no hardware to buy. There is no capital outlay and no surprise repair bills. Over a three to five year window, the total cost of ownership for most SMBs comes out well below an on-premise system, because you are not paying for hardware, maintenance and capacity you may not use. For a full breakdown by team size, see our guide to business phone system costs in the UK.

When does an on-premise PBX still make sense?

It would be unfair to say on-premise is always wrong. There are still a handful of situations where it can be the right call. A very large organisation with thousands of extensions and a dedicated telecoms team may prefer the control of running its own platform. A business with strict requirements to keep call data physically on site, perhaps for regulatory reasons, might choose on-premise for that reason. And a company that recently invested heavily in PBX hardware may want to use it up before switching, provided it can connect over IP.

These cases are the exception rather than the rule, and they are shrinking. Even organisations that once needed on-premise control are finding that modern hosted platforms meet their security, compliance and feature needs. For most UK small and medium businesses, the maintenance burden, upfront cost and lack of flexibility make on-premise hard to justify in 2026.

What does the 2027 switch-off mean for this choice?

It sharpens the decision considerably. The UK PSTN and ISDN networks, which traditional phone systems rely on, are being switched off on 31 January 2027. After that date, any phone system still connected over those old lines stops working. An on-premise PBX is not automatically affected if it already connects over IP, but a great many older systems do not, and those will need to be migrated to internet connectivity or replaced before the deadline.

Hosted VoIP sidesteps the whole problem, because it is already internet-based and ready for the switched-off world by design. There is no hardware to migrate and no last-minute scramble. For a business weighing the two options now, this is a strong reason to choose hosted: you solve the 2027 requirement and modernise your phone system in one move, on your own timetable. To plan the deadline properly, read our guide to the PSTN and ISDN switch-off in 2027, and browse the full set of guides in our Learn hub.