This debate should have ended in 2022. It did not, because some consultants still recommend on-premise PBX systems to justify their installation fees. Here is the honest comparison — from someone who deploys both.
The Numbers (No Spin)
50-User Deployment, 3-Year TCO
| Cost Category | On-Premise PBX | Cloud VoIP |
|---|---|---|
| Hardware (PBX + phones) | £35,000 | £7,500 (phones only) |
| Installation + cabling | £8,000 | £0 |
| SIP trunks / lines | £18,000 (3 yrs) | £0 (included) |
| Maintenance contract | £14,400 (3 yrs) | £0 (included) |
| Software licences | £9,000 (3 yrs) | £0 (included) |
| IT admin labour | £21,600 (3 yrs) | £3,600 (3 yrs) |
| Firmware updates | £4,500 (3 yrs) | £0 (automatic) |
| Disaster recovery | £12,000 | £0 (built-in) |
| 3-Year Total | £122,500 | £50,700 |
| Per user per month | £68 | £28 |
Cloud VoIP costs 59% less. And the on-premise figure does not include the opportunity cost of the IT hours spent managing the PBX.
When On-Premise Still Makes Sense (Rarely)
| Scenario | Why On-Premise | How Common |
|---|---|---|
| Zero internet reliability | Absolute need for PSTN fallback | < 2% of UK businesses |
| Military/government classified | Air-gapped network requirement | Specialised sector |
| 5,000+ seat single site | Economy of scale for hardware | < 0.1% of businesses |
| Existing 5-year PBX contract | Sunk cost, wait for contract end | Declining |
If you do not fit one of these four scenarios, on-premise PBX is the wrong choice in 2026.
The Arguments Against Cloud (Debunked)
"What if the internet goes down?"
Modern cloud VoIP handles this:
- Calls failover to mobile app on 4G/5G automatically
- Dual ISP with SD-WAN provides redundancy
- Even a basic 4G backup router keeps calls running
Meanwhile, if your on-premise PBX fails, calls stop entirely unless you have a maintenance contract with a 4-hour response SLA — and someone available at 3 AM.
"We need control over our data."
Cloud VoIP with UK data residency (which DialPhone provides) gives you:
- Recordings stored in UK data centres
- Full data export at any time
- DPA/BAA signed
- You control retention policies
With on-premise, data control means YOUR IT team is responsible for backup, encryption, access control, and disaster recovery. Most SMB IT teams do not have the expertise or time.
"Cloud is more expensive long-term."
This was true in 2015 when cloud VoIP was £40-60/user. In 2026, cloud VoIP at £24/user is cheaper than on-premise from year one — before you even factor in the hardware depreciation, maintenance, and IT labour.
The Decision Matrix
| Factor | On-Premise Score | Cloud Score |
|---|---|---|
| Upfront cost | 1/5 (£35-50K) | 5/5 (£0-8K) |
| Monthly cost | 2/5 (£55-70/user) | 5/5 (£20-30/user) |
| Scalability | 2/5 (hardware limited) | 5/5 (add users in minutes) |
| Remote work | 1/5 (VPN required) | 5/5 (built-in mobile app) |
| Disaster recovery | 2/5 (extra cost) | 5/5 (built-in geo-redundancy) |
| Maintenance burden | 1/5 (your responsibility) | 5/5 (provider handles everything) |
| Feature updates | 2/5 (manual firmware) | 5/5 (automatic, continuous) |
| Total | 11/35 | 35/35 |
Cloud wins every category except situations requiring zero internet dependency (which applies to almost nobody).
DialPhone is cloud VoIP designed for UK businesses. £24/user, everything included, month-to-month. The on-premise vs cloud debate is over. The cloud won.
