VoIP Costs
What Replacing a PBX Costs
An aging PBX announces its replacement the way old cars do: a part that is no longer made, a vendor who no longer answers, a feature the business suddenly needs. Replacing it is a project, not a purchase — and the difference between a calm project and an emergency is whether the budget covered the whole system: network, phones, call flows, people.
This guide builds the full project budget for a 25-user replacement in both directions — to hosted VoIP and to a new on-premise/virtual PBX — with a realistic six-week timeline.
Project budget (25 users, illustrative)
| Element | To hosted VoIP | To new on-prem/virtual PBX |
|---|---|---|
| Platform | $0 up-front; $809/mo (our 25-user budget) | Appliance/VM + licenses ≈ $6,500 one-time; trunks $180/mo |
| Phones (25 + conf + DECT) | $3,750 | $3,750 (same endpoints either way) |
| Network (PoE, cabling fixes) | $800 | $800 |
| Implementation & call flows | $900 (often part-included) | $2,500 (installer project) |
| Porting & overlap | $1,200 | $1,200 |
| Training & comms | Internal time + provider onboarding | Internal time + installer training |
| Disposal / recycling of old PBX | $0–$300 | $0–$300 |
| Project one-time total | ≈ $6,650 | ≈ $14,050 |
A six-week timeline that works
Weeks 1–2: discovery and design — inventory every line, number, call flow and integration (alarm lines, fax, door phones and elevator lines are the classic forgotten endpoints); finalize design and order hardware. Week 3: network readiness — PoE, VLAN/QoS policy, circuit checks; remediate before phones arrive. Week 4: build in parallel — configure the new system on temporary numbers, record greetings, desk-drop phones after hours. Week 5: pilot with 3–5 users on real calls; fix call flows; submit porting with FOC in week 6. Week 6: port and cut over early in the week, floor-walk support for two days, keep the old PBX powered (not connected) for a fortnight as a reference, then decommission and dispose of it responsibly — it contains configuration and possibly voicemail data worth wiping.
Scope the project before pricing it
- Inventory everything connected to the old PBX — including fax, alarms, door entry, elevator and modem lines; each needs a deliberate destination (ATA, replacement service, or decommission).
- Document call flows as they are (not as designed a decade ago): who answers, overflow order, after-hours behavior, holiday schedules.
- Decide hosted vs on-premise with the 5-year comparison, then price both with the TCO checklist so the project budget and the operating budget are approved together.
- Assign one internal owner and one vendor-side owner; weekly 30-minute checkpoints beat daily panic.
- Define 'done': ports complete, old account closed, refresh reserve started, and the run-book (how to add a user, change a greeting) written down.
Frequently asked questions
- Can we phase the replacement department by department?
- Yes — hosted seats make phasing natural; on-premise can phase by floor/site with trunks shared during transition. Phasing costs a longer parallel-run but de-risks the cutover, and is the norm above ~50 users.
- What do we do with the old PBX hardware?
- Wipe configurations and stored voicemail, then recycle through an e-waste handler. Keep one shelf-spare handset set only if the same phones remain in service elsewhere; otherwise it is shelf clutter with a power supply.
- Our PBX still works — why replace it now?
- Because replacement on your schedule costs the project budget above, while replacement on its schedule costs that plus emergency labor, expedited hardware, and days of degraded phones. End-of-support dates, not failure, should trigger the project.