TL;DR:
- Traditional VoIP pricing charges you per seat, whether used or not.
- 3CX Phone System bills for simultaneous calls, aligning cost with actual usage.
- A real-world comparison against Zoom Phone in the education sector shows 3CX can save six figures over three years.
- IT managers should reassess their VoIP provider’s model and consider switching to usage-based billing.
What is the “per-extension” billing model and why it persists
Per-extension billing is a relic from the office PBX era. Back when every desk had a phone, this model made sense: one person, one line, one cost. But in today’s hybrid world of hot-desking, mobile apps, and occasional phone use, the model is outdated. You’re often paying for dormant extensions, essentially renting desks no one sits at.
Unfortunately, many cloud VoIP providers have simply ported this model into their systems, charging by user or extension, regardless of how frequently that user makes or receives calls.
How simultaneous-call licensing works (and why it’s superior)
Modern systems like 3CX flip the script. Instead of billing by the number of extensions, they charge based on simultaneous calls (SC). An SC license covers the maximum number of calls happening at once: internal or external.
This means you can have unlimited users configured in your phone system, as long as your number of live calls doesn’t exceed your SC license. It’s like having a Netflix account that only charges you for how many people are watching at the same time, not how many profiles you have.
Key benefits:
- Costs scale with usage, not user count.
- Ideal for hot-desking, remote staff, and part-time users.
- Easy to add extensions without increasing licensing costs.
Why per-extension billing is still costing schools (and how)
Let’s say your school has 55 in-office staff and 175 nomadic users (substitutes, part-timers, administrators). Under per-extension billing, you’re paying for all 230 users whether they make one call or none.
This inflates your telecom budget with:
- Idle seat licenses
- Overhead from over-provisioning “just in case”
- Inefficiencies from underused capacity
In contrast, simultaneous-call models let you accommodate all 230 users while only paying for what’s realistically needed – say 32 or 48 concurrent calls at peak.
Comparison: 3CX vs Zoom Phone (education sector pricing)
A real-world breakdown of VoIP costs for an educational institution:
| Scenario | Users / Extensions | Simultaneous Calls Needed | Platform | Approx Monthly Cost | 3-Yr Total Cost |
|---|---|---|---|---|---|
| Zoom Option 1 – All teachers hot-desk | 230 | N/A (seat-based) | Zoom Phone | $5,476.80 | $197,164.80 |
| Zoom Option 2 – Metered phone systems | 230 | N/A (seat-based) | Zoom Phone | $3,473.05 | $125,029.80 |
| 3CX Option 1 – 32 SC | Unlimited | 32 | 3CX Phone System | $606.46 | $30,558.06 |
| 3CX Option 2 – 48 SC | Unlimited | 48 | 3CX Phone System | $878.46 | $46,919.76 |
Insight: 3CX offers the same capabilities, hot-desking, and DID support at a fraction of the cost. The difference? You’re not paying for empty desks.
Choosing the right model for your organisation: key questions
Ask yourself:
- What is your actual peak simultaneous call volume?
- How many of your extensions are idle 80% of the time?
- Do you support mobile, hybrid, or occasional-use staff?
- Are you being charged per user, per extension, or per feature?
- How scalable is your current solution if you double headcount tomorrow?
This simple audit can uncover tens of thousands of dollars in savings.
Mistakes to avoid when switching to usage-based pricing
- Under-sizing your SC license: Too few channels = blocked calls.
- Ignoring internal call volume: Internal calls count toward SC limits in 3CX.
- Comparing apples to oranges: Not all VoIP platforms offer equivalent features (e.g., call queues, IVR, softphone apps).
- Forgetting DIDs, SIP trunk, and hosting costs: Factor in the full system cost.
- Skipping the usage audit: Historical call logs are your best sizing guide.
Action plan for IT Managers
- Take a look at the other benefits of the 3CX phone system – not just per-extension billing.
- Pull historical call logs: what’s your peak simultaneous call volume?
- Inventory your extensions: who actually uses voice?
- Estimate need vs actual usage: what’s over-provisioned?
- Model 3CX vs your current platform using SC licensing.
- Get a quote: Fidalia 3CX Pricing
- Plan a migration strategy with Fidalia’s voice experts
Modern telecom should work like a utility – you pay for what you use. If your current provider is still charging per extension, it’s time to ask: how many empty desks are you funding?
For more on how 3CX can align your costs with reality, explore the Fidalia 3CX System.
Frequently Asked Questions about Usage-Based Billing for VoIP
What is per-extension VoIP billing?
Per-extension billing charges organizations based on the number of users or phone extensions, regardless of actual call volume or usage. That phone that never gets used? You pay monthly for that with per-extension VoIP Billing.
How does 3CX’s simultaneous call licensing work?
3CX licenses are based on the number of concurrent calls, allowing unlimited users and extensions while only charging for peak usage.