What is a channel, exactly?

One simultaneous call. A 10-channel trunk allows 10 conversations at once regardless of how many phone numbers or users sit behind it. Sizing is covered in SIP trunk cost per channel .

Are inbound and outbound minutes priced the same on metered trunks?

Often not: providers price inbound and outbound legs separately, and toll-free inbound is billed to you at its own rate. Compare both legs against your traffic mix, which for most offices is 40–60% inbound.

Why do providers push per-channel?

Predictable revenue and capacity planning for them; for customers with steady high utilization it is genuinely the better deal. The push only hurts when your utilization is low — channels rented for a peak that happens twice a year.

VoIP Costs

SIP Trunk Pricing Models Compared

By the VoIP Cost Guide Editorial Team | Last updated: October 2026

If you keep a PBX (on-premise or virtual), you buy connectivity by the SIP trunk — and trunks are sold three different ways that produce wildly different bills for identical call volumes. Choosing the wrong model is the most common trunk mistake: businesses buy unlimited channels for a metered workload, or metered trunks for a call center, and overpay by half.

This guide prices all three models with the same worked workload so you can map your own call detail records onto the right one.

The three models

Model	How you pay (published ranges)	Economics
Per-channel (unmetered-ish)	$10–$25 per channel/month, domestic minutes often bundled or cheap	You rent simultaneous-call capacity, like legacy PRI channels
Metered	Low base per trunk/DID + $0.005–$0.02 per minute domestic	You pay for actual talk time; capacity (concurrent calls) often generous
Unlimited per-user bundles	Trunk features folded into per-seat hosted pricing	Effectively the hosted model — see the pricing guide

One workload, three bills

Take a 30-person office making/receiving 18,000 domestic minutes a month with a busy-hour peak of 9 simultaneous calls. Per-channel: 10 channels (peak + headroom) at a $18 sample rate = $180/month flat. Metered: 18,000 minutes at a $0.012 sample rate = $216/month plus a small trunk fee — and a quiet month costs less, a brutal month more. The crossover: at this provider pair, metered wins below ~15,000 minutes and per-channel wins above it. Move the workload to 40,000 minutes (a small call center) and metered hits $480 while channels stay near-flat — the ranking inverts. There is no universally cheaper model, only a cheaper model for your traffic shape: minutes per busy-hour channel is the ratio that decides.

Choose with your own traffic

Pull 2–3 months of call detail records from your current system or provider: total minutes and, crucially, the busiest hour's concurrent calls.
Convert busy-hour concurrency to channels with headroom: peak simultaneous calls + 20–30% (or use the channel-sizing guide linked below).
Price all three models at your real minutes and channels using each candidate provider's published rates.
Stress-test: re-price at +50% minutes (a campaign, a bad month, a new location). Metered bills spike linearly; channel bills stay flat until you outgrow capacity.
Check the fine print per model: burstable channels, minimum commitments, toll-free and international rates, and fraud caps — trunk fraud losses land on the customer in most contracts.

Frequently asked questions

What is a channel, exactly?: One simultaneous call. A 10-channel trunk allows 10 conversations at once regardless of how many phone numbers or users sit behind it. Sizing is covered in SIP trunk cost per channel.
Are inbound and outbound minutes priced the same on metered trunks?: Often not: providers price inbound and outbound legs separately, and toll-free inbound is billed to you at its own rate. Compare both legs against your traffic mix, which for most offices is 40–60% inbound.
Why do providers push per-channel?: Predictable revenue and capacity planning for them; for customers with steady high utilization it is genuinely the better deal. The push only hurts when your utilization is low — channels rented for a peak that happens twice a year.

Sources and further reading

RFC 3261 — SIP: Session Initiation Protocol (IETF)

Related guides

Disclaimer: This guide is educational information based on published VoIP standards and professional practice, not engineering advice for your specific system. VoIP pricing, taxes and fees change and vary by provider and location — verify current figures with providers before purchasing. If your phone system supports emergency calling, work with your provider or a qualified VoIP engineer for changes that affect E911.