The hosted PBX vs SIP trunking decision comes down to one question: do you want someone else to run your phone system, or do you want to run it yourself? Neither answer is universally right. A 20-person accounting firm should not be managing Asterisk. A 200-agent call center should not be paying per-user hosted PBX fees and accepting the feature limitations that come with someone else controlling the infrastructure.
This guide explains both models, their real costs, and which operations fit each one. SIPNEX provides both SIP trunking for self-managed phone systems and hosted PBX for businesses that want carrier-managed voice. We sell both, so we have no incentive to push you toward the wrong one.
What hosted PBX is
A hosted PBX (also called cloud PBX or UCaaS) is a phone system run entirely by a provider in the cloud. You do not own, manage, or maintain any phone system hardware or software. The provider handles the PBX logic (call routing, IVR, voicemail, extensions, ring groups), the PSTN connectivity (SIP trunking to the telephone network), the phone numbers (DID provisioning and management), and the user interface (web portal, phone apps, admin console).
UCaaS-style hosted PBX commonly bills per user per month, often somewhere around $20 to $45 depending on the provider, the feature tier, and whether you pay annually. Some providers, SIPNEX included, bill per extension plus per-minute calling instead, so check which model a quote uses. Your employees use softphone apps, web phones, or SIP-compatible desk phones that register to the provider’s cloud PBX. The provider handles all maintenance, updates, failover, and scaling.
Advantages: zero infrastructure to manage, predictable per-user pricing, fast deployment (hours, not days), automatic updates and feature additions, built-in redundancy (the provider handles failover), and no need for in-house telecom expertise.
Disadvantages: limited customization (you get the features the provider offers, in the configuration options they allow), per-user pricing that becomes expensive at scale, no control over trunk-level settings (codec, DTMF mode, CID management), vendor lock-in (your call routing, IVR menus, and voicemail are in the provider’s proprietary system), and feature limitations for call center use cases (most hosted PBX platforms are not designed for predictive dialing).
What SIP trunking is
SIP trunking provides the PSTN connectivity only — the pipe between your phone system and the telephone network. You own and manage the phone system itself: your PBX (Asterisk, FreePBX, Cisco, Avaya, VICIdial), your call routing logic, your IVR, your voicemail, your recording infrastructure. The SIP trunk delivers dial tone, phone numbers, and carrier-level features (STIR/SHAKEN attestation, CNAM, failover routing). Everything above the trunk is your responsibility.
You pay per minute for calls and per month for phone numbers. On SIPNEX there is no per-user fee, no per-channel fee, and no platform fee; some carriers sell per-channel plans instead. Your PBX connects to the carrier via SIP registration or IP authentication, and the carrier handles the PSTN interconnection.
Advantages: total control over your phone system configuration, per-minute pricing that scales with usage rather than headcount, unlimited customization (any feature your PBX supports is available), less vendor lock-in (your PBX configuration stays yours; changing carriers means a new trunk configuration plus porting your numbers, updating CNAM, and re-provisioning E911 addresses), carrier-level features (A-level attestation, CNAM management, high channel counts — though channels and calls-per-second are separate limits, so ask any carrier for both), and purpose-built support for call center operations.
Disadvantages: requires in-house or contracted telecom expertise, you are responsible for PBX maintenance and updates, you manage your own failover and redundancy, and initial setup is more complex than hosted PBX.
The cost comparison at different scales
The three scenarios below are illustrative, not quotes. They assume a $30 hosted seat ($75 for a contact-center seat), a self-managed PBX on a cloud VM, per-minute rates from the bands on SIPNEX’s pricing page, and DIDs at about $1 per number per month. Your own numbers will differ.
10 users, light calling (general office).
Hosted PBX: 10 × $30/month = $300/month. Simple, predictable, calling usually bundled.
SIP trunking: PBX server (cloud VM $50/month) + trunk usage ($30/month, roughly 1,000 outbound minutes at the $0.025–$0.030 Starter band) + DIDs ($10/month) = ~$90/month. Cheaper, but you need someone to manage the PBX.
At this scale, hosted PBX wins on simplicity. The cost savings of SIP trunking do not justify the management overhead for a small office.
50 users, moderate calling (growing business).
Hosted PBX: 50 × $30/month = $1,500/month.
SIP trunking: PBX server ($100/month) + trunk usage ($200/month, roughly 7,000 outbound minutes at the Starter band) + DIDs ($50/month) = ~$350/month.
At this scale, the cost gap is significant — $1,150/month, or $13,800/year. If you have IT staff who can manage a PBX (or you use a managed Asterisk service), SIP trunking starts making financial sense.
100 agents, predictive dialing (call center). Hosted PBX: most hosted PBX platforms do not support predictive dialing at all. Contact-center seats, where offered, are commonly priced well above a standard seat. At the assumed $75: 100 agents × $75/month = $7,500/month. SIP trunking with VICIdial: dialer servers (assumed ~$200/month; a floor this size often runs as a multi-server cluster, which costs more) + 500,000 minutes at the published $0.012–$0.018 Scale band ($6,000–$9,000/month at SIPNEX wholesale rates) + DIDs ($300/month) = ~$6,500–$9,500/month.
The published band is a ceiling; clean traffic profiles are quoted below it against actual CDRs. Even so, at list rates the two models land in the same range here, so cost alone does not settle it. Capability does. Predictive dialing needs high concurrent channel counts and the calls-per-second (CPS) headroom to fill them, precise codec control, AMD tuning, and carrier-level CID management. These are SIP trunking capabilities that hosted PBX platforms do not expose.
When to choose hosted PBX
Choose hosted PBX if: your team is under 50 people and does not include a telecom or IT specialist, you need a phone system running within hours not days, your calling is primarily inbound or light outbound (customer service, reception, general business), you want predictable per-user billing with no usage surprises, you do not need predictive dialing or advanced call center features, and your priority is simplicity over cost optimization.
SIPNEX offers hosted PBX for businesses in this category. You get the carrier-grade quality (A-level attestation, CNAM, carrier support) without needing to manage infrastructure.
When to choose SIP trunking
Choose SIP trunking if: you run a call center with 20+ agents, you use predictive dialing on a platform that runs on your own trunks (VICIdial and other Asterisk-based dialers, or contact-center platforms with a bring-your-own-carrier option), you need high concurrent channel counts and the CPS to fill them, you generate 50,000+ minutes per month and cost matters, you need carrier-level control (attestation, CID management, codec selection, failover), you have technical staff or a managed PBX provider, or you need customization that hosted PBX platforms cannot provide.
Can you run both?
Yes, and many operations do. The office team (sales managers, HR, accounting, reception) uses hosted PBX for everyday communication — desk phones, voicemail, video meetings. The call center floor uses VICIdial on SIPNEX SIP trunks for outbound campaigns — predictive dialing, CID rotation, carrier-level attestation. The two systems do not need to be on the same platform. Different tools for different jobs.
Frequently asked questions
Can I use SIP trunking for a small business?
Yes, but it may not be worth the management overhead for very small operations. SIP trunking requires a PBX (hardware or software) that you manage — configure extensions, set up voicemail, maintain updates, handle troubleshooting. For a 5-person office, a hosted PBX at a typical $30/user/month ($150 total) is simpler, and the cost difference vs SIP trunking does not justify the management effort. For a 50-person business, the math can change — in the illustrative scenario above, $1,500/month for hosted PBX vs roughly $350/month for SIP trunking makes the management overhead worthwhile.
Do I need SIP trunking for a call center?
For serious outbound call center operations — particularly those using predictive dialers — yes. Hosted PBX platforms are designed for general business communication, not high-volume outbound dialing. They typically lack predictive dialing, high channel and CPS capacity, carrier-level CID management, and the codec control that dialer operations require. SIP trunking connected to purpose-built dialer software (VICIdial, Asterisk-based systems, or commercial contact center platforms) is the standard architecture for outbound call centers. At list rates the costs can land close together, so capability is usually the deciding factor.
Can I move from hosted PBX to SIP trunking later?
Yes. The transition involves setting up your own PBX (or migrating to a self-hosted solution), configuring a SIP trunk with your new carrier, and porting your phone numbers from the hosted PBX provider to the SIP carrier. The number port follows the standard LNP process; SIPNEX quotes 7–14 business days for typical ports, depending on the losing carrier. Update E911 addresses and CNAM as part of the move.
The PBX setup complexity depends on which system you choose — FreePBX and VICIdial have active communities with setup documentation. A common path is: start with hosted PBX when the business is small, migrate to SIP trunking when the operation grows to a scale where cost savings and control justify the management investment.
SIPNEX sells both models, and outbound calls on either are signed with A-level attestation. If you are unsure which fits, talk to us about your team size and call volume.
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