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).
You pay per user per month — typically $20 to $45 depending on the provider and feature tier. 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. There is no per-user fee (on SIPNEX), no per-channel fee, and no platform fee. Your PBX connects to the carrier via SIP registration, and the carrier handles the PSTN interconnection.
Advantages: total control over your phone system configuration, wholesale per-minute pricing that is dramatically cheaper at scale, unlimited customization (any feature your PBX supports is available), no vendor lock-in (switch carriers by changing SIP credentials), carrier-level features (A-level attestation, CNAM management, unlimited channels), 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
10 users, light calling (general office).
Hosted PBX: 10 × $30/month = $300/month. Simple, predictable, includes everything.
SIP trunking: PBX server (cloud VM $50/month) + trunk usage ($30/month at light volume) + 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) + 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. The ones that offer “contact center” features charge $50-$100/user/month. 100 agents × $75/month = $7,500/month.
SIP trunking with VICIdial: PBX server ($200/month) + trunk usage at 500K minutes ($4,000/month at SIPNEX wholesale rates) + DIDs ($300/month) = ~$4,500/month.
At call center scale, hosted PBX is not just more expensive — it is often incapable of supporting the workload. Predictive dialing requires unlimited concurrent channels, 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 (VICIdial, Five9 on-premise, Genesys), you need unlimited concurrent channels, 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
What is the difference between hosted PBX and SIP trunking?
Hosted PBX is a complete phone system managed by a provider in the cloud — the provider handles the PBX logic, PSTN connectivity, phone numbers, and user management. You pay per user per month and get a turnkey phone system. SIP trunking provides only the PSTN connectivity — the pipe between your self-managed phone system and the telephone network. You own the PBX, manage the configuration, and pay per minute for calls. Hosted PBX is simpler but more expensive at scale and less customizable. SIP trunking is more complex but cheaper at scale and fully customizable.
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 $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 changes — $1,500/month for hosted PBX vs approximately $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, unlimited concurrent channels, 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. The per-minute pricing model is also dramatically cheaper at call center volumes than per-user hosted PBX pricing.
Can I switch 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 phone number port follows standard LNP process (7-14 business days). The PBX setup complexity depends on which system you choose — FreePBX and VICIdial have active communities with setup documentation. The most 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 provides both SIP trunking for self-managed operations and hosted PBX for businesses that want simplicity. Both come with A-level STIR/SHAKEN attestation and carrier-grade infrastructure. Talk to us about which model fits or see our rates.
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SIPNEX
FCC-licensed carrier with its own STIR/SHAKEN SP certificate. Operator-owned. SIP trunks built for operators who dial at volume.