I get this question from business owners about once a week: "If SIP trunks use the internet, and cloud phone systems use the internet... what's the actual difference?" It's a good question. Both get marketed as "phone service over the internet," which makes them sound like the same thing. They're not. Not even close. SIP trunking and hosted phone service solve the same problem two different ways, and the right one depends on your office — not on the marketing. I've been configuring Cisco phone systems for small businesses for over 20 years. This confusion costs people real money, and I want to clear it up.
What Is a SIP Trunk?
A SIP trunk is a phone line delivered over the internet instead of through a physical copper wire from the phone company. That's it. SIP stands for Session Initiation Protocol, but you don't need to care about that. What matters is this: a SIP trunk replaces the traditional phone line that connects your office to the outside world.
Think of it like this. Your phone system is the brain. It handles all the internal stuff — routing calls between desks, voicemail, auto-attendant, hold music, transfers, conference calls. The SIP trunk is just the road that connects your phone system to the rest of the world so people can call you and you can call them.
With a SIP trunk:
- You own the phone system
- The SIP trunk just carries your calls in and out
- Internal calls between phones in your office never touch the SIP trunk at all — they travel over your local network
- You choose your SIP provider, and you can switch providers without changing anything about your phone system
- Typical cost: $10–25 per month for a trunk
That last point is important. A SIP trunk is a commodity. If your SIP provider raises prices or gives you bad service, you cancel and sign up with another one tomorrow. Your phone system, your extensions, your voicemail, your auto-attendant — none of that changes.
What Is a Cloud Phone System?
A cloud phone system (also called hosted VoIP or hosted PBX) is completely different. With a cloud phone system, you don't own any of the phone system equipment. The entire phone system — the PBX, the call routing, the voicemail, the auto-attendant, everything — lives on servers in someone else's data center. RingCentral, Vonage, 8x8, Ooma, Nextiva — these are all cloud phone system providers.
You pay a monthly per-user fee for access to the system. Every phone in your office connects to the cloud provider's servers over the internet. Every call — including internal calls between two desks sitting 10 feet apart — routes through the provider's cloud infrastructure and back.
With a cloud phone system:
- The provider runs the PBX in its data center; you pay per user, per month
- All calls route through the provider's servers, even internal ones
- Call quality depends on the provider's infrastructure and your internet connection
- A provider outage affects every connected phone until it's restored
- Plans, features, and add-on pricing vary widely by provider — and that part matters more than the model (more below)
So What's Actually Different?
Here's a side-by-side breakdown that makes the differences crystal clear:
| Feature | SIP Trunking | Cloud Phone System |
|---|---|---|
| What you own | The entire phone system — PBX, phones, config | The phones (usually); the provider runs the PBX |
| What the provider controls | Only the phone line (trunk) in and out | Everything — your PBX, features, call routing, data |
| Internal calls | Stay on your local network — fast and free | Route through the provider's cloud servers |
| Monthly cost | $10–25/trunk; no per-user software fees | $16–$35+/user/month at the big providers’ published rates |
| Contracts | Month-to-month SIP service, cancel anytime | Varies — month-to-month to annual terms with auto-renewal |
| If provider has an outage | Internal calls still work — only outside calls affected | All connected phones are down until service is restored |
| If you want to leave | Switch SIP providers in minutes, keep your system | Port your numbers to the new provider; configuration moves with help |
| Call quality control | You control QoS on your own network | Dependent on provider infrastructure and internet |
The Money Part
Let's run real numbers for a 20-person office over 5 years.
RingCentral, month-to-month: 20 users x $35/month = $700/month — $42,000 over 5 years, before the add-ons for call queues ($35/mo), AI answering ($39/mo), and texting ($25/mo), per RingCentral's published pricing, August 2026.
On-premise Cisco system + SIP service: our 20 Express system is $1,275 one-time, with SIP Express Plus service from $161/month base. Over 5 years: $1,275 + ($161 x 60 months) = $10,935.
That's a savings of over $31,000 — and at the end of 5 years, you own the system.
"But Isn't On-Premise Complicated?"
This is the myth that cloud providers love to push. "On-premise is complicated. You need an IT department. You need a server room." None of that is true anymore — at least not with how we do it at VoIP PBX Express.
We pre-configure about 90% of your system before it ships. Your extensions, voicemail boxes, auto-attendant greetings, call routing rules — all set up and tested before the box leaves our shop. When it arrives at your office, you plug in the PBX, connect your phones, and you're making calls. The typical install takes under 2 hours. No IT department needed. No server room. No complicated configuration on your end.
If you can plug in a router, you can set up one of our systems. And if you need help, we're a phone call away — real engineers, not a chatbot.
Who Should Use SIP Trunking + On-Premise?
This combination is the right fit if you:
- Have a physical office location with 5 to 100 phones
- Want to control your costs and cut per-user software fees
- Want desk-to-desk calls to stay on your own network
- Want the freedom to switch SIP providers anytime without rebuilding your phone system
- Are replacing an aging phone system and want something that will last another 10+ years
- Have been burned by one of the big providers — bad support, surprise price hikes, impossible cancellation
When Hosted Is the Right Call — and Why Who Hosts It Matters
I'm not going to pretend hosted is always wrong. It genuinely wins when you want $0 upfront, no hardware on-site, multiple locations and remote staff on one system, or the fastest possible start. And if you're a 1–3 person shop, an inexpensive virtual-number plan is honestly all you need.
But here's what two decades of cleanup work has taught me: the horror stories — cancellation departments, offshore support queues, feature gating, contract traps — aren't a property of hosting. They're a property of the provider. RingCentral sells AI answering at $39/mo and call queues at $35/mo on top of the plan; Vonage requires its $39.99 tier before calls ring to a group; 8x8 won't publish a price at all (per each provider's published pricing, August 2026). Those are choices those companies made.
It's also why we built Cloud Express, our own hosted service: $15.75 per user per month with the Cisco desk phone included, Arthur Igloo AI receptionist and call analytics included, call recording and engineer-built call queues included, unlimited US/Canada calling — and a US-based Cisco engineer maintains your call flows and makes your changes for you. Month-to-month, no contracts. Plus taxes & fees, itemized.
We build owned systems and we host Cloud Express, so the recommendation isn't rigged: tell our Certified Network Specialists your head count and they'll show you the 5-year math both ways — and recommend whichever wins for your office.
One honest caveat: if your business needs native Salesforce or HubSpot-class CRM integrations, or a full video-meetings suite, the big UCaaS platforms are genuinely better at that — and I'll tell you so on the call.
Here's What It Comes Down To
SIP trunking is a phone line into a system you own. A hosted phone system is a PBX someone else runs for you. They both use the internet — the difference is where the brain lives and how you pay. Owned is the lowest 5-year cost; hosted is the lightest start. The wrong answer is overpaying a big provider for gated features either way.
If you're weighing the two, it's worth a 15-minute conversation — with someone who sells both and will show you the math on your exact head count.
Get a Custom Proposal — tell us how many phones you need, and we'll put together a system with real pricing. No contracts, no pressure.
Or call us directly: 844-486-4766. You'll talk to an actual engineer, not a sales rep.
