Is UCaaS always cheaper than a PBX?

Not always. UCaaS shifts spend to predictable per-seat subscriptions and reduces hardware capital outlay. A PBX you already own may be cheaper to run for several years — until maintenance, capacity limits, or remote-work requirements force a change. Compare total cost over your planning horizon, not just the first-year invoice.

Can we keep our desk phones with UCaaS?

Often yes — many UCaaS platforms support standard SIP phones. Compatibility depends on the platform and phone models. Confirm before you buy new hardware or assume your existing fleet will work.

What happens to our phone numbers when we move to UCaaS?

Local and toll-free numbers can usually port to the new carrier or platform, but porting has lead time and documentation requirements. Start the porting conversation before you announce a go-live date to customers.

When does keeping a PBX still make sense?

When the system is stable, capacity is sufficient, your team is mostly on-site, and you have internal expertise to maintain it. PBX also remains relevant in environments with strict data-residency or integration requirements that a given cloud platform cannot meet.

Comparison

UCaaS vs PBX for business phone systems

The decision is not "cloud good, on-prem bad." It is whether your operating model, growth plans, and support capacity fit a subscription platform or a system you own and maintain on-site.

Swipe to compare

Factor	UCaaS / cloud voice	On-premises PBX
Upfront cost	Lower hardware capex; per-seat subscription	Higher hardware/licensing upfront
Remote & hybrid work	Native softphones and mobile apps	Possible but often bolted on
Scaling seats	Add licenses; watch per-seat add-ons	Limited by hardware capacity/licensing
Maintenance	Vendor handles platform updates	Your team or MSP maintains hardware
Outage profile	Depends on internet + vendor SLA	Local control; still needs WAN for remote users

When UCaaS is the better fit

Distributed teams, frequent hiring, and integrations with Microsoft Teams or CRM tools push most growing businesses toward UCaaS. You trade capex for subscription discipline — and you must read the contract for channels, recording, contact-center add-ons, and AI features that inflate the per-seat total.

When a PBX still earns its place

A well-maintained PBX with life left in the hardware can be the right answer for a single-site business with stable headcount. Replacement triggers usually appear when you need mobile-first calling, multi-site dialing, or your vendor stops supporting the platform — not because cloud is fashionable.

Questions to ask either vendor

What is included in the quoted per-seat price vs licensed add-ons?
How are 911/e911 and regulatory requirements handled in Canada?
What is the porting timeline for existing numbers?
What uptime SLA exists and how are credits claimed?
What happens at contract end — data export, number portability, equipment?

See also our UCaaS buyer's guide and voice & UCaaS procurement.