The True Cost of Replacing Your Legacy PBX System

Your current phone system might still cover the basics — but for many businesses, it’s becoming clunky, unreliable, and costly to maintain. It wasn’t built for today’s remote and hybrid ways of working, and every time the topic of upgrading comes up, the same question stops you in your tracks: “How much is this actually going to cost?”

At Babble, I work with businesses every day that are upgrading from legacy PBX or SIP systems to cloud-based solutions. Some have 5 users, some have 500 — but the goal is the same: build a setup that’s flexible, resilient, and future-ready. Most upgrades are either cost-neutral or result in savings, once you factor in what you're already spending to maintain ageing tech.

By the end of this article, you’ll understand what influences migration costs to a cloud-based phone system, how those costs compare to maintaining a legacy PBX or SIP setup, and what to consider when budgeting.

-

What This Blog Covers: 

• Is a Cloud Phone System More Expensive Than What I Have Now?
• What Can Affect the Price?
• What is the cost per user for a UCaaS?
• How long will it take to switch, and when should I start planning?
• My Advice: Consider The Cost of Doing Nothing
• What’s Next?

Is a Cloud Phone System More Expensive Than What I Have Now?

Most small and medium size businesses don't switch to a cloud-based phone system - known in the industry as UCaaS - because they fear it is too expensive. Especially if you're already paying for on-prem system support, SIP lines, and occasional engineer callouts. The goal for many UCaaS (cloud phone system) migrations at Babble is to deliver a solution that falls within, or is close to, your current monthly spend. You may not even need to increase your telecom budget at all unless you’re scaling up significantly or adding advanced features.

Even then, you're gaining a more flexible and future-ready platform in return. UCaaS is priced as a monthly operational expense (OPEX), making it more predictable than the capital-heavy PBX model, where monthly maintenance costs will fluctuate.

What Can Affect the Price?

Once you understand the baseline costs, it’s helpful to know what makes some businesses pay more than others, and where you might save.

What Might Increase Your Costs:

• Connectivity upgrades: If your current broadband isn’t reliable enough to support cloud telephony, you may need to install a dedicated line or split voice and data to ensure call quality.
• Custom integrations: UCaaS works seamlessly with big-name CRMs like Salesforce, HubSpot, and Sage. But if your business uses something bespoke, custom integrations may add one-time development fees.
• Advanced requirements: Larger organisations often need custom call flows, analytics, or multi-site coordination, which can increase the complexity and implementation time.
• New hardware: If your current handsets or routers aren’t compatible, you may need to budget for replacements or rentals.
• Implementation requirements: Larger organisations may require added coordination and engineering for complex setups, typically starting around £300 and scaling with complexity. But this is always discussed in advance, and we’ll walk you through exactly what’s needed and why.

What Can Help Keep Costs Low:

• Simple requirements: If you just need to make and receive calls reliably, without complex routing or reporting, you’ll likely fall on the lower end of the pricing spectrum.
• No integration needs: Sticking with standard features avoids custom development.
• Using what you already have: If your handsets, router, and broadband are up to the task, there’s no need to invest in new kit.

Your price isn’t just about user numbers—it’s about what you need your system to do, and what you already have in place.

What is the Cost Per User for UCaaS?

Typically, prices fall somewhere between £20–£35 per user per month. But that’s only part of the picture. While most businesses focus on the monthly cost, it’s also important to consider any initial migration or setup fees, especially if your current system needs upgrades or custom configuration.

There’s no single “sticker price” for migrating to a cloud phone system, because every business starts from a different point. Your total cost will depend on your current setup, how many users you have, what equipment you already own, and whether any upgrades or integrations are needed. In smaller deployments, these setup costs may be minimal or even waived. For larger, more complex rollouts, implementation typically starts around £300 and scales with need, but this is always scoped and agreed upfront.

For example, a 5-user estate agency and a 100-user logistics firm might adopt the same cloud phone system — but they won’t pay the same per user. Larger businesses often already have high-speed broadband and benefit from economies of scale. Smaller teams may pay a bit more per user, but typically need simpler setups.

Most per-user prices include more than just a phone line. They typically cover features like voicemail-to-email, call forwarding, mobile access, and even handset rental. In many cases, training, support, and even basic implementation are bundled in. What matters most is building the right solution around your needs, not forcing you into someone else’s template.

How Long Will It Take To Switch - and When Should I Start Planning?

For businesses under 20 users, we typically complete the full switch within 3-4 weeks.

Larger, more complex deployments of 100+ users or multiple sites can take 2-3 months to plan, configure, and launch — especially if there's advanced call routing, analytics, or integrations involved.

Start budgeting and planning at least 1–2 quarters ahead, especially if:

• You want to spread upfront costs
• You’re aligning with contract end dates
• You need time to assess or upgrade connectivity and infrastructure

My Advice: Consider the Cost of Doing Nothing

It’s tempting to avoid switching just to “save the hassle.” But legacy systems carry their own risks:

• Expensive engineer callouts if hardware fails
• Replacement parts that are hard to source (and not cheap)
• Downtime risk from site-based failures
• Limited mobility—a real issue in today’s work-from-anywhere world

But what about the cost of doing nothing? Every missed call, lost sale, or delayed response adds up — not just in money, but in reputation and reliability. With UCaaS, downtime doesn’t have to take you offline — your team can stay connected from anywhere.

 What’s Next?

 If you’re still unsure whether now’s the right time to move away from your legacy system, start by asking this: What are we already spending, and what are we getting for it?

That £500/month on SIP lines, maintenance, and emergency engineer callouts might seem manageable — until you realise it adds up to £6,000 a year invested in ageing infrastructure that could fail at any moment, taking your phones and your revenue down with it. UCaaS offers a way out of that cycle. It’s about building a more resilient, flexible, and cost-predictable setup for how your team actually works today.

At Babble, we’ll help you make the switch with clarity and control. No assumptions. No one-size-fits-all packages. Just a clear plan that shows where you can save, what’s possible, and how to move forward.

You don’t have to make the leap alone. We’re here to guide the process — not pressure it.