SIP Trunking vs POTS Lines: Costs, Reliability, and When to Switch

If your business still runs on copper phone lines, you should know the clock is ticking. The big carriers are shutting down their copper networks, and the FCC just made it easier for them to move fast. In March 2026, the FCC voted to drop the long federal approval process carriers used to need before retiring copper — now they can pull the plug with as little as 90 days’ notice.

So what’s the alternative? For most businesses, it’s SIP trunking: phone service delivered over your internet connection instead of aging copper wires. This guide walks through the real cost difference, how reliability compares, and when it makes sense to switch — and when it doesn’t.

What Are POTS Lines?

POTS stands for “Plain Old Telephone Service.” It’s the traditional analog phone line that’s been around for over a hundred years — one dedicated copper wire running from your building back to the phone company’s central office.

POTS lines have one big advantage: the line carries its own power, so a basic corded phone keeps working during a power outage. That’s why elevators, fire alarms, fax machines, and security panels have run on POTS for decades.

The problem is that the copper network is going away. AT&T says it plans to stop providing copper-based service across most of its footprint by the end of 2029. And right here in New York, Verizon filed an application with the FCC in September 2026 to phase out copper landline service in New York and several other states (WAMC). Staying on POTS isn’t a long-term plan anymore. It’s borrowed time.

What Is SIP Trunking?

SIP trunking (Session Initiation Protocol trunking) carries your business phone calls over the internet instead of copper wires. It connects your phone system to the public telephone network through your data connection.

In simpler terms, your calls travel over the internet rather than over a physical phone line. There’s no physical “trunk” — it’s a virtual connection, which is what makes it so flexible. For the full breakdown, see our guide: What Is SIP Trunking? A Complete Guide for Businesses.

Cost Comparison: SIP Trunking vs POTS Lines

This is where the difference is hard to ignore.

Monthly cost per line: POTS business lines typically run $40–$100+ per month, per line. Our SIP trunking plans start at $9.99 per month.

Adding a line: POTS needs a technician visit, new wiring, and lead time. SIP channels get added in minutes — no new wiring, no waiting.

Long distance: POTS long-distance is metered at per-minute rates that add up fast. SIP long-distance rates are far lower, and often bundled.

Scaling: With POTS, every new employee means another copper pair. With SIP, you add channels as you grow and drop them if you shrink.

Maintenance: Carriers are spending less and less on the copper network while repair costs keep climbing. SIP runs over your internet connection and is managed in software.

Do the math on a 20-line office: POTS can easily cost $1,000 to $2,000 a month just for dial tone. The same capacity over SIP trunking runs a fraction of that. And since SIP channels are shared — not everyone is on the phone at the same time — most businesses need fewer channels than the POTS lines they replace.

Reliability and Call Quality

POTS earned its reputation for reliability. A corded phone on a copper line works through a power outage, no questions asked. But that reputation belongs to a network the carriers are actively tearing down. Parts are getting scarce, repairs take longer, and the infrastructure keeps aging.

SIP trunking delivers HD voice quality that sounds better than an old analog call. Reliability comes down to your internet connection: with a solid business-grade connection, voice traffic prioritized on your network, and a backup connection for failover, SIP systems are extremely dependable. The one thing to plan for is power — a battery backup (UPS) keeps your phones running in an outage, the same way you’d protect any critical equipment.

Put it this way: a well-designed SIP setup with failover is more reliable than a copper network your carrier is walking away from.

Features You Actually Get

POTS gives you a dial tone. SIP trunking gives you:

• Voicemail-to-email: messages land in your inbox.
• Mobile apps: your office number follows you on your smartphone.
• Auto-attendant and call routing: calls go where they should, automatically.
• Call recording and analytics: know what’s happening on your lines.
• Video calling: built in, not bolted on.
• Easy scaling: add a user in minutes, not weeks.
• One system across locations: offices, remote workers, and branches on the same platform.

If you have remote or hybrid workers, more than one location, or plans to grow, this isn’t a close call. See more in our guide to SIP trunking benefits.

When POTS Still Makes Sense (For Now)

There are a few cases where we’d tell you to hold off:

Fire alarms and elevator phones. Life-safety systems fall under strict codes, and they need purpose-built replacements — not a standard VoIP line swapped in over a weekend. This has to be engineered right.

No reliable internet. SIP trunking needs a solid connection. If your building’s broadband is shaky, fix that first.

You haven’t gotten a retirement notice yet. No notice means you have time to plan. Just don’t mistake that for forever.

When It’s Time to Switch

• Your phone bill keeps going up while the service gets worse.
• You’re moving or expanding. Running new copper in 2026 doesn’t make sense.
• You got a copper retirement notice — or you expect one. Ninety days goes fast.
• You have remote workers or multiple offices that need to be on one system.
• You’re paying for lines you barely use — old fax lines, backup lines, seasonal capacity.

How the Switch Works

Switching is straightforward when it’s planned properly:

1. Audit. We look at every line you have and what it actually does — voice, fax, alarm, elevator.

2. Design. SIP channels, bandwidth, failover, and code-compliant replacements for any life-safety lines, using industry-standard equipment from manufacturers like Avaya, Cisco, and Polycom.

3. Port your numbers. You keep your existing business numbers. We move them to the new service, timed so there’s no gap.

4. Cut over in phases. Tested step by step, so there’s little to no downtime.

One thing worth knowing: in many cases you can keep your existing phones. We can set up a preconfigured device that connects your current phone system to SIP service — no rip-and-replace required. Common questions about the process are answered in our SIP Trunking FAQs.

Frequently Asked Questions

Can I keep my business phone numbers?

Yes. We port your existing numbers to the new service, timed so there’s no gap in service.

Will SIP trunking work with my current phone system?

Often, yes. Many existing systems connect to SIP with a gateway or a preconfigured device. If yours is too old, we’ll tell you straight whether an upgrade costs less than working around it.

What about my fax machine, alarm panel, or elevator phone?

These need purpose-built, code-compliant replacements — a standard VoIP line won’t cut it. Don’t just unplug them. Talk to us first and we’ll map out the right replacement for each one.

How much internet speed do I need?

About 100 Kbps per concurrent call, with voice traffic prioritized on your network. A 20-person office usually needs just a few megabits for voice — any business-grade connection handles it.

How long does the switch take?

Most small to mid-size businesses go from assessment to cutover in two to six weeks. Number porting is usually the longest part.

Ready to Make the Switch?

POTS had a good run — over a hundred years of it. But the carriers are retiring copper, the FCC shortened the warning to as little as 90 days, and the cost gap isn’t closing. SIP trunking costs less, does more, and sounds better.

The businesses that switch now do it on their own schedule. The ones that wait do it on the carrier’s.

Top Line Communications has been selling, installing, and servicing business phone systems across the Tri-State area and the Greater Hudson Valley for over 30 years — Westchester, Putnam, Orange, Rockland, Dutchess, Fairfield, and New York City. We handle the whole migration: audit, design, number porting, and cutover, including the code-compliant replacements for alarm and elevator lines.

Contact us here for a free consultation and estimate — or call 1-866-95TOPLINE. With SIP trunking plans starting at $9.99 per month, there’s never been a cheaper time to upgrade. Top Line Communications is your connection to the future.

Learn more about our Telephony & SIP Trunking solutions.