POTS replacement cost calculator

Who this page is for

• You have a phone bill with copper lines and at least one replacement quote.
• You need monthly, annual and contract totals for an owner, a board or a budget request.
• You want to know when a one-time installation cost pays for itself.

Where to find each number

Number of lines. Count every line on the bill for the building or account. Some bills group lines under one main number, so ask the carrier for a full list of lines and service addresses.

Current monthly cost per line. Add the line-related charges on the bill and divide by the number of lines. Use your actual bill, not a price list. AT&T’s December 2025 FCC application shows why: it says the listed rate for its legacy business line averages about $1,700 per month, while most business customers pay an effective rate under $200 (AT&T filing).

Lines you can cancel. These are lines with no device attached, duplicates, or devices you no longer use. Confirm each one before you count it. The inventory steps on the property manager page show how.

Quoted monthly cost per replacement line. Take it from a written quote. Include anything billed monthly: data, phone service, monitoring and equipment rental. If the quote is per device, divide by the number of lines on that device.

For one reference point, the same AT&T filing lists its business replacement service at $99.99 per month before taxes and fees, including an AT&T-owned device. Independent providers such as Ooma and Granite do not publish prices, so you need their quotes.

One-time cost per line. Add hardware purchase, installation, and visits by your elevator or alarm contractor, then divide by the number of lines you are replacing. If the provider rents the hardware and installs for free, enter zero.

Contract length. The term in months from the quote.

How the calculator works

• Current monthly cost = lines × current cost per line.
• Lines to replace = lines minus lines you can cancel.
• New monthly cost = lines to replace × quoted cost per line.
• Monthly difference = current monthly cost minus new monthly cost.
• Total one-time cost = lines to replace × one-time cost per line.
• Break-even month = total one-time cost ÷ monthly difference, rounded up.
• Total over the contract = new monthly cost × months + total one-time cost, compared with the current monthly cost × the same months.

Annual figures are the monthly figures × 12. Cancelled lines count as pure savings because they are not replaced.

Making two quotes comparable

Quotes rarely use the same format. Before entering them, put each one on the same footing:

• Per line, not per device or per site
• Monitoring included, or added as a separate monthly cost
• Rental and purchase options compared over the same term
• The same treatment of taxes and fees on both sides
• Elevator and alarm contractor visits counted in one-time costs

The factors that move replacement prices up or down are explained in the POTS line replacement guide. How the devices themselves are built, and why port count matters, is on POTS in a box explained.

Reading the results

• A positive monthly difference means the new service costs less each month than your copper lines.
• The break-even month is when the one-time cost has been recovered by the monthly difference.
• No break-even means the new monthly cost is the same or higher. That can still be the right decision when the carrier is discontinuing the service or a life-safety line needs a supported path.
• The contract total is the number most boards ask for.

If you manage several buildings, run each building separately. Notice dates, line counts and contractor costs usually differ.

Have quotes that don’t line up, or no quotes yet? Send me your line count and bill, and I’ll compare at least two providers for you.