Most owners price a backup circuit wrong. In both directions.
They think a backup means buying their primary circuit twice. So they never buy one. And they think an outage costs "a few hours." So they never do the math. Both mistakes come from the same place. Nobody showed them the real numbers.
Let's fix that.
Price your own outage in ten minutes
Forget the enterprise stats you have seen. The $5,600-a-minute number is for a Fortune 500, not your 25-person office. Here is the math that actually applies to you.
Add three things. First, the hourly payroll of staff who can't work. Second, the revenue you can't take or bill during the outage. Third, hard costs like missed deadlines or customer credits. Then multiply by your realistic outage hours per year.
A single business circuit goes down 2 to 8 hours a year. That is normal.
Worked example. A 25-person office where half the team sits idle. Add in payments you can't run and billing you can't send. That lands around $1,800 to $3,500 per outage hour. Four hours a year is $7,200 to $14,000. That is the number to compare a backup against.
Why your SLA credit is not a backup plan
Your carrier has a service level agreement. It sounds like protection. It is not.
A typical business SLA pays one day's prorated monthly charge, capped at a slice of your bill, and only if you file inside the window. The window is often 30 days. On a $600 circuit, that is about $20 back for a day that cost you thousands.
Read three clauses before you lean on it. "Service Credit" tells you the payout. "Chronic Outage" tells you when you can leave. "Sole and Exclusive Remedy" tells you that credit is all you get. That last one is the trap.
The backup does not need to be your primary twice
Right-size the failover to the apps that stop the business. Phones. Card processing. Email. Cloud access.
Most offices run all of that on 50 to 200 Mbps. You do not need a duplicate gig.
Price it out. Coax business cable runs $80 to $200 a month. Fixed wireless on 5G or LTE runs $50 to $150. A second fiber from a different carrier runs $300 to $800. Now compare that to a duplicate 1 Gbps DIA at $900 to $1,500. You are paying for symmetry you will never use in a failover.
"Diverse path" is the question that actually matters
Two circuits from two brands can still fail together. They share a conduit, a utility pole, or the same wholesale last-mile provider. Most buyers never ask. The carrier never volunteers it.
Ask in writing: "Does this circuit enter the building through a separate entrance facility and ride a separate last-mile provider from my primary carrier?"
A second fiber often just resells the same lit building. Cable or wireless is usually the more genuinely separate path. Different plant, different failure.
The costs that aren't on the circuit quote
The circuit price is not the whole bill.
You need hardware to switch between the two lines. A dual-WAN router or SD-WAN box runs $400 to $1,500 one time, or $30 to $100 a month on a managed plan. Install fees range from $0 for cable to $1,000 or more if fiber needs construction.
Then the term. Backups often lock you in for 12 to 36 months. A 36-month backup can outlive your primary contract. That makes your next renegotiation a mess.
Three real configurations with total monthly cost
Here is what people actually buy.
- 200 Mbps fiber primary plus 5G backup: roughly $500 to $700 a month all in.
- 500 Mbps fiber plus business cable: roughly $600 to $900 a month.
- Dual fiber from two carriers: $1,100 to $1,800 a month.
Look at the backup as a percentage of your primary bill. For the first two options, it is 15 to 35 percent more. Set that against a $7,200 to $14,000 outage year. The math is not close.
How to buy it without overpaying
Ask your current carrier for a backup quote last, not first. They will quote their own product and quietly skip the diversity point.
Get the diverse-path confirmation in writing. Negotiate the backup term to match or beat your primary. Ask for an install fee waiver on a 24-month term. They have room.
Then test it. Set a quarterly failover test and put the date in your calendar the day you sign. Most people never test it. Then the backup fails the one time they need it.
Stop treating redundancy as a yes or no on buying your circuit twice. Price your own outage. Buy a smaller line on a truly separate path. Negotiate the term and the install.