An SLA, Service Level Agreement, is the part of your contract that spells out what your provider is actually promising, and what happens if they don't deliver it. Most businesses sign one without reading it closely, then discover what it actually says the first time something goes wrong.
What an SLA actually covers
- Uptime guarantee, usually expressed as a percentage (99.9%, 99.99%) representing how much of the time the service is guaranteed to be available.
- Response time, how quickly the provider commits to acknowledging a reported issue.
- Resolution time, how quickly they commit to actually fixing it, which is a different, often much more generous, number.
- Remedies, what you actually get if they miss these commitments. Almost always a bill credit, calculated on a formula that's easy to miss in the fine print.
The number that matters more than it sounds
An SLA uptime percentage is the share of time the carrier promises the service will be available, so the remainder is downtime the carrier can have without breaking the contract. 99.9% uptime sounds close enough to 100% not to matter. In practice, it allows about 43 minutes of downtime every month, or about 8.8 hours a year.
| SLA uptime | Allowed downtime per 30-day month | Allowed downtime per year |
|---|---|---|
| 99% | 7.2 hours | 3.65 days |
| 99.5% | 3.6 hours | 1.83 days |
| 99.9% | 43.2 minutes | 8.76 hours |
| 99.95% | 21.6 minutes | 4.38 hours |
| 99.99% | 4.3 minutes | 52.6 minutes |
The gap between 99.9% and 99.99%, nearly nine hours a year versus under one, is enormous if your business genuinely can't afford outages, and irrelevant if it can. Also check how the SLA measures it: many carriers calculate uptime per month and exclude scheduled maintenance, so the downtime you actually experience can be longer than the table suggests without breaking the contract. To put a dollar figure on what those hours would cost you, use the downtime cost calculator.
Where SLAs quietly disappoint people
The remedy for a missed SLA is almost always a service credit, a partial refund on that month's bill, not compensation for whatever the outage actually cost your business. If an hour of downtime costs you real revenue, a prorated credit on your internet bill doesn't come close to covering it. This is exactly why the backup-internet decision matters more than the SLA percentage for some businesses, and why a connectivity review scores redundancy separately from cost.
Questions worth asking before you sign
- What's the actual uptime percentage, in writing, not the number a salesperson says out loud?
- How is downtime measured, and who's tracking it, them, or do you have to prove it yourself?
- What's the credit formula, and have you actually calculated what it would be worth in a real outage?
- Does the SLA cover the whole path to your building, or just their network, meaning does it protect you from problems outside their direct control?
The honest takeaway
An SLA is worth reading closely, but it's not a substitute for reliability, it's a description of what happens after reliability already failed. If your business genuinely can't tolerate downtime, the SLA percentage matters less than whether you have real redundancy in place.
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