When comparing business internet plans, the SLA, service level agreement, is often reduced to a single figure in the brochure: 99%, 99.5%, 99.9%. The figures sound similar. The difference in lost working hours is not.

The SLA is the part of the contract that sets out what the provider promises, how it is measured, and what happens when the promise is broken. Reading it before signing is far easier than arguing about it after an outage.

Reading the availability figure

Availability states what share of the time the service is promised to run. Translated into allowed downtime in a 30-day month:

  • 99%: about 7 hours 12 minutes
  • 99.5%: about 3 hours 36 minutes
  • 99.9%: about 43 minutes

Check the measurement period. 99.5% per year allows a single 40-hour outage without breach, while 99.5% per month does not.

What doesn't count

The most important part of an SLA is often the exclusions list. Commonly left out of the calculation:

  • Announced scheduled maintenance, check how long, how often, and at what hours it may happen.
  • Outages due to force majeure such as natural disasters.
  • Faults on the customer side: building power, customer-owned equipment, in-building cabling.
  • Outages the customer did not report.

That last one is often missed. In many contracts, downtime only starts counting when the customer opens a ticket. A two-hour outage overnight reported in the morning may be recorded as much shorter.

Response time and restoration time

These two figures differ and matter as much as availability.

  • Response time: how long until the provider acknowledges a report. Acknowledging is not fixing.
  • Restoration time: how long until service returns. Check whether this is a binding promise or merely a target.

Also note support hours. 24-hour fault support differs from office-hours support, especially for businesses open at night or at weekends.

Compensation

Compensation is almost always a bill credit: a percentage of the monthly fee per level of breach, with a cap, often no more than one month's fee. It usually has to be claimed, within a set time after the outage.

So an SLA is not business insurance. An online shop that loses a day of sales will not receive that day's sales back. An SLA's value lies in the discipline it imposes on the provider, not the money that comes back.

Questions before signing

  • Is it measured per month or per year?
  • What are the exclusions, and how much scheduled maintenance is allowed?
  • When does downtime start counting?
  • What restoration time is promised, and is it binding?
  • How is compensation claimed, and by when?
  • What are the exit terms if breaches keep recurring?

That last point is often the most valuable. The right to end the contract without penalty after repeated breaches gives you a real choice. Contract termination in general is covered in the guide to cancelling a subscription and contract penalties.

Translate percentages into hours, read the exclusions, separate response time from restoration time, and do not treat compensation as a replacement for losses. If the internet truly must not go down, a higher SLA is rarely enough, what you need is a backup connection from a different provider.

Frequently asked questions

How long can the internet be down under a 99.5% SLA?

About 3.6 hours a month, or roughly 43 hours a year. At 99.9%, about 43 minutes a month. Check whether the figure is measured monthly or yearly, because the results differ when one long outage happens.

Do home internet plans have an SLA?

Usually not in the form of a guaranteed availability figure with compensation. Home plans are generally best effort. Written SLAs are more common on business and dedicated plans.

Is SLA compensation paid in cash?

Rarely. Most common is a credit on the next bill, calculated as a percentage of the monthly fee with a cap. Compensation almost never covers the business losses an outage causes.