What is a call avalanche?
A call avalanche - also called a call storm, call spike or call surge - happens when a single event makes a large share of your customers ring at once. In a contact centre that normally receives a few dozen calls an hour, a widespread power cut can bring thousands in the first hour. Queues that were empty a minute ago fill faster than agents can log in.
The term is used most in energy and utilities, where storms, earthquakes and network faults cut supply to whole regions, but any organisation can face one: a bank whose app goes down, a telco with a network outage, a retailer issuing a product recall, or a government agency announcing a new scheme.
Why call avalanches break normal contact centres
Contact centres are staffed to forecast. Workforce management tools and Erlang C models plan for expected volume, plus a margin. A call avalanche sits far outside that margin, so a few things happen at once:
- Queues explode. Average speed of answer goes from seconds to an hour or more, and service level collapses.
- Callers abandon and redial. High abandonment doesn’t reduce demand - frustrated customers ring back, so the same person may count as five or ten calls.
- Phone lines saturate. Without enough capacity in the telephony layer, callers hear an engaged tone or the call drops before it ever reaches a queue.
- Urgent calls get stuck. Most callers in an outage want the same thing: what’s happening and when will it be back on. But mixed into that queue are hazard calls about fallen lines and calls from medically dependent customers. If everyone waits in one queue, the calls that matter most wait longest.
The anatomy of an outage call avalanche
In a typical storm event, call volume follows a recognisable shape. There’s a near-vertical spike in the first 30 to 60 minutes as power goes off, a long plateau of status and restoration questions while crews work, and smaller secondary spikes whenever an estimated time of restoration changes or is missed. Each new update - on the website, by SMS or in the media - can trigger its own wave.
That shape matters, because most of the volume is repetitive and informational. The same handful of questions account for the bulk of calls, which makes them well suited to automation and proactive messaging.
How organisations manage a call avalanche
The most resilient approach combines several measures rather than relying on any one:
- Deflect what you can. Proactive outage notifications, outage maps and up-to-date IVR messages answer the question before the customer has to ring.
- Answer the rest instantly. An AI voice assistant can hold thousands of simultaneous conversations, give the latest information from your outage management system and log new faults.
- Add people fast. Surge capacity from a partner with already-trained, shared agents covers calls that need a human.
- Prioritise by risk. Route safety and vulnerable-customer calls to people first, using rules agreed before the event.
- Stay up yourself. A contact centre with home-based agents across many locations keeps running even when the storm hits its own city.
The organisations that cope best plan for the avalanche before it arrives. That means agreeing scripts, escalation rules and capacity in advance rather than improvising on the night.