People in the UK can dial 105 to report a power cut from April next year.
It is expected to make it easier for customers to contact their local electricity distribution company for any safety concerns.
Regulator Ofcom approved the application by the Energy Networks Association (ENA).
Vodafone UK has been appointed the telecommunications service provider for the number.
It will deliver a service which will route customers to the right electricity network operator, wherever they are in the country, without them needing to know who their operator is.
Secretary of State for Energy and Climate Change, Amber Rudd said: “British families and businesses need to know where to turn if they find themselves without power during severe weather or other incidents.
“A single three-digit number cuts through the confusion and puts people in touch with the information they need, when they need it.”