RCN, one of the broadband providers serving Dorchester, said Thursday it would be giving an automatic credit to customers who suffered from power outages during Tropical Storm Irene.

The credit, which will be based on the number of days customers saw a disruption in service, will be visible on bills going out this week and is expected to benefit 4,500 customers.

Hurricane Irene turned into a tropical storm before it hit the Bay State, but its high winds and heavy rain left hundreds of thousands of residents without power for days. The state's Department of Public Utilities is investigating the response of two utility companies, National Grid and NSTAR.