Does Southern Federal Power Serve My Oncor ZIP Code? Southern Federal Power offers residential electricity plans in many Texas ZIP codes served by Oncor Electric Delivery. The easiest way to check your address is to visit SouthernFederal.com, enter the ZIP code for your service address and review the plans currently available. A matching ZIP code is a useful starting point, but it does not always confirm your delivery utility. Some ZIP codes contain addresses served by more than one utility, a municipal electric company or an electric cooperative. Your complete service address provides the final confirmation. What Is the Oncor Service Area? Oncor [...]