If you are without power, chances are Oncor knows about it due to the order for rolling blackouts from ERCOT(Electric Reliability Council of Texas). However, there are some outages that are not related to the rolling blackouts that need to be reported.
To report your outage to ONCOR, call 888-313-4747.
Click here to see a map of outages, check an outage status, get status alerts and more:
https://stormcenter.oncor.com/external/default.html/