During a power failure, your cordless phones will not work. But, unless the phone lines are also down, a corded phone will work. This was such a relief for us during Hurricane Wilma. The power was out for five days but we always had phone service thanks to the old-fashioned corded phone.
I have used the corded phone during several shorter power outages as well. I tape the customer service number of the power company to the phone. That way, as soon as we loose power, I am able to call the power company to report the outage and get an estimate of when power will be restored.
You may be thinking that you can just use your cell phone and that may work for a while. But let me just say (from experience) that during a crisis (such as a hurricane) the cell phone lines may be overloaded and eventually the cell phone will need to be recharged.
If you don't have a corded phone, head to the nearest thrift store where you should be able to pick one up super cheap. Or, you can still buy them at Amazon
for around $10.
If you don't want to use the corded phone on a regular basis, you can store it with your other emergency supplies (such as flashlights). When the power goes out, you'll be glad you did!