I think It's an unreasonable question, because not only bitcoin trade will be affected, but all things powered by electricity will also disappear. Imagine life without energy, surely you will struggle everyday life by knowing that we are already living in this comfortable world because of gadgets or objects that use electricity. If it's gone then it's messed up.
You will not really bother or to troubleshoot these things first when there is a power outage surely you will find to secure your first family, loved ones about how to live without electricity rather than thinking about how you will be able to trade with bitcoin.