Me I would have been trying to find accommodation with power immediately since the hotel could not give me a time.

As far as walk if the outage was out of their control and not reasonably predictable (scheduled power outage) then I do not think anything is owed.
However, If they knew beforehand because it was a scheduled thing then they owe you the difference in price and an apology for not informing you ahead of time so you could make alternate arrangement