Power outage, excessive heat, ... unpredictables, do you refund?

[Kevin Lefeuvre]

We are experiencing heat wave right now in LA (and other areas in the state and in the country), where the A/Cs are not totally efficient. Some areas have even experienced power outage during the most part of the week-end.

How do you handle situations where the host is not responsible for the issues but at the end, the guest's experience is far from being good. 

Do you partially refund?