may be a quick question but not necessarily a quick answer. It depends upon
1) what else may be on the circuit in your friends house,
2) if it is a 15 amp or 20 amp breaker
3) how long of an extension cord you may have to use.
4) how good you are about managing the electrical loads.
5) whether your battery charger kicks on at the same time as your fridge or your AC, etc.
we plugged into a friends house and everything seemed fine for a while and then his breaker would trip every time his freezer in his basement kicked on. turned out it was on the same circuit.