Is it obligatory to fulfill a vow to slaughter a camel after my neighbor connects electricity to my house, or should I wait for the electricity company to connect it?

You are not obligated to do anything, because the vow is either originally not binding or it is binding but what you conditioned it upon, namely the installation of the electricity meter by the company in your house, has not yet occurred. A vow is only binding if it is an act of worship. Merely slaughtering an animal is not an act of worship, unless your intention was to give the slaughtered animal in charity to the poor. Embarking on a conditional vow is disliked, and it becomes obligatory to fulfill it when the condition it was tied to occurs. However, nothing is binding if the condition it was tied to does not occur.