If there is a Higg's field how does it sustain itself?

So if it does turn out to be the Higg's particle then if I'm understanding this correctly then this implies that there is a Higg's field that permeates the whole of space. Doesn't a field require some sort of energy source to sustain itself? Second question : fields are not necessarily uniform does this mean that mass or gravity may be different in different parts of the universe if the field is stronger or weaker?