There is always the possibility of the WH leaking. If it turns on while it is empty, it can create problems. Safer thing to do is to either turn the thing to pilot only mode (if it has a pilot) or shut it off, which would require relighting it (usually fairly easy if it has a standing pilot, should not be necessary if it has an ignighter). then you could turn off the water.
The utility company shouldn't care one way or the other.