One meter per house/dwelling/flat.

If this isn't the case out there, how on earth do they have ANY idea
how
much you're using?

Velvet

We have a meter per unit. They are, however here, locked up and
cannot be
read by the tenants.

The manager has the key. Turn off the main braker in your apartment and
look at your meter. It should be stopped. If it isn't someone (probably
the apartment complex) is stealing your electricity. If your manager
won't open the meter room then ask the electric company to do so.