I have in the past used energy monitors to get an idea of how much power each device in a factory is using.
you could buy a couple of these and put them on each of your heating units.
they are the most likley high usage devices you have.
if they account for 90% of the usage then i am afraid you will have to turn the heating down.
if they are less than 50% of your usage then i suspect you have a problem with either billing meter or a leech drawing your electricity for there own use.
Eco-Eye Smart PC - Eco-eye electricity monitors (eco-eye.com)
there may well be a member who can install them on different circuits for you at different times if you are not confident.