Ask your electricity retailer or POCO for an exact final reading of the old meter.
If there was an under estimation done over the last year there might be a correct catch up reading hence a very high bill.
Was the old meter a clockdial or cyclo type ?
Also a misreading is a possibility when the meter was taken off may cause the high final reading before the meter got changed over.
A 10,000 unit reading error is a lot of money.
As said above check for an illigal tap into your supply.
Put a checkmeter in series with your kWh meter.
200 kWh a day is an enormous amount off power, have you done a check with a clip on ammeter on your supply?
200 / 24hrs = 8.333 kW load per hour.
8333 / 110 volts = 75.7 Amps total.
In case of a 2 phase supply add the readings up and see how far you are off.
Ferraris disc meters in general are very reliable long term. The few times they may go fast is only when exposed to a lightning strike which can destroy the flux of the brake magnet. But you certainly would have damage to your electrical appliances too.
Electronic meters do have faults too when capacitors become faulty on the internal circuitboards.
Isolate circuits at you mcb panel one at the time while checking the meter at the same time and see which one causes the biggest drop in usage, (flashing LED)
If it is your HVAC, check the load on the circuit concerned (amps) and get the serviceman in or sort it out yourself.
