Fitting 16A hardwired oven to 32A cooker circuit

[Other_Tucker]

If your microwave is rated at 1000 watts it uses 1 kilowatt (kW) per hour

The 1000W refers to the actual power emitted by the magnetron in the form of microwaves for heating into the chamber. That is the energy output not the power consumption.

A 1000W microwave probably uses 1400W when running, likewise one drawing 1000W is maybe an 800W microwave. Otherwise the 900W written on my one could be any value of heating, based on its efficiency, and all food packet instructions are meaningless