Shelley was a key member of a close circle of visionary poets and writers that included Lord Byron; Leigh Hunt; Thomas Love Peacock; and his own second wife, Mary Shelley, the author of Frankenstein.
If the 900 watts means the input power, then 1000 w inverter would be ok. If the microwave produces 900 w of cooking power, you will need a bit more, maybe 1200-1400 w if you don't know what the input power rating of the microwave is.
The 20.5 inches of clearance between the top of the cook top and the bottom of the microwave is more than adequate. The minimum amount of this clearance would be 14 inches (30 from the top of the cook top to the bottom of the counter above the microwave minus the 16 height of the microwave).This microwave can be installed above gas or electric ranges up to 36 wide.Since your new dual fuel range will only be 30 wide, the microwave can certainly be installed above this range using your current counter configuration.his microwave can be installed above gas or electric ranges up to 36 wide. Since your new dual fuel range will only be 30 wide, the microwave can certainly be installed above this range using your current counter configuration.