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.
Some manufacturers allow smaller clearances. General Electric, for example, requires that its microwaves be mounted with a minimum of 66 inches between the floor and the top of the microwave, which results in a clearance of between 13 and 16 inches from the microwave to the cooktop.he National Kitchen and Bath Association recommends that the bottom of the microwave should be no higher than 54 inches above the floor, which would allow for 18 inches of clearance between the microwave and the typical cooktop height of 36 inches.