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.
Typical over the range microwave under 30â kitchen cabinet might have an actual width 29 1/2â, 29 3/4â, 29 7/8â, 29 15/16â or precise 30â. Typical dimensions over the counter microwave 24â x 14â x 16â (width/height/depth) and 1.5 cubic feet capacity. Before ordering custom kitchen cabinets it is better to buy or at least know particular build-in microwave specifications and require opening.