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 Electrical Basics. An inverter is part of a 12-volt DC system. For practical purposes, it takes 11 amps of DC power to successfully run a 1-amp AC powered device. If you have a 5-amp window air conditioner, you will need 55 amps of DC power to run the unit continuously.However, all electrical appliances have a starting surge that gets the motor running.harging. In most cases, storage batteries will be used as the power source to run the air conditioner. These batteries will need to be charged on a regular basis. Alternate forms of sustainable power are almost always used to charge the batteries, including solar panels and windmills, among others.