A wall heater for a 100-square-foot room may fall around 600 to 1,000 watts depending on insulation, climate, ceiling height, windows, and other heat sources. Many residential models designed for rooms around this size are rated between 750W and 1000W. Always verify the manufacturer's room-coverage recommendation.
A 1,000W wall heater can be appropriate for many 100 sq.ft. rooms, but actual performance depends on the room's heat loss and the manufacturer's rating. Poor insulation, large windows, high ceilings, or colder climates may require additional heating capacity.