Size and location
The rangehood should cover your entire cooktop. 60cm and 90cm are the most common widths, 110cm, 120cm and 150cm models are available for larger cooking areas.
The location of your cooktop will also influence your choice. For example, if your cooktop is part of an island bench, a canopy rangehood will be suitable. If your cooktop sits under kitchen cabinets, an undermount model is your only option.