Does your kitchen already have ducting? If you already have ducting installed, this could save you a lot of time and money in installation costs. Be sure to get measurements on your venting system to make sure the new range hood's specifications match what you already have.
Do you want to install ducting or get a non-ducted range hood? You can save a lot of money by installing a non-vented range hood. However, some professional reviewers recommend a ducted system because it takes smoke, odors, etc., outside instead of recirculating them in the kitchen.
If you have an older home, where does the ductwork end? Never exhaust air or terminate ductwork into spaces between walls, crawl spaces, ceilings, attics or garages. All exhaust must be ducted to the outside. If it isn't, figure in the cost of correcting this.
What's your kitchen design? Whether you are remodeling a kitchen or building one from scratch, the location of your cooktop will determine what type of range hood you install. If the cooktop is on an island, you'll need an island-mounted range hood. Cabinets above the cooktop? Go for an under-cabinet range hood. Is the area above the cooktop clear? A wall-mounted range hood will work.
What style and color are your appliances? Make sure your new range hood comes in the style and color of your kitchen. Some manufacturers offer a variety of colors, while others focus on stainless steel.
Purchasing a range hood is a fairly straightforward deal -- you are investing in an integral part of your kitchen. You can spend less than $50 for a non-vented hood or thousands of dollars on a particular range hood model. Maintenance costs are minimal. From time to time you'll need to replace light bulbs and filters. If your range hood is made of stainless steel, you might want to purchase a cleanser or polish specifically made for stainless steel. Most manufacturers offer at least a one-year warranty on parts; some also offer warranties on labor.