Carafes are made of plastic, are simple to use and typically come in a half-gallon size or larger. Many can fit in the door of a fridge. Filter changes are usually required after processing 40 gallons -- the equivalent of about three months of typical use.
Price range: half-gallon size, $10 to $40. Annual filter cost: $25 to $80.
Faucet-mounted filters attach to your faucet are compact and easy to install. The filter should generally be changed after processing 100 to 200 gallons -- at least every three months or so.
Price range: $15 to $40. Annual filter cost: $45 to $90.
Faucets with built-in filters have filter-change intervals as with faucet-mounted filters. (Consumer Reports found these didn't perform as well as the faucet-mount filters or most of the carafes.)
Price range: $150 to $300 for the faucet. Annual filter cost: $40 to $95.
Refrigerator filters come in two types. Built-in models are sold as a step-up feature with some refrigerators, while add-on units must be installed (often by a plumber) in the tubing that supplies water to a refrigerator. Both typically require filter changes after processing 250 to 400 gallons, or at least twice yearly.
Price range: add-on, $20 to $40. Annual filter cost for add-on, $5 to $20; built-in, $60 to $90.
Countertop filters often rely on a single filter cartridge.
Price range: $40 to $300. Annual filter cost: $10 to $125.
Under-the-sink filters use one to three filter cartridges.
Price range: $40 to $500. Annual filter cost: $10 to $200.
Whole-house systems can be as simple as an in-line single-stage filter or as elaborate as a large carbon cylinder.
Price range: $40 to $1,000. Annual cost: $100 to $175.
-- Consumer Reports