How Long Will It Last?

It's a corollary of Murphy's law: When you are least able to afford a major expense (or when repairmen are busiest), something big is bound to break down. That's why housing experts recommend that you save 1% of the purchase price of your home annually (or $2,000 for a $200,000 home) for maintenance and repairs.

Take Our Quiz: How Long Should It Last?

If you have a major home component that needs an expensive repair, consider replacing it—especially if it's near the end of its estimated life. Even better, take preventive action before a breakdown turns into an emergency (take our quiz to find out how much you know about the life expectancy of major household items). Also refer to the home-inspection report you obtained when you bought your home, which may offer more specific guidance.

The replacement costs cited below for six key components of your home are national averages from homewyse.com. They include the cost of mid-grade materials and labor for installation. Your actual costs will vary with the quality and energy efficiency of the materials you choose, as well as your location, the time of year, and the size and scope of the work. But you won't know what you'll really have to pay until you obtain bids—preferably three—from qualified and licensed local contractors (don't ignore those who work for home-improvement stores, such as Home Depot and Lowe's). One good sign is if the manufacturer has approved the contractor or store for the products that it installs. (For tips on finding great contractors, see Hire a Contractor Who Measures Up.)

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You will probably need a building permit and inspection to take on these projects, depending on your local regulations. A good contractor will handle that for you, as well as dispose of debris, old equipment and hazardous material (such as asbestos or refrigerant).

Note: Total cost is for a 2,000-square-foot home or to install a single unit.

Furnace/Boiler

Expected life: Boiler, 13 to 21 years; furnace, 15 to 20 years.

Total cost: Forced-air furnace, $1,693 to $2,020; split system, $1,604 to $2,290; oil boiler, $2,773 to $3,069.

It's time if: You need frequent repairs or have rising energy bills, rooms that are consistently too hot or cold, humidity problems, or excessive noise. If your furnace or boiler is more than 15 years old, an energy-efficient replacement will cut your utility bills.

Where to start: Use search tools at acca.org and phccweb.org.

Hot Water Heater

Expected life: 10 years for gas or electric; 20 years for tankless.

Total cost: $548 to $915 for energy-efficient model; $739 to $1,240 for tankless; $2,658 to $3,443 for heat-pump water heater.

It's time if: The unit is ten years old or more, leaks around the base, or works erratically.

Where to start: Use the guide at EnergyStar.gov to determine what type will work best for you and to get buying guidance. You can buy from home-improvement retailers or plumbing contractors).

Windows

Expected life: Aluminum, 15 to 20 years; vinyl, 20 to 40 years; wood, 30 or more years.

Cost per window: $348 to $469 (figure 50% to 100% more for "new-construction" windows).

It's time if: Windows are single-pane, drafty or fogged; frames are rotted; sashes are hard to open.

Where to start: Look for Energy Star–rated windows. At www.energystar.gov you can search for retailers and contractors who sell them. Look for home-improvement contractors certified by InstallationMasters.

Roof

Expected life: 20 years for asphalt shingles.

Cost per square foot: $5.43 to $7.05.

It's time if: You have cracked, curled or missing shingles and you're losing mineral granules (look in your gutters). In the attic, check the underside of the roof for stains or wet spots. Inside, you may see discolored plaster or drywall and peeling wallpaper.

Where to start: Use the search tool on the Web site of the National Roofing Contractors Association to find contractors who are members.

Electrical Service

Expected life: Copper wiring lasts a lifetime, but the service panel lasts 20 to 25 years.

Total cost: Rewire a circuit, $307 to $446; install a circuit, $316 to $521; upgrade an electrical service panel, $894 to $1,266.

It's time if: Circuit breakers often trip or fuses blow; you need extension cords or accessory plug strips because you don't have enough outlets; lights dim when appliances turn on; you find rust on the main service panel; your home lacks three-prong outlets or ground-fault circuit interrupters near wet locations.

Where to start: Get an electrical inspection from a licensed electrician ($268 to $400). To find a residential electrician, use search tools from the National Electrical Contractors Association and the Independent Electrical Contractors.

Central Air Conditioning

Expected life: 10 to 15 years.

Total cost: $2,460 to $3,245; split system (with interior and exterior components), $1,604 to $2,290.

It's time if: You need frequent repairs or have rising energy bills, rooms that are consistently too hot or cold, humidity problems, or excessive noise. If your system is more than ten years old, an energy-efficient replacement will cut your utility bills. Note: If your AC uses your furnace's blower motor, you may also have to replace the furnace for your new AC to achieve its rated energy efficiency.

Where to start: Look for equipment rated by Energy Star. Seek contractors who are certified by the Air Conditioning Contractors of America or who are members of the Plumbing-Heating-Cooling Contractors Association.