Repairing or replacing a furnace or air conditioner

Signs it's time to call a contractor

• Age. The heat pump or air conditioner is more than 10 years old, or the furnace or boiler is more than 15.
• Repairs and bills. The equipment needs frequent repairs, and the energy bills keep rising.
• Comfort. Some rooms are too hot or too cold.
• The air. The house has humidity problems or excessive dust.
• Noise. The system is noisy.

Problems that aren't the furnace

Several of those signs can start outside the equipment. Rooms that are too hot or too cold can come from duct problems or poor insulation. Excessive dust can come from leaky ducts pulling particles in from the attic, crawl space or basement. A noisy system can mean the ducts are too small.

Before buying new equipment, have the big air leaks in the house and the ducts fixed. Sometimes they're the real cause.

What new equipment changes

New equipment alone can cut heating and cooling energy use by 20 percent or more. With insulation, air sealing and better thermostat settings added, the savings can reach about 30 percent. An ENERGY STAR furnace is 15 percent more efficient than a conventional one.

Installation matters as much as the label, because a poor installation can cut a system's efficiency by up to 30 percent.

What to ask the contractor for

When you're weighing a repair against a replacement, ask the contractor to cover:

• the safety and cost of repairing the equipment, compared with replacing it;
• the equipment options;
• the sizing calculations;
• other improvements, such as air sealing, that affect the result.

For a replacement, ask the contractor to inspect the system and the house before quoting. Ask for the new equipment to be sized from the house's size, insulation and windows. An oversized system is no better than one sized from the house. On a split-system air conditioner, a new outdoor unit without a matching new indoor unit is likely to run at low efficiency and may fail early.

An annotated example

What to do next

Write down the age of each unit, its model, its maintenance history and the rooms that are uncomfortable. Then ask for written, itemized estimates, and compare the cost, energy efficiency and warranty of each.