Stimulus package: Homeowner perks

• How 8 homeowners saved $12,275 on energy

These audits, which are sometimes offered free by a local utility, provide a detailed report of the energy efficiency of a house. The auditor locates leaks, checks ductwork and insulation, measures emissions such as carbon monoxide, and checks the efficiency of the lighting system. Some states credential contractors to provide audits, which can cost between $200 and $500. That fee is sometimes reduced if the contractor is employed to implement the upgrades.

It's money well spent, says Jason Hartke of the Green Building Council. Hartke says it's vital to discover leaks and seal them before moving on to other energy-saving investments. "There's a critical path to follow. Otherwise, you could try to do something sophisticated that won't get you the savings you want."

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