An energy audit is the first step in determining what you can do to make your home more energy efficient. A Do-It-Yourself audit will cost you nothing, and can reveal problems that, once fixed, can save you a significant amount of money over time. A Professional Audit will go into much more detail, using technologies such as blower doors and infrared cameras, and will probably uncover energy savings opportunities that you would have missed on your own.
As is the case with any services you buy, if you’re hiring a professional energy auditor, you should get itemized quotations from several contractors. Determine if they have BPI certification, nationally know accreditation from the Building Performance Institute. And of course contact their references.
Eversource (PSNH) offers free energy audits to its residential customers, and will pay up to $4000 for efficiency improvements that will reduce electric usage. (You will have to pay for any improvements that reduce fossil fuel usage.)
The Dunbarton Energy Committee has a Neighbors Warming Neighbors program that provides a mini audit that is not BPI-certified but can help you plan an DIY energy efficiency update program.