Energy Audits are designed primarily to measure the energy consumption of existing buildings and in some cases water consumption if desired. The final goal is to discover energy conservation opportunities (ECOs) or measures (ECMs) that reduce operating costs by improving energy efficiency. These ECMs can be no-cost, low-cost, or capital-intensive recommendations – some with immediate payback and others requiring up to several years for payback.

Depending on the needs of the building and the resources, goals, and limitations of the client, an audit can be tailored for any building. American Society of Heating Air Conditioning and Refrigeration Engineers defines three levels of audits, varying in depth and cost:

ASHRAE Level I – Walk-Through Assessment
This simple audit is the quickest, most basic type of audit. It involves minimal interviews with site-operating personnel, a brief review of facility utility bills and other operating data, and a walk-through of the facility to become familiar with the building operation and to identify any glaring areas of energy waste or inefficiency. This level of audit is adequate to prioritize energy-efficiency projects and to determine the need for a more detailed audit. Night walks can be especially helpful in discovering unrecognized energy uses.

ASHRAE Level II – Energy Survey and Analysis

]This audit expands on the preliminary audit described above by collecting more detailed information about facility operation and by performing a more detailed evaluation of energy conservation measures.. This type of audit will be able to identify all energy-conservation measures appropriate for the facility, given its operating parameters. A detailed financial analysis is performed for each measure based on detailed implementation cost estimates, site-specific operating cost savings, and the customer's investment criteria. Sufficient detail is provided to justify project implementation. This level will satisfy the auditing requirements of LEED for Existing Buildings.

ASHRAE Level III – Detailed Analysis of Capital-Intensive Modifications

This audit includes both the Level I and Level II assessment and analysis and is undertaken when validation is needed for the expenditure of capital funds. Emphasis is placed on the expected return on investment (ROI) and relies on a complete engineering study in order to detail technical and economical issues necessary to justify the investment related to the transformations
Energy Audits can be great preparation for building commissioning. See the entry on commissioning for details on the differences between audits and commissioning, as well as the additional benefits of commissioning.

Audits we coordinated at the Milan and Iowa Army Ammunition Plants discovered a combined potential energy savings of over $1,000,000 per year.