An Energy Audit according to Wikipedia is an inspection , survey and analysis of energy flows for the energy conservation in building, process or system to reduce the amount of energy input into the system without negatively affecting the output(s)
The widely adopted standard for Energy Audits is governed by ASHREA (American Society of Heating, Refrigerating, & Air-Conditioning Engineers) of which there are three levels.
Level 1 Energy Audit
This will generally involve an analysis of the facility’s utility bills – with or without an Energy Star (or other) benchmark – and a brief survey of the facility. The recommendations resulting from a Level 1 audit do not usually include detailed cost and ROI analyses, but rather a general qualitative analysis of the facility’s energy use.
Level 2 Energy Audit
This provides a more detailed analysis of utility bills and a more comprehensive inspection of the facility, with identification of specific energy uses. Recommendations will include the estimated costs of implementing specific energy conservation measures (ECMs) and a quantitative ROI analysis.
Level 3 Energy Audit
This is generally an investment grade energy audit that provides a thorough field inspection of the facility, a detailed professional analysis of the energy use and potential improvements and ECMs, and may be signed and sealed by an independent third-party Professional Engineer registered in the state or territory in which the facility is located. A detailed report that includes estimated costs of ECMs, ROI and life-cycle cost analysis will be provided.