Energy audits are run to identify potential energy conservation measures (or a combination of them) in a building or a process, then to determine the profitability of implementation. This requires running an analysis of a building’s energy usage profile and rate structure, assessing the thermal envelope and electromechanical systems in place, identifying potential modifications, replacements, or additions that could increase their efficiency and stability, estimating the required capital (implementation, engineering, and monitoring costs) and running economic modelling to compare the options, then record it all in a report.
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), describes three main types of energy audits:
Level 1 - Detailed analysis / Preliminary audit
The level 1 audit is the simplest, the most basic. This involves minimal interviews with site operations and maintenance (O&M) personnel, a brief review of utility bills and other operating data, and a walk-through of the facility, all geared towards the identification of glaring areas of energy waste or inefficiency. The data compiled is then used for the preliminary energy use analysis and a report detailing low-cost/no-cost energy-saving measures and potential capital improvements for further study. Typically, a Level 1 audit will only uncover major problem areas. Corrective measures are briefly described, and quick estimates of implementation costs, potential operating cost savings, and simple payback periods are provided. This level of detail, while not sufficient for reaching a final decision on implementing proposed measures, is adequate to prioritize energy efficiency projects and to assess the need for a more detailed audit.
Level 2 - Energy survey and analysis
A Level 2 audit includes the preliminary ASHRAE Level 1 analysis, but also includes more detailed energy calculations and financial analysis of proposed energy efficiency measures. The financial analysis or Life Cycle Cost Analysis provides the facility owner with comprehensive understanding of the financial benefits of implementing specific energy efficiency measures. Utility bills are collected for a 24- to 36-month period to allow the auditor to evaluate the facility’s energy/demand rate structures and energy usage profiles. This type of audit identifies all energy conservation measures appropriate for the facility given its operating parameters. A detailed financial analysis is performed for each measure based on implementation cost estimates, site-specific operating cost savings, and the customer’s investment criteria. Sufficient detail is provided to justify project implementation.
Level 3 - Detailed analysis of capital-intensive modifications
This level of engineering analysis focuses on the potential capital-intensive projects identified in the Level 2 analysis and involves more detailed field data gathering as well as a more rigorous engineering analysis. It provides detailed project cost and savings calculations with the high level of confidence required for major capital investment decisions. This audit expands on the Level 2 audit by providing a dynamic model of energy use characteristics of both the existing facility and all energy conservation measures identified. The building model is calibrated using actual utility data to provide a realistic baseline against which to compute operating savings for proposed measures. Extensive attention is given to understanding not only the operating characteristics of all energy consuming systems, but also the situations that cause load profile variations on both an annual and a daily basis. Existing utility data is supplemented by sub-metering of major energy consuming systems and monitoring of system operating characteristics.