Types of Energy Audits
The term energy audit is commonly used to describe a broad spectrum of studies ranging from a quick walk-through to a comprehensive analysis to satisfy financial investors. Numerous audit procedures have been developed from a variety of organizations like ASHRAE, IEA-EBC, Krarti, Turner, ISO and others. At it’s core, an audit assess performance and identified savings opportunities called Energy Conservation Measures (ECMs) or Energy Conservation Opportunities (ECOs).
When looking at the multiple existing audit methodologies, some common attributes are found. These are:
The analysis of building utility data and analysis of energy bills;
The study or assessment of the installed equipment;
The survey of the real operating conditions;
The understanding of the building behavior and of the interactions with weather, occupancy and operating schedules;
The selection and the evaluation of energy conservation measures;
The estimation of energy saving potential;
The identification of customer concerns and needs.
Common types/levels of energy audits are distinguished below, although the actual tasks performed and level of effort may vary with the consultant providing services under these broad headings. The only way to ensure that a proposed audit will meet your specific needs is to spell out those requirements in a detailed scope of work. Taking the time to prepare a formal solicitation will also assure the building owner of receiving competitive and comparable proposals.
Generally, there are three levels of analysis outlined by ASHRAE that all start with Benchmarking:
- Benchmarking: This a nearly universal first action and consists of a preliminary Whole Building Energy Use (WBEU) analysis based on historic utility use and costs and the comparison of the performances of the buildings to those of similar buildings. Benchmarking mainly consists in comparing the measured consumption with reference consumption of other similar buildings or predicted energy consumption generated by simulation tools. Both methods can help identify excessive or unacceptable operating costs. As mentioned before, benchmarking is also necessary to help identify a building’s energy saving potential. An important issue in benchmarking is the use of performance indexes to characterize the building. These indexes can be:
- Comfort indexes, comparing the actual comfort conditions to the comfort requirements;
- Energy indexes, consisting in energy demands divided by heated/conditioned area, allowing comparison with reference values of the indexes coming from regulation or similar buildings;
- Energy demands, directly compared to “reference” energy demands generated by means of simulation tools.
- Level I – Walk-through audit: Preliminary analysis made to assess building energy efficiency to identify not only simple and low-cost improvements but also a list of energy conservation measures (ECMs, or energy conservation opportunities, ECOs) to orient the future detailed audit. This inspection is based on visual verifications, study of installed equipment and operating data and detailed analysis of recorded energy consumption collected during the benchmarking phase;
- Level II – Detailed/General energy audit: Based on the results of the pre-audit, this type of energy audit consists in energy use survey to provide a comprehensive analysis of the studied installation, a more detailed analysis of the facility, a breakdown of the energy use and a first quantitative evaluation of the ECOs/ECMs selected to correct the defects or improve the existing installation. This level of analysis can involve advanced on-site measurements and sophisticated computer-based simulation tools to evaluate precisely the selected energy retrofits;
- Level III – Investment-Grade audit: Detailed Analysis of Capital-Intensive Modifications focusing on potential costly ECOs requiring rigorous engineering study. In most corporate settings, upgrades to a facility’s energy infrastructure must compete for capital funding with non-energy-related investments. Both energy and non-energy investments are rated on a single set of financial criteria that generally stress the expected return on investment (ROI). The projected operating savings from the implementation of energy projects must be developed such that they provide a high level of confidence. In fact, investors often demand guaranteed savings. The investment-grade audit expands on the detailed audit described above and relies on a complete engineering study to detail technical and economic issues necessary to justify the investment related to the transformations.