An energy audit answers three questions about a building: how much energy it uses, where that energy goes and what can be done to reduce it. In most commercial buildings, HVAC systems account for a large share of energy use, so HVAC is usually the focus of the audit and the source of many of the best opportunities.
Audits come in different depths. ASHRAE defines three levels, from a quick walk-through to a detailed engineering analysis suitable for major capital investment. Choosing the right level saves money: a Level 3 audit is wasted on a building that has not yet fixed its schedules, while a Level 1 audit will not support a decision to replace a chiller plant. This guide explains each level and how to use them.
The governing standard
ASHRAE Standard 211, Standard for Commercial Building Energy Audits, first published in 2018, sets minimum requirements for each audit level, including the data to collect, the analysis to perform and the content of the report. Before Standard 211, the levels were described in ASHRAE's Procedures for Commercial Building Energy Audits. Standard 211 brought consistency, so that owners comparing audit proposals can expect similar deliverables from providers offering the same level.
Standard 211 also defines a preliminary energy use analysis (PEUA), which comes before a Level 1 audit and relies on utility data and basic building information.
Preliminary energy use analysis
The PEUA establishes the building's energy use profile from at least 12 months, and preferably several years, of utility data. It calculates energy use intensity (EUI), energy cost per unit floor area and, where possible, compares the building with similar buildings. In Canada, ENERGY STAR Portfolio Manager, supported by Natural Resources Canada, is the common tool for this comparison. See benchmarking building energy use.
The PEUA tells the owner whether the building is a poor, average or good performer, which helps decide whether a deeper audit is worthwhile.
Level 1: walk-through
A Level 1 audit adds a brief site visit to the PEUA. The auditor tours the building, talks with operations staff and reviews major systems.
Typical Level 1 HVAC activities
- Inspection of central plant, air handlers, rooftop units and major exhaust systems.
- Review of BAS schedules, setpoints and obvious overrides.
- Identification of visible problems: equipment running unoccupied, simultaneous heating and cooling, missing insulation, failed economizers.
- Discussion of comfort complaints and maintenance issues.
Level 1 deliverables
- Low-cost and no-cost measures with rough savings estimates.
- A list of potential capital measures that merit further study.
- An end-use breakdown is not required at this level.
Level 1 audits suit portfolio screening, smaller buildings and owners deciding where to invest audit effort.
Level 2: energy survey and analysis
A Level 2 audit is the most common choice for owners planning real projects. It involves a more detailed site survey and engineering analysis of each recommended measure.
Typical Level 2 HVAC activities
- Detailed inventory of HVAC equipment: capacities, efficiencies, ages, condition and controls.
- Review of drawings, sequences of operation and maintenance records.
- BAS trend review and, where needed, short-term measurements with data loggers.
- Breakdown of energy use by end use, such as heating, cooling, fans, pumps, lighting and plug loads, reconciled with utility data.
- Calculation of savings for each measure using engineering methods or simplified modelling, accounting for interactions between measures.
Level 2 deliverables
- Recommended measures with estimated cost, energy and cost savings, simple payback and, where requested, greenhouse gas reductions.
- Operational and maintenance recommendations.
- Identification of measures needing Level 3 analysis.
Level 2 results are generally sufficient for low and moderate cost measures and for utility incentive applications. See utility incentives for HVAC upgrades in Canada.
Level 3: detailed analysis of capital-intensive modifications
A Level 3 audit focuses on major capital projects, such as chiller or boiler plant replacement, conversion to heat pumps, heat recovery systems or a full electrification strategy. The analysis must be detailed enough to support investment decisions.
Typical Level 3 HVAC activities
- Extended monitoring of equipment and systems, often over weeks or months.
- Calibrated whole-building energy modelling or detailed system models.
- Preliminary engineering for proposed measures, including layout, electrical capacity and structural implications.
- Detailed cost estimates, often with contractor input.
- Life cycle cost analysis and sensitivity analysis on energy prices and carbon costs. See life cycle cost analysis for HVAC options.
- A measurement and verification plan for the proposed measures.
Level 3 deliverables
- Investment-grade analysis of selected measures, with savings and costs presented with greater confidence than at Level 2.
- Implementation recommendations, risks and phasing.
Comparing the levels
| Feature | PEUA | Level 1 | Level 2 | Level 3 |
|---|---|---|---|---|
| Utility data analysis | Yes | Yes | Yes | Yes |
| Site visit | No | Brief walk-through | Detailed survey | Detailed survey plus monitoring |
| End-use breakdown | No | No | Yes | Yes, detailed |
| Measure analysis | None | Rough estimates | Engineering calculations | Detailed modelling and design |
| Cost estimates | None | Order of magnitude | Budget level | Detailed |
| Typical use | Screening | Prioritizing buildings | Planning projects and incentives | Major capital decisions |
Choosing the right level
- Start with data. If benchmarking shows high EUI, a deeper audit is justified.
- Match depth to decisions. Use Level 1 to find quick wins and decide where to look further. Use Level 2 to plan a program of measures. Reserve Level 3 for major capital projects.
- Consider retro-commissioning first. Many Level 1 and 2 findings are operational. Fixing them through retro-commissioning before major investment prevents oversizing new equipment based on wasteful current operation.
- Check program requirements. Incentive programs, lenders and some municipal or provincial benchmarking and performance requirements may specify a particular audit level or format.
- Think about carbon. Many owners now want audits to address decarbonization pathways, not just energy cost. Make this explicit in the scope.
Making audits lead to action
Audit reports that sit on a shelf deliver nothing. To get value:
- Involve operations staff from the start so recommendations are practical.
- Ask for measures to be grouped into a logical implementation sequence.
- Align recommendations with equipment replacement timing in the capital plan.
- Plan measurement and verification for major measures so savings can be confirmed, typically following the IPMVP framework.
Frequently asked questions
How often should a building be audited?
Many owners repeat a Level 1 or Level 2 audit every five years or so, or when major changes in use, equipment or energy prices occur. Some jurisdictions set their own schedules.
Can an audit be done without a BAS?
Yes. Without a BAS, auditors rely more on site inspection, spot measurements and temporary data loggers.
Key takeaways
- ASHRAE Standard 211 defines a preliminary energy use analysis and three audit levels with increasing depth.
- Level 1 finds quick wins, Level 2 supports most project planning and incentives, and Level 3 supports major capital decisions.
- HVAC systems are usually the largest source of audit opportunities in commercial buildings.
- Fix operational problems before sizing major replacements.
- Define scope clearly, including carbon goals, and plan for implementation. Our energy audits follow the ASHRAE audit levels.
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