In the United States, when a city ordinance, a utility programme or a lender asks for an energy audit, it almost always asks for a level: Level 1, Level 2 or Level 3. Those levels come from ANSI/ASHRAE Standard 211, Standard for Commercial Building Energy Audits. Before it existed, "energy audit" meant whatever the consultant decided it meant. Standard 211 made the term procurable — you can now specify an audit and know what you will receive.
What Standard 211 fixed
Its contribution is consistency. The standard defines the minimum scope of each audit level, the data that must be collected, how energy use must be analysed, and what the report must contain — including standardised data-collection forms and a reporting spreadsheet so results from different auditors can actually be compared. That is precisely why regulators adopted it: a city can mandate "an ASHRAE Level 2 audit" and receive comparable submissions from thousands of buildings.
Before any level: the preliminary energy use analysis
Every audit begins with a Preliminary Energy Use Analysis (PEA). Using at least twelve consecutive months of utility data (24 months is commonly preferred), the auditor establishes the building's total energy use, its EUI (energy use intensity, typically kBtu/ft²·yr) and its cost, then benchmarks it against peers — usually via ENERGY STAR Portfolio Manager. The PEA answers the first question worth asking: is this building actually a poor performer, or does it merely feel like one?
Level 1 — Walk-Through Analysis
A brief on-site survey plus the PEA. The auditor interviews operating staff, inspects major systems, and identifies low-cost and no-cost measures along with a list of potential capital projects flagged for later study. Savings estimates are order-of-magnitude.
Use it when you need to triage a portfolio and decide where deeper study is justified. It is cheap, fast, and frequently pays for itself in operational fixes alone — drifted setpoints, schedules running seven days when the building runs five, simultaneous heating and cooling.
Level 2 — Energy Survey and Engineering Analysis
The workhorse, and the level most ordinances mandate. Level 2 requires substantially more:
- A detailed survey of the building envelope, HVAC, lighting, domestic hot water, plug and process loads;
- A breakdown of energy use by end use that must reconcile with metered consumption — you cannot simply list measures without demonstrating where the energy goes;
- For each recommended measure: estimated energy and cost savings, implementation cost, and financial metrics such as simple payback or savings-to-investment ratio;
- Identification of interactions between measures, so savings are not double-counted;
- A discussion of measures considered and rejected, with reasons.
That end-use reconciliation is the clause that separates a real Level 2 from a dressed-up walk-through. It forces the auditor to build a defensible energy balance for the building.
Level 3 — Detailed Analysis of Capital-Intensive Modifications
Sometimes called an investment-grade audit. Level 3 targets the expensive measures a Level 2 flagged but could not justify to financing standards. It adds extended field measurement and data logging, and typically calibrated energy simulation — a model tuned until it reproduces actual metered consumption — so that savings projections carry the confidence a lender or an energy performance contract requires.
This is where Standard 211 hands off to ASHRAE Guideline 14: the calibration criteria for the model, and the later verification of realised savings, live in that document. It is also where whole-building retrofit modelling earns its cost.
Why US cities mandate Level 2
Energy benchmarking and audit ordinances across the United States lean on Standard 211 for their technical definition. The best-known example is New York City's Local Law 87, which requires covered buildings to complete an ASHRAE Level 2 audit and retro-commissioning on a ten-year cycle and file an Energy Efficiency Report. Similar requirements appear in other major cities' benchmarking and performance ordinances.
Level 2 is the sweet spot for regulators: rigorous enough to produce a credible, costed measure list, but not so expensive that it becomes a punitive burden across an entire building stock.
How it compares to ISO 50002
Standard 211 and ISO 50002 pursue the same goal from different angles. ISO 50002 is process-oriented, sector-agnostic and international — it governs how any audit of any energy use is conducted. Standard 211 is prescriptive and building-specific — it defines exactly what a commercial building audit at each level must contain. If you operate internationally you will meet both; if you operate in the US commercial market, Standard 211 is the one written into the contract.
The takeaway
Specify the level deliberately. Level 1 to triage a portfolio, Level 2 when you need a costed and defensible measure list (and whenever an ordinance says so), Level 3 when capital is at stake and the savings must survive a lender's scrutiny. Then hold the auditor to the standard's substance — particularly the end-use breakdown that reconciles with your bills, because that is the part that proves the report is engineering rather than opinion.
Need an ASHRAE Level 1, 2 or 3 audit?
We deliver ASHRAE Standard 211 energy audits for US commercial buildings — including Level 2 audits for Local Law 87 compliance and Level 3 investment-grade studies backed by calibrated energy models. Let's talk.
Get in touchThis article is general guidance and reflects information available at the time of writing. ASHRAE Standard 211 requirements are defined by the published standard, and local ordinance requirements vary by jurisdiction — always confirm the current edition and the specific rules that apply to your building.