What Is an Energy Audit?

An energy audit is a structured assessment of how a building uses energy, where it's being wasted, and what it would take to fix it. That's the simple definition. In practice, "energy audit" covers a wide range of actual work, from a two hour walk through with a clipboard to a months long engineering study backed by a calibrated computer model, and the difference between those two matters enormously depending on what decision the audit is meant to support.

What an Energy Audit Actually Does

At a minimum, every energy audit does three things: it reviews how much energy a building is using, usually starting with 12 months or more of utility bills, it benchmarks that usage against similar buildings through energy management tracking, and it identifies specific opportunities, called energy conservation measures, to reduce consumption. Beyond that minimum, audits diverge sharply in depth, method, and cost, which is exactly why a standardized framework matters.

The ASHRAE Framework

In the U.S., ASHRAE Standard 211 is the industry standard that turns "energy audit" from a vague term into three clearly scoped tiers, so a proposal from one firm can actually be compared to a proposal from another.

ASHRAE Level 1, a walk through or screening audit, is the fastest and least expensive option, built for portfolio screening, due diligence, or meeting a basic benchmarking requirement.

ASHRAE Level 2, a detailed energy survey, adds engineering grade savings and payback calculations for specific measures, and is the level most mandatory audit ordinances actually require.

ASHRAE Level 3, an investment grade audit, adds calibrated simulation and construction grade cost estimates, built to support major capital decisions and energy performance contracts.

Digital Audits Are Changing How All Three Get Done

Every level of audit, not just Level 1, is increasingly performed using digital tools rather than exclusively in person visits. Drone based thermal imaging, wireless sensors, satellite imagery, and remote utility data access let an audit team collect much of what a traditional audit requires without the cost and scheduling burden of a full site visit at every property. We cover what a digital energy audit actually involves and how it compares to a traditional on site audit in detail elsewhere in this series.

What an Energy Audit Costs

Cost is driven almost entirely by which ASHRAE level is performed, and scales with building size and complexity within that. As a rough guide, Level 1 audits typically run $0.05 to $0.10 per square foot, Level 2 audits run $0.10 to $0.30 per square foot, and Level 3 investment grade audits run $0.25 to $0.50 per square foot or more. We break down commercial energy audit costs by level, building size, and complexity in a dedicated article.

Who Actually Needs One, and When

A single building owner deciding whether to invest in efficiency at all typically starts with a Level 1. A portfolio operator with a mandatory audit ordinance deadline, over 40 U.S. jurisdictions now require ASHRAE standard audits for large commercial buildings, usually needs Level 2. An organization about to sign an energy performance contract or commit significant capital needs Level 3. Our energy audit checklist and energy audit FAQ go deeper on how to prepare for one and answer the most common questions building owners ask before getting started.