Types of Energy Audit: Choosing the Right Level for Your Business

As energy advisors, consultants, engineers, and sustainability leaders, you know how crucial it is to maximise energy efficiency in buildings and facilities.

Yet, one persistent challenge remains: How do you select the right type of energy audit, and how do you leverage audit findings to secure real savings and actionable outcomes for your clients or organisation?

This practical guide will demystify the different types of energy audit, from the basic walk-through to the robust investment-grade assessment. You’ll come away with clear guidance on matching audit depth to project objectives, technical needs, and budget—so you can deliver the best value as a trusted energy professional.

Understanding the Different Types of Energy Audit

Energy audits play a foundational role in identifying inefficiencies, benchmarking consumption, and prioritising improvements. The main types of energy audit—walk-through, detailed (Level 2), and investment-grade audits—range from quick reviews to in-depth engineering analyses. Industry standards, such as the ASHRAE Level 1, 2, and 3 classifications, provide a structured way of understanding each audit’s purpose and process.

Let’s break down each types of energy audit, discuss when to use them, and provide real-world insights for energy professionals operating in mid to high GDP per capita countries.

1. Walk-Through Energy Audit (Preliminary or ASHRAE Level 1)

Walk-through energy audits are an essential tool for energy advisors and facilities managers to triage opportunities quickly. They can be especially useful for identifying “low-hanging fruit”—such as lights left on after hours, air leaks in compressed air systems, or HVAC controls set incorrectly. For sustainability officers, a walk-through audit can offer quick wins that build momentum for broader energy management initiatives.

Purpose: To spot obvious sources of energy waste and identify no-cost or low-cost recommendations quickly.

What’s involved:

• Review of previous 12–36 months of utility data.
• A visual inspection of the facility, plant, or building.
• Interviews with staff to identify pain points and improvement opportunities.
• A simple report outlining preliminary recommendations.

When and why to use:

• When the client needs a very quick, low-budget assessment.
• For initial scoping, especially when multiple sites are under review for deeper investment.
• As a prerequisite to more detailed audits.

2. Detailed Energy Audit (ASHRAE Level 2)

Detailed energy audits are ideal for energy-focused engineers and building services consultants tasked with designing or validating upgrades, retrofits, or system replacements. Engineers can use this data-rich approach to justify system changes, such as plant upgrades or lighting overhauls, with confidence. Facilities managers benefit by receiving clear, prioritised options and knowing which measures offer the best return on investment.

Purpose: To quantify energy consumption and provide an in-depth analysis of energy-savings measures (ESMs), including economic evaluation.

What’s involved:

• Full site walk-through with a comprehensive inventory of equipment.
• Analysis of utility data to develop an energy balance for the facility.
• Submetering or short-term data logging where needed.
• Detailed assessment of the building envelope, controls, and major systems (HVAC, lighting, process loads, etc.).
• Identification and prioritisation of ESMs, with cost–benefit calculations (simple payback, IRR, NPV).
• Full technical and financial feasibility reporting.

When and why to use:

• When a client is ready to make medium- to large-scale investments in efficiency.
• To meet requirements for grant applications, lender diligence, or building certifications.
• When an earlier walk-through highlights substantial or complex opportunities that need quantification.

3. Investment-Grade Energy Audit (ASHRAE Level 3)

Investment-grade energy audits are essential for engineers and energy consultants navigating large commercial portfolios, industrial sites, or government infrastructure projects. The findings often underpin contractual agreements with ESCOs, financiers, or government agencies. Sustainability officers and facilities managers use these audits to secure major funding and ensure project risks are well managed.

Purpose: To provide the highest level of technical and financial certainty, supporting major investment, performance contracting, or third-party financing.

What’s involved:

• Extended site investigation, with comprehensive data collection (often months).
• Permanent or temporary submetering on major end-uses.
• Advanced monitoring and computerised simulations (hourly, seasonal, stochastic).
• Lifecycle cost analysis, including capex, opex, and risk sensitivity.
• Detailed specifications and engineering drawings for implementation.
• Fully bankable reporting, often required for energy performance contracts or large-scale retrofits.

When and why to use:

• For major capital projects or when projects are financed via guaranteed energy savings.
• To provide robust documentation for performance guarantees in energy service company (ESCO) models.
• Where there are complex interactions between building systems that require meticulous simulation and modelling.

Achieving competence at the investment-grade level requires thorough engineering skill, deep knowledge of modelling/measurement, and strong project management. This is why the Investment Grade Energy Auditor (IGEA) Certification is regarded as the industry benchmark when delivering these audits. Certified auditors are highly sought after for projects where accountability, risk management, and technical rigour are paramount.

ASHRAE Audit Levels: A Closer Look

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has established a globally recognised framework for types of energy audits:

• ASHRAE Level 1: Aligns with the walk-through energy audit. Focused on rapid screening and basic recommendations.
• ASHRAE Level 2: Corresponds to the detailed energy audit. Provides in-depth analysis of feasible ESMs.
• ASHRAE Level 3: Synonymous with the investment-grade energy audit. Detailed data, modelling, financial forecasting, and specifications.

For professionals in Australia, New Zealand, the UK, Canada, Singapore, and similar economies, adhering to ASHRAE standards ensures consistency and high-quality outcomes, both for standalone audits and for compliance with green building and corporate reporting programs..

How to Choose the Right Audit Type: A Step-By-Step Guide

Let’s match audit type to real-world project scenarios, drawing on the challenges and goals typical for our professional audience.

1. Clarify Project Objectives

• Are you chasing quick wins, or do you need a solid business case for major upgrades?
• Is stakeholder buy-in or funding dependent on identified paybacks and certainty?
• Do you require compliance with green building standards or regulatory reporting?

2. Assess Site Complexity and Size

• Small commercial tenancy or office? Start with a walk-through energy audit.
• Mixed-use building or school campus? A detailed energy audit is usually justified by potential savings.
• Manufacturing plant with complex process loads or district energy system? Go straight to investment-grade for robust results.

3. Consider Budget and Timeline

• Tight budget, limited staff, or boardroom scepticism? Walk-through offers value swiftly.
• Medium-term capital allocation or asset lifecycle management? Detailed audit fits best.
• External financing, government stimulus, or guaranteed savings? Investment-grade is non-negotiable.

4. Secure the Right Audit Expertise

For projects seeking the highest certainty and risk management, insist on an assessor holding the Investment Grade Energy Auditor (IGEA) Certification. This designation sets a benchmark for technical competence and ethical conduct—giving clients and stakeholders confidence in outcomes.

Practical Examples for Professionals

Energy Advisors/Consultants:
You’re assisting a portfolio client with aged-care facilities spread across several climate zones. Begin with walk-through energy audits at each site to compare baselines, then propose targeted detailed audits at “high-leakage” buildings identified in the first round.

Building Services Engineers:
A university is rolling out a campus-wide retrofit. A Level 2/detailed audit will let you model various scenarios for system and envelope upgrades. If they consider an energy performance contract, move to investment-grade analysis, using simulations for major HVAC and lighting.

Facilities Managers/Sustainability Officers:
You need to report annual energy savings for a corporate ESG report. A combination of walk-through and detailed audits delivers both fast reporting and actionable priorities for yearly maintenance and capital budgets.

Energy-Focused Engineers:
You’re developing the business case for a large factory’s process heat upgrade, including fuel switching and advanced controls. Only an investment-grade audit will provide the simulations, technical drawings, and financial models your C-suite expects.

To deliver high-value, investment-grade audits, staying at the forefront of industry skills is critical. The Investment Grade Energy Auditor (IGEA) Certification equips you with advanced auditing, simulation, and financial analysis capabilities, and is recognised as a mark of excellence across commercial, government, and industrial sectors.

Conclusion: The Audit as Strategic Tool

Selecting the right type of energy audit—whether walk-through, detailed, or investment-grade—isn’t just about compliance for energy advisors, engineers, and sustainability managers. It’s about creating clear, actionable roadmaps to energy cost savings and emissions reductions, supporting organisational decision-making, and maximising the impact of your expertise.

If you want to further build confidence and rigour in your work, consider enrolling in free lessons from our Process of Undertaking a Successful Energy Audit course, one of the courses in IGEA Certification.