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What is an energy audit?

In my work in the energy efficiency space, I've noticed that most people don't really understand what an energy audit is.

There is a big misunderstanding about energy audits, including what they cover, who is qualified to perform one, why they are relatively expensive, and what is provided.

What is an energy audit?

An energy audit is an extremely detailed assessment of the energy efficiency of a site, or of aspects of a site (eg; insulation, lighting, heating and cooling, hot water etc…).

Audits are designed to consider all of the energy use of a site. Determining energy use can rely upon examining the physical properties of the buildings in question, as well as appliance effectiveness, thermal patterns, electrical and gas demand, and human behaviour.

Above is a tank-based standard electric hot water service - prime for replacement with a more efficient option.

A good audit should save most sites at least 10-15% of their energy bill, however far greater savings are sometimes possible.


The precise definition of an energy audit depends on Standards Australia. The processes involved depend upon which standard is being applied, and what type of audit has been chosen.

The standards are described by AS/NZS 3598:2014. There are several categories of energy audit, including Commercial Buildings (AS NZS 3598.1), Industrial and Related Activities (AS NZS 3598.2) and Transport Related Activities (AS NZS 3598.3).

Most energy audits are done using the standard for Commercial Buildings.

The audit procedure

It is the responsibility of an auditor to determine the purpose of the audit, and work out how to direct investigations. The owner of the site will have a specific purpose, and reason for obtaining the audit. This is critical in order for the energy audit to be correctly focused.

It is also important to determine the type of energy audit required. There are three types, and each has a different cost and different requirements.

Types of Energy Audit

There are three types of energy audit, Type 1, Type 2, and Type 3.

All require a site visit, what varies is the scope, the level of accuracy, how the appliances around the site are measured, and the detail of recommendations. A payback schedule is required, this helps clients to understand how much each recommendation costs, and how long it takes to payback each recommendation assuming certain savings.

Most people request a Type 2 audit.

Data and Graphs

Some typical graphs.

Here we examine energy usage by location - how much energy is used for each room, or type of rooms.

Here is an electricity energy use breakdown illustration - looking at the proportion of consumption by device type.

We can look at gas usage in certain periods.

Smart meter data can be used to examine utilisation by 30 minute period.

In this case, we are comparing usage across two days.


A good Type 2 audit will cost around $800 minimum, for a small house. Audits for medium companies can be $1,500-$2,000, and large sites (such as a school) can be at least $3,000.

Very large sites can be over $10,000, and can require a team of auditors.

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