After reading this article you will learn about:- 1. Meaning of Energy Audit 2. Objectives of Energy Audit 3. Types 4. Report.

Meaning of Energy Audit:

Energy audit is an official scientific study of energy consumption of an organisation/process/plant/equipment aimed at reduction of energy consumption and energy costs without affecting productivity and comforts and suggesting the methods for energy saving and reduction in energy cost. Energy audit is carried out in planned, official manner by every energy intensive organisation/plant management.

i. Familarisation with the energy inlets and outlets, of energy.

ii. Data acquisition, measurements.


iii. Study of advanced, modern processes and plants for similar activities under audit.

iv. Formulating energy equations and software.

v. Economic evaluation of energy consumption in the sector/organisation/plant under audit.

vi. Analysis of energy consuming sub-processes.


vii. Suggest energy conservation processes along with alternatives, necessary investments, payback periods, economic benefits etc.

viii. Suggest steps to be taken for reducing energy consumption without sacrificing pro­ductivity.

The energy audit identifies the cost of energy and where and how it is used. It will identify the amount of energy expended in a process with the help of mass and energy balance for each process.

The energy flow diagram is then prepared showing the quantity, form, source and quality (i.e., temperature) of the energy required for various processes. Next step is to make a critical analysis for energy used and energy wasted. This is followed by identification of poten­tial areas for energy saving.

Objectives of Energy Audit:


The main purpose of energy audit is to establish quickly and reliably, the basic relative costs of the various forms of energy purchased their main use and to identify mam locations where losses, wastages or inefficiency occurs.

In simple language we can say that, energy audit helps to understand more about the ways different energy sources are used in the industry and helps to identify areas where waste can occur and where scope for improvement may be possible. Thus, energy audit is one of the con­cepts used in the energy management and it involves methodological examination and compre­hensive review of energy use in industries.

Types of Energy Audit:

The energy audit can be of following two types:

1. Preliminary audit.


2. Detailed audit.

1. Preliminary audit:

Preliminary audit is carried out in the limited time say within 10 days and it highlights the energy cost and wastages in the major equipment’s and processes. It also gives the major energy supplies and demanding accounting. The questionnaire containing the industrial details of energy consumption process carried out, energy need to unit product; load data etc. must be completed before the pre-audit visit.

The pre-audit visit is done, by the audit team/audit consultant, in the plant area with the attention focused on the energy inputs, spots of wastage and available energy conservation opportunities. The items for waste recycling opportunities are identified. The data regarding energy inputs and outputs are collected for use during preliminary audit.


During the visit, discussions with line supervisors and line technicians and joint brain­storming may be necessary to acquire creative ideas and to know the practical difficulties in carrying out the proposed energy conservation measures (ECMs).

After the pre-audit visit, the work of energy audit is undertaken. In the preliminary audit, low tech recommendations are preferred. High tech solutions are given un­der detailed energy audit. Some of the low cost recommendations may be: Switching off lights when not required, replace incandescent lamps by the fluorescent lamps, automatic thermostat control, use of solar water heating panels etc.

The preliminary audit spots energy waste spots and recommend short, intermediate and long term solutions. It should adopt step by step and cautious approach for improvements and new techniques of energy management and control system.

2. Detailed (Comprehensive) Energy Audit:


Detailed energy audit, also known as com­prehensive energy audit includes engineering recommendations and well defined projects with priorities. It account for the total energy utilised in plants. It involves detailed engineering for options to reduce energy consumption and also reduce cost. The duration of such studies is generally from 1 to 10 weeks. The action plan in divided into short term, medium term and long term actions.

The short term action plan requires no capital investment or least investment to avoid energy wastages and minimising non-essential energy uses and improving the system efficiency through improved maintenance programme.

The medium term action plan requires a little investment to achieve efficiency improve­ment through modifications of existing equipment’s and other operations.

The long term action plan is aimed to achieve economy through latest energy saving tech­niques and innovations. The capital investments are required to be studied thoroughly while finalising the long term action-plan.


The comprehensive (detailed) energy audit is a thorough and extensive energy audit that analyses and quantifies the amount of energy consumption in each sub system of the plant and compares the same with the target energy consumption. Target per unit energy consumption is the optimum energy consumption per unit product.

The comprehensive audit is quite exhaustive, and it is convenient to split it into following sub parts:

1. Overall system audit:

This accounts for energy leakage/loss through the total sys­tem to the atmosphere. The energy conservation measures to eliminate such leak­ages/loss are recommended.

2. Functional audit:

It identifies the energy conservation measures in operation and maintenance of each main plant and its subsystems and suggests ECOs is operation and maintenance.


3. Utility Audit:

It identifies yearly/monthly/daily consumption of commercial second­ary energy (electricity/petroleum products/fuel etc.) and suggests ECOs.

4. Modernization audit:

It recommends major changes in the process requiring retro­fitting.

Report of Energy Audit:

The comprehensive energy audit report generally converts the following:

(i) Energy conservation opportunities (ECOs)


(ii) Energy conservation measures (ECMs)

(iii) Projected investments for ECMs.

(iv) Projected annual savings of ECMs and pay-back period.

(v) Feasibility studies for retrofitting/modification work.