---
title: "Energy audit technique and saving opportunities"
subject: "Industrial Power Distribution and Illumination"
chapter: 10
key: "semester_6/industrial_power_distribution_and_illumination:energy-audit-technique-opportunities"
source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/energy-audit-technique-opportunities
site: BCT Engineering
---

# Energy audit technique and saving opportunities

Industrial Power Distribution and Illumination · Chapter 10: Electrical Energy Audit in Industry

- Asked in: 2072 Magh, 8 marks
- Video: [Energy Efficiency, Energy Audit and Energy Conservation](https://www.youtube.com/watch?v=zKn3VSgp3Mc) — UTAR IIE
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/energy-audit-technique-opportunities
- Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-10

## Question

What is an energy audit? Explain energy audit technique. List out the energy saving opportunities for industrial electrical system.

## Short answer

An energy audit systematically measures and analyses energy use to identify waste. Technique: plan, collect data, measure, analyse, identify opportunities, evaluate economics, implement and monitor. Saving opportunities include pf correction, efficient motors/VFDs, LED lighting, compressed air leak repair, load scheduling and proper maintenance.

## Answer

An **energy audit** is a systematic study of how energy is used in a plant: it measures energy inputs and uses, finds where energy is wasted, and recommends cost-effective measures to reduce consumption and cost without affecting production or safety.

#### Types
- **Preliminary (walk-through) audit** – a quick survey using existing bills and a site visit; finds obvious savings in a few days.
- **Detailed audit** – a full study with instruments, energy balance of each section and detailed cost–benefit of each measure.

#### Energy audit technique (steps)
1. **Pre-audit planning** – meet management, form audit team, collect plant layout, single-line diagram, production data and 1–3 years of electricity bills.
2. **Data collection** – list connected loads (motors, lighting, compressors, furnaces), nameplate ratings and operating hours.
3. **Measurement** – use portable instruments: power analyser (kW, kVA, pf, harmonics), clamp meters, lux meter, tachometer, thermal camera, flow and pressure meters.
4. **Analysis** – prepare load curve, energy balance (where each kWh goes), specific energy consumption (kWh per unit product), compare with benchmarks; identify losses.
5. **Identify energy saving opportunities (ESOs)** and estimate savings.
6. **Economic analysis** – cost of each measure, annual saving, simple payback, NPV/IRR; rank them (no-cost, low-cost, high-investment).
7. **Report and action plan** – recommendations with priority and responsibility.
8. **Implementation and monitoring** – verify savings by measurement, then repeat audit periodically.

```text
Plan → Collect data → Measure → Analyse
  ↑                                 ↓
Monitor ← Implement ← Report ← Find ESOs & costs
```

#### Energy saving opportunities in industrial electrical systems
| Area | Opportunity |
|---|---|
| Tariff / demand | Load scheduling, shift loads to off-peak, maximum demand controller |
| Power factor | Capacitor banks to keep pf near 0.95–0.99, reduce kVA charge |
| Transformers | Proper loading, switch off lightly loaded units, correct tap |
| Motors | Energy-efficient motors, correct sizing (avoid under-loading), star-delta for lightly loaded motors, rewinding quality |
| Drives | VFDs for pumps, fans, compressors instead of throttling |
| Compressed air | Fix leaks, lower pressure, switch off when idle |
| Lighting | LED/T5 lamps, electronic ballast, daylight use, timers and occupancy sensors |
| Distribution | Proper cable size, balance phases, reduce harmonics |
| Housekeeping | Switch off idle machines, good maintenance, lubrication, belt tension |

Typical savings from an audit are 10–30 % of the electricity bill, many with payback under two years.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the main purpose of an energy audit?
   A. To increase production at any energy cost
   B. To only check the electricity bill for errors
   C. To replace all old equipment with new
   D. To find where energy is wasted and recommend cost-effective measures without affecting production or safety
   Answer: D. An energy audit is a systematic study of energy use that finds wastage and recommends cost-effective savings while keeping production and safety unaffected. (Key point: Definition of energy audit)

2. How does a detailed audit differ from a preliminary (walk-through) audit?
   A. It uses instruments and an energy balance with cost-benefit analysis of each measure
   B. It uses only existing bills and a quick visit
   C. It takes only a few days
   D. It looks only at lighting
   Answer: A. A preliminary audit uses bills and a site visit; a detailed audit uses instruments, energy balances and detailed cost-benefit study. (Key point: Audit types)

3. Which is the correct order of the middle steps of the audit technique?
   A. Report, measurement, analysis, data collection
   B. Analysis, data collection, measurement, economic analysis
   C. Data collection, measurement, analysis, identify ESOs, economic analysis
   D. Implementation, measurement, report, planning
   Answer: C. After pre-audit planning, the audit goes data collection, measurement, analysis, ESOs, economic analysis, report, then implementation and monitoring. (Key point: Order of audit steps)

4. In the economic analysis step, how are energy saving measures ranked?
   A. By their cost and payback, as no-cost, low-cost and high-investment
   B. By alphabetical order of equipment
   C. By the age of the equipment
   D. By the number of workers affected
   Answer: A. Each measure is costed, its saving and simple payback/NPV/IRR found, and measures are ranked as no-cost, low-cost or high-investment. (Key point: Ranking measures)

## Related in Industrial Power Distribution and Illumination

- [Energy saving opportunities in industrial plant](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aenergy-saving-opportunities) — Industrial Power Distribution and Illumination, chapter 10, asked 2×
- [Need of energy audit and technique](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aenergy-audit-need-technique) — Industrial Power Distribution and Illumination, chapter 10, asked 3×
- [Energy audit definition and process](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Adefine-energy-audit-process) — Industrial Power Distribution and Illumination, chapter 10
- [Execution phase of energy audit](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aenergy-audit-execution-phase) — Industrial Power Distribution and Illumination, chapter 10
- [Energy and cost saving from lighting retrofit](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Alighting-retrofit-100kw) — Industrial Power Distribution and Illumination, chapter 10
- [Planning electrical installation of industrial building](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aplanning-industrial-installation) — Industrial Power Distribution and Illumination, chapter 5

## Related in other subjects

- [Preparing and presenting an energy audit report](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Aenergy-audit-report-preparation-presentation) — Energy Resources, chapter 9
- [Energy audit types and audit procedure](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Aenergy-audit-types-procedure) — Energy Resources, chapter 9
- [Energy audit instruments and energy balance](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Aenergy-audit-instruments-measurements) — Energy Resources, chapter 9
- [Energy saving calculation: lighting and motor](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Alighting-motor-energy-saving-case) — Energy Resources, chapter 9