Where energy goes in a manufacturing plant and how an audit finds it: compressed air, motors and drives, steam, process heat and cooling, metering and production-normalised EnPIs.
Introduction
A building energy audit asks how much energy it takes to keep people comfortable. A plant audit asks how much energy it takes to make a tonne of product, and that changes almost everything about how the audit is run.
In a factory, energy use follows production. It rises with output, shifts with product mix, and spikes at start-ups and changeovers. The largest loads are often utilities that nobody on the production floor thinks of as energy at all, and the waste in them is usually invisible, because it leaks, vents or idles rather than breaking down.
Start with the data, not the walk-round
The first output of a plant audit is an energy balance: where the purchased electricity, gas and diesel actually go. Without it, the site visit becomes a tour of equipment that looks inefficient rather than equipment that uses the most energy.
That balance is built from three sources.
- Utility and fuel data: electricity bills and interval data, gas meter readings, diesel and LPG deliveries, ideally for at least a full year so that seasonal cooling load is visible.
- Sub-metering: whatever the plant already has on major feeders, compressors, boilers and chillers. Many plants have meters that were installed and never read.
- Temporary logging: power loggers, flow meters and temperature sensors placed on systems that are not sub-metered, across a representative production period.
The load profile is often the most revealing single chart. Plotting demand across a week, with production shifts overlaid, shows what the plant consumes when it is not producing: compressors pressurising leaks, pumps circulating to nowhere, furnaces holding temperature. That base load is frequently the cheapest saving on site.
The aim is to identify the significant energy uses, the handful of systems that account for most consumption, and to direct measurement effort there.
Compressed air
Compressed air is one of the most expensive forms of energy in a plant, because most of the electrical input to a compressor leaves as heat. It is also the system most often run on habit.
Leaks are the obvious starting point. The US Department of Energy and Compressed Air Challenge sourcebook, Improving Compressed Air System Performance, states that leakage in a well-maintained system should be under 10% of compressor capacity, while poorly maintained systems can lose 20 to 30% (Fact Sheet 7, May 2026 revision). Leaks concentrate at couplings, hoses, fittings, regulators, open condensate drains and pipe joints. An audit quantifies total leakage by running the system with production stopped and timing compressor load and unload cycles, then locates individual leaks with an ultrasonic detector.
Pressure setpoints come next. Compressors are commonly set well above what the end uses need, to cover pressure drop through dryers, filters and undersized pipework. The same sourcebook gives a rule of thumb of about 1% of connected compressor power for every 2 psi (roughly 0.14 bar) of pressure differential the compressor has to overcome (Fact Sheet 4, May 2026 revision). An audit measures pressure at the compressor, after treatment and at the point of use, to find where the drop actually occurs. Often it is in a filter or regulator rather than the piping.
Artificial demand is the extra air consumed because the system runs at higher pressure than needed: every leak, open blow-off and unregulated tool uses more air at a higher pressure. Lowering pressure therefore saves twice, on compression energy and on the volume wasted.
Inappropriate uses are jobs a cheaper utility could do: open blowing for cooling or cleaning, air-driven agitation, continuously running vacuum generators, cabinet cooling.
Controls determine how several compressors share a load. Machines running part-loaded together, or a fixed-speed unit trimming when a variable-speed unit should, waste energy every hour. Storage and sequencing logic are part of the review.
Heat recovery captures compression heat for process hot water or pre-heating. In the UAE there is little space heating demand to absorb it, so the case depends on a process use. The climate also matters at the intake: a compressor drawing hot air from inside its own room uses more energy per unit of air delivered, so intake location and room ventilation are worth checking.
Motors and drives, pumps and fans
Electric motors drive most of a plant’s mechanical work, so small efficiency differences add up over long running hours.
Variable-speed drives pay back where load varies. For centrifugal pumps and fans, power falls steeply as speed falls, which is why a pump throttled by a partly closed valve, or a fan restricted by a damper, wastes so much more energy than one slowed by a drive. An audit looks for throttled valves, bypass lines, dampers held partly shut and fans or pumps running at full speed regardless of demand.
Right-sizing matters because motors oversized for their duty run lightly loaded, where efficiency and power factor are poorer. Logging actual load against nameplate rating identifies these. Replacement decisions also consider rewind history and running hours.
Efficiency class is the reference for replacement. IEC 60034-30-1 classifies line-operated AC motors by efficiency. The 2014 edition defined classes IE1 to IE4; the second edition, published in December 2025, sets efficiency limits up to IE5. When a motor fails or is replaced, specifying a higher class is usually a small cost difference for a long-running duty.
Pumps and fans themselves are often oversized or running away from their best efficiency point. An impeller trim, a smaller pump or a change to system resistance can do more than a new motor.
Steam and hot water systems
Where a plant raises steam, losses accumulate at every stage between burner and process.
- Steam traps that fail open pass live steam into the condensate system. A trap survey, by ultrasonic or temperature testing, finds them. A plant without a regular trap programme usually has a population of failed traps nobody knows about.
- Condensate return brings back hot, treated water. Every litre not returned has to be replaced with cold make-up water that must be treated and heated from scratch. The audit measures how much condensate is returned and where it is being dumped.
- Insulation on pipes is generally present. On valves, flanges and fittings it is often missing, removed for maintenance and never replaced. Thermal imaging finds these quickly.
- Boiler combustion efficiency depends on the air-to-fuel ratio. Too much excess air carries heat up the stack. A flue gas analysis measuring oxygen and stack temperature shows whether burners need tuning or oxygen trim control.
- Blowdown controls dissolved solids in the boiler water. Blowing down more than the water chemistry requires throws away heated water; heat can also be recovered from the blowdown stream and from flash steam.
Process heat and furnaces
Furnaces, ovens, kilns and dryers are often the largest single energy users in plants that have them, and nearly all of that energy is fuel. The audit looks at combustion efficiency, as for boilers, and at where the heat goes after combustion: flue gas losses, wall and door losses, heat carried out with the product and with fixtures and conveyors, and energy spent holding temperature while nothing is being processed.
Typical measures include burner tuning and oxygen trim, recovering flue gas heat to pre-heat combustion air or the charge, repairing refractory and seals, and scheduling batches to cut idle holding time. The savings depend on measured temperatures and flows, not general percentages.
Process cooling and chillers
In the UAE, cooling often carries a larger share of a plant’s electricity than in cooler climates, because ambient heat adds to process heat loads and condenser conditions are harsh for much of the year. Process chillers, cooling towers and chilled water pumping need the same treatment as a building chiller plant: total plant efficiency measured across the real load range, not the chiller’s nameplate rating. Delta T, approach temperatures, staging and setpoints are where the losses show. Our chiller audit covers that measurement in detail.
Process cooling adds one question of its own: whether chilled water is set colder than the process actually requires, which costs efficiency at every hour of operation.
Lighting and HVAC
Lighting and comfort air conditioning in offices, warehouses and control rooms are real costs and simple to fix: LED replacement, occupancy controls, setpoint and schedule corrections. In most plants they are a smaller share than the process utilities above. An audit ranks them on the same payback basis, but should not lead with them.
Measuring savings when production moves
The difficulty with plant energy data is that consumption follows output. A plant that cuts compressed air leaks in a month when production also fell cannot show the saving from the bill alone.
The answer is an energy performance indicator (EnPI) normalised for production: energy per tonne, per unit or per batch, separated by product family where mix matters. A baseline built by regression against production volume, and where relevant against ambient temperature, lets each later period be compared on a like-for-like basis. This is the same discipline an ISO 50001 energy management system requires for its baseline and EnPIs, and the same logic used to prove savings on a performance contract. The Abu Dhabi Measurement and Verification Protocol names production volume as one of the factors that adjustments have to account for, and lists the number and capacity of production lines and product types as examples of static factors that trigger a baseline adjustment when they change. Our piece on the Abu Dhabi M&V Protocol and IPMVP options sets that out.
A saving that cannot be shown against production is a saving that disappears the first time output changes.
Practically, record production at the same interval as energy from the start of the audit. Monthly totals are the minimum; daily or per-shift data makes the model much stronger.
The regulatory hook in Abu Dhabi
An Abu Dhabi plant needs most of this data anyway, for two separate EAD regimes.
Facility-level GHG MRV. EAD’s Industry sector covers physical or chemical transformation of materials into products, including associated on-site combustion, which takes in manufacturing. The system covers Scope 1 emissions, captured as carbon dioxide and methane. Full MRV applies at 25,000 tCO2e of annual Scope 1 emissions. Facilities in covered sectors below the threshold must still submit at least one complete year of data on EAD’s template to confirm their status. Registration and reporting are due by 31 March each year, and third-party verification becomes mandatory from 2027, starting with Reporting Year 2026. Detail is in our article on Abu Dhabi facility MRV.
Annual environmental data reporting. Under Decree No. (1) of 2024 on environmental data reporting, facilities holding an EAD environmental permit report environmental data each year, in the first quarter, including energy and water consumption. Fuel, electricity and water use go on the Annual Resource Consumption template, number 9 of EAD’s ten reporting templates. The report has to be prepared by an EAD-approved environmental consulting office. See EAD’s annual environmental data report.
The practical consequence is that one year of well-metered fuel, electricity, water and production data serves the energy audit, the EAD MRV submission, the annual environmental data report and the corporate inventory. Collected once to a consistent standard, it does four jobs. Our piece on one year of energy data and four obligations and the Abu Dhabi environmental compliance guide set out how they fit together.
Which standard
ISO 50002-1:2025 is the current international standard for energy audits. It replaced ISO 50002:2014, which has been withdrawn, and ISO developed it from ISO 50002:2014 and EN 16247-1:2022. ISO 50002-3:2025, published in June 2025, gives guidance on applying ISO 50002-1 to energy audits of processes, and is used alongside Part 1. Where office or warehouse buildings fall within the audit scope, ISO 50002-2:2025 covers them. An audit carried out inside an ISO 50001 system feeds its energy review directly.
How ESGweise helps
ESGweise carries out energy audits of industrial sites, from metering review and load profiling through to a ranked list of measures with savings, cost, payback and Scope 1 and 2 reductions, and chiller and process cooling audits. We build production-normalised baselines and EnPIs, review M&V plans where measures will be delivered by a contractor or ESCO, implement ISO 50001 so the savings hold, and prepare the energy and emissions data a plant needs for its GHG inventory and verification readiness. We do not sell, finance or install the measures we recommend.
References and sources
- US Department of Energy and Compressed Air Challenge, Improving Compressed Air System Performance: A Sourcebook for Industry, Fact Sheet 4 (Pressure Drop and Controlling System Pressure) and Fact Sheet 7 (Compressed Air System Leaks), May 2026 revision (compressedairchallenge.org)
- IEC 60034-30-1, Rotating electrical machines, Part 30-1: Efficiency classes of line operated AC motors (IE code), edition 2.0, December 2025
- ISO 50002-1:2025, Energy audits, Part 1: General requirements with guidance for use; ISO 50002-3:2025, Energy audits, Part 3: Guidance for conducting an energy audit using ISO 50002-1 in processes
- Abu Dhabi Department of Energy, Abu Dhabi Measurement and Verification Protocol, DoE/PD/P04/005, version 0, effective 2 January 2022
- Environment Agency, Abu Dhabi, Facility-Level MRV portal and Technical Guidance v8, 27 February 2026
- Environment Agency, Abu Dhabi, Self-Monitoring and Reporting Program and Decree No. (1) of 2024 on environmental data reporting
Conclusion
The energy waste in a manufacturing plant is rarely in the production machinery everyone watches. It is in the utilities behind it: air leaking from fittings, pumps throttled against valves, steam passing failed traps, furnaces holding temperature between batches.
An audit that finds it starts from metered data tied to production and expresses every saving per tonne, so that it can still be shown when output changes. In Abu Dhabi, that same data is what EAD asks for.
Frequently asked questions
Which standard covers an energy audit of an industrial plant?
ISO 50002-1:2025 sets the general requirements for energy audits and replaced ISO 50002:2014, which has been withdrawn. ISO developed it from ISO 50002:2014 and EN 16247-1:2022. ISO 50002-3:2025, published in June 2025, gives guidance on applying ISO 50002-1 to energy audits of processes, and is used alongside Part 1 rather than on its own. Where buildings sit inside the audit scope, ISO 50002-2:2025 covers them.
Where does a manufacturing energy audit usually find the biggest savings?
It depends on the process, which is why an audit starts from metered data rather than a checklist. In practice the systems that repay attention first are compressed air, motors and drives on variable loads, steam and condensate systems, furnaces and process heat, and process cooling. Lighting and office HVAC are usually a smaller share of a plant's energy, although the measures there are simple.
Why is energy per tonne better than total energy as a performance indicator?
Because a plant's energy use rises and falls with production. A month with lower total consumption may simply be a month with lower output. An energy performance indicator expressed per unit of product, and adjusted for product mix where that matters, shows whether the plant is actually using energy more efficiently. It is also the basis for proving savings later, since the baseline has to be adjusted for production in the same way.
Does an Abu Dhabi factory have to report its energy use?
Two EAD regimes are relevant. Manufacturing falls in the Industry sector of EAD's facility-level GHG MRV system, which covers Scope 1 emissions with a threshold of 25,000 tCO2e a year, and facilities in covered sectors below the threshold must still file one complete year of data to confirm their status. Separately, permitted facilities report annual fuel, electricity and water consumption to EAD under Decree No. 1 of 2024, on the Annual Resource Consumption template.
How long does an industrial energy audit take?
Most of the time goes into data collection rather than the site visit. Where key systems are not sub-metered, temporary logging has to cover a representative period of production, including shift changes, weekends and product changeovers. A plant with good sub-metering and a production record that can be matched to it can be audited considerably faster than one that relies on the utility bill.