Where the Savings Sit by Sector: Semiconductor and Auto-Parts Suppliers

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On the factory floor at semiconductor and auto-parts suppliers, the electricity bill has become a serious problem. It is not simply that rates went up. In both industries the structure of power consumption is fundamentally different from general manufacturing because of how the processes work, and if you manage the site without knowing that difference, anywhere from a few million to a few tens of millions of won leaks away quietly every month. On top of that, the number of suppliers being asked by carmakers and semiconductor customers to demonstrate RE100 compliance as a condition of supply has been rising fast, so managing the electricity bill has become a matter that bears directly on keeping the customer, not just on cutting costs.

Semiconductor plants — 24-hour temperature and humidity control is the heart of the bill

In semiconductor manufacturing, what eats the most power is not the production equipment but the constant temperature and humidity (HVAC) equipment that maintains the cleanroom. A cleanroom has to hold temperature, humidity and particle counts steady 24 hours a day, 365 days a year, so the HVAC equipment does not stop for a single moment.

The problem is that in many plants this HVAC is set to run at the same output at all times, regardless of the outdoor temperature. At night and in winter, when outdoor temperatures are low, the cooling load falls, and if that is not adjusted automatically, unnecessary power keeps being consumed. There are sites that cut HVAC energy substantially simply by switching to inverter control or introducing free cooling with outside air.

Another thing that is easy to miss is compressed air (the compressor). High-pressure nitrogen and air are essential in semiconductor processes, and a compressor consumes power idling even when there is no load. Simply lowering the pressure setpoint at night and during non-operating hours can cut compressor power meaningfully.

Auto-parts plants — peak management and the compressor are the heart of it

Unlike semiconductors, auto-parts plants often have production lines concentrated in the daytime. That structure actually works against you on the electricity bill. When the line starts up between 8 and 9 in the morning and the press, welding and painting equipment all switch on at once, the peak load (maximum demand) shoots up.

The basic charge is set by the peak figure from just a handful of days in the year, and that peak is often captured in the few minutes of simultaneous start-up in the morning. Staggering the start-up order of equipment in 15-minute steps alone can bring the peak down.

The painting process also deserves attention. The temperature control and ventilation equipment in a paint booth use a considerable amount of power, and in many cases they keep running in standby even during hours when no painting is happening. Aligning the production schedule and the paint equipment's running hours precisely can deliver meaningful savings on its own.

The two industries at a glance

Impact · Same manufacturing sector, different places to save

Semiconductor suppliers

No change

HVAC that never stops governs the bill

• Cleanroom temperature and humidity control running 24 hours = the largest power draw
• Fixed output regardless of outside air → waste at night and in winter
• The fix: switch to inverter control and free cooling
• Compressed air idling → lower the pressure during non-operating hours

Auto-parts suppliers

No change

The morning peak decides the basic charge

• Simultaneous line start-up in the morning → peak load spikes
• A few peak days govern the whole year's basic charge
• The fix: stagger the equipment start-up order in 15-minute steps
• Paint booth standby power → align the schedule precisely

Comparing the two industries' main loads and saving levers in a table gives the following.

Common to both — three things to check now

All three items below apply to both industries, but we cover only why they are a particular problem in these industries. The general principles behind each (contract power, power factor, the structure of the basic charge) are left to the related columns.

• Are you being asked about RE100? — Carmakers and semiconductor customers have already begun requiring a renewable energy transition across the whole supply chain, and the share of renewable energy is increasingly included in supplier ESG assessments. Even if you are not being asked now, there is a strong chance it will arrive as a condition of supply within one to two years.
• Does your contract power match your actual usage pattern? — In both industries it is easy to leave contract power untouched after adding equipment or changing a line. Auto parts in particular sees large swings in utilisation depending on the volumes the customer orders, so contract power set high on the basis of maximum operation is still billed as a basic charge in the off-season.
• Is your power factor being managed? — Auto parts, with its many presses, welders and large motors, and semiconductors, with their high-capacity HVAC, are both environments where the power factor easily falls. If the power factor on your bill is 90% or below, a surcharge is being added every month.

How much can you actually cut

The following is an assumption-based example to aid understanding. Actual savings vary considerably with the industry, the size of the plant and how it is operated.

There are a fair number of sites with room to cut 10-20% off the monthly electricity bill through improved operating practice alone, with no capital investment. Design a renewable energy transition (PPA, RECs and so on) on top of that and you get RE100 compliance and a fixed long-term power price at the same time, which makes it a strategy that reduces exposure to rate movements while also meeting your customer's conditions of supply.

In summary

The electricity bill at a semiconductor or auto-parts plant has a more complex structure than in general manufacturing. Without knowing how the process works, you will waste time and money poking at the wrong things.

• Semiconductors — HVAC running 24 hours is the largest power draw. Outside-air-linked control and compressed air management come first.
• Auto parts — The morning peak decides the basic charge. Staggering the start-up order and aligning the paint schedule come first.
• Both — RE100 requirements, whether contract power is appropriate, and the power factor: check these three first whatever the industry.

An accurate diagnosis comes first. The general saving methods and the principles behind the tariff structure continue in the related columns below.

• [Source: Corporate Energy Transition Center — analysis based on the director's on-site consulting experience]
• [Source: KEPCO industrial electricity tariffs and the power factor charge]
• [Source: Korea Energy Agency — K-RE100 scheme guide]

Note: The saving rates and amounts in the text (10-20%, KRW 3.6-12 million a year and so on) are assumption-based examples drawn from field experience, and the actual figures vary with the industry, the size of the plant, how it is operated and the contract terms. An on-site diagnosis is needed before you act.