Energy guide
Specific energy consumption: is your energy buying production?
The electricity bill tells you how much energy the plant used. It does not tell you whether that energy was well spent. Specific energy consumption does: energy per unit of what you make. When it rises with output flat, something is wasting power.
What SEC is
Specific energy consumption (SEC) is the energy used divided by the production made in the same period:
SEC = energy used (kWh) ÷ production (kg, tonnes, metres, pieces)
A spinning mill that used 1,20,000 kWh to make 20,000 kg of yarn in a week ran at 6 kWh per kg. If next week it makes the same yarn at 6.6 kWh per kg, it spent 10% more energy for the same output, even if the bill looks normal because production was lower.
The right unit for your industry
Use the unit your plant already counts production in, and keep it the same every time.
| Industry | Common SEC unit | What moves it most |
|---|---|---|
| Spinning | kWh per kg of yarn | Yarn count, spindle speed, humidification and compressed air |
| Weaving and processing | kWh per metre or per kg of fabric | Loom type and speed, dryers, stenters and boilers |
| Rice mill | kWh per tonne of paddy | Huller and polisher loading, idle running between batches |
| Cold storage | kWh per tonne stored, per day or month | Fill level, door openings, condenser cleanliness, ambient temperature |
| Foundry and induction furnace | kWh per tonne of liquid metal | Charge mix, lid-open time, holding time and lining condition |
| Plastics and moulding | kWh per kg processed | Heater bands, hydraulic idling, cycle time and chiller load |
| Hotels | kWh per occupied room-night | Occupancy, air-conditioning set points, laundry and kitchen timing |
| Hospitals | kWh per occupied bed-day | Air-conditioning, operating theatres and imaging hours |
What counts as a good SEC depends on the product, the machinery and the process, so a figure from another plant is a weak guide. The most useful benchmark is your own plant’s SEC on its best normal days.
Mistakes that make SEC misleading
- Ignoring base load. Lighting, compressors and utilities run whatever the output. On a slow day the same base load is spread over fewer units, so SEC rises without any machine getting worse. Compare days with similar output, or track base load separately.
- Mixing products. A coarse count and a fine count, or a light and a heavy casting, have very different SEC. Compare like with like, or track SEC per product line.
- Changing the boundary. If the energy figure includes the office and colony one month and not the next, SEC moves for no real reason. Fix which meters count.
- Monthly only. A monthly figure hides the bad shifts inside the good ones. A daily SEC shows which day went wrong while people still remember why.
- kWh or kVAh. SEC is normally worked out in kWh. If your bill is in kVAh, the cost per unit of production also carries power factor, so look at both. See kVAh billing.
Using SEC to find waste
- Plot daily SEC against daily output. Days above the usual band are where to look.
- Split energy by panel. If one panel’s energy rises while output is flat, the problem is on that panel. See sub-metering.
- Check what runs when nothing is being made. Idle machines raise SEC on every day. See machine running and idle tracking.
- Before and after any upgrade, compare SEC, not just the bill. A higher bill with more output can still be a saving.
SEC and energy-efficiency schemes
Savings are usually measured as a change in SEC against a baseline, not as a smaller bill. The ADEETIE scheme for MSMEs establishes a baseline specific energy consumption for each beneficiary and checks savings against it. An energy auditor will ask for the same production and energy records. See energy audit.
How KONDUKTOR® EMS tracks SEC
- Enter production every day on the dashboard, or upload many days at once from a CSV file.
- The dashboard works out plant-wide SEC for each day in kWh per unit, from the meter energy for that day.
- The SEC table downloads as a CSV file, with date, units produced, energy and SEC.
- Energy per panel, per hour and per shift, to find which part of the plant moved the number.
Common questions
How do you calculate specific energy consumption?+
Divide the energy used in a period by the production made in the same period, for example kWh per kg of yarn or kWh per tonne of paddy. Use the same meters and the same production unit every time so the figures can be compared.
What is a good SEC for my industry?+
It depends on the product, the machinery and the process, so figures from other plants are only a rough guide. The most useful benchmark is your own plant’s SEC on its best normal days, compared day by day for similar output and product mix.
Why does SEC go up when production falls?+
Part of the plant’s load runs whatever the output: lighting, compressors, utilities and idle machines. On a slow day that fixed energy is spread over fewer units, so SEC rises even if no machine has got worse.
Should SEC be in kWh or kVAh?+
SEC is normally worked out in kWh, the real energy used. If your connection is billed in kVAh, the cost per unit of production also includes the effect of power factor, so it is worth looking at both.
Energy per unit, every day.
Book a live demo and see daily SEC worked out from your own meters and production figures.