Short answer: on the same mould, a 120 t hybrid with electric injection can use noticeably less power than a hydraulic machine, because its injection draws power mainly while the screw moves and its base load is far lower. In any hybrid vs hydraulic power consumption comparison, the gap depends on which hydraulic machine you mean. A fixed-speed pump leaves the most to save; a servo or variable pump much less. Heaters, chillers and dryers cost about the same on both.
This article explains where the power goes, why datasheet figures mislead, and how to measure the difference on your own job.
Key Takeaways
- An energy guide from ExxonMobil, AMI and Tangram puts a standard hydraulic machine's base load at 75% or more of its energy, against about 10 to 20% for hybrid and all-electric machines.
- Tangram's Robin Kent notes that some new hydraulic machines are not far from all-electric energy use, so compare with the machine you would actually buy.
- Connected load is a nameplate total, not consumption; compare measured kWh per kg on the same mould.
- In Maharashtra, kVAh billing means power factor changes billed units on either type of machine.
Where Does a Hydraulic Machine Use Its Power?
Mostly in the main motor and pump, which Robin Kent of Tangram calls the largest energy users in a hydraulic machine. A fixed-speed pump keeps turning through cooling, mould opening and short stops, so much of its energy heats the oil instead of moving the screw.
The ExxonMobil guide, produced with AMI and Tangram, puts the base load of a standard hydraulic machine at 75% or more of its total energy. Base load is what the machine draws whether or not it makes parts. The guide adds that a high base load can mean the machine is too large for the job.
Kent describes how hydraulic machines have improved over about 20 years, mainly by slowing the motor when oil is not needed or by reducing oil demand. Many older machines with fixed-speed, fixed-volume pumps remain in service with very high energy demand. Retrofits include variable-speed motors, variable-volume pumps and servo motors on fixed pumps.
In a separate PlasticsToday article, Kent recorded one hydraulic machine using 22% less energy with its variable-frequency drive switched on than off. So the hydraulic machine in your comparison may already have closed part of the gap.
What Drives Hybrid vs Hydraulic Power Consumption on One Job?
Three things: which movements are electric, how the hydraulic side is driven, and how much of each cycle is spent cooling or waiting. Electric injection draws power mainly while the screw moves. The hydraulic clamp and ejector still need oil, and the barrel heaters run on both machines.
Where the power goes on a fixed-pump hydraulic machine and on a hybrid with electric injection
| Energy user | Standard hydraulic (fixed pump) | Hybrid (electric injection, hydraulic clamp) |
|---|---|---|
| Injection and screw recovery | Pump-driven; motor runs through the whole cycle | Servo motor draws power mainly while the screw moves |
| Clamp and ejector | Same pump | Hydraulic; draw depends on how its pump is driven |
| Barrel heating | 10 to 25% of a machine's energy input | Same heaters, now the largest part of base load |
| Base load | 75% or more of total energy | About 10 to 20%, mostly barrel heating |
| Chiller, dryer, compressed air | Same on both | Same on both |
Cycles dominated by cooling favour the hybrid most, because a fixed pump spends that time running without moving anything. Short cycles with long injection and recovery leave less to save.
Idle time shows the same effect. Kent has measured idling machines drawing 52% to 97.5% of their full moulding energy, and one idled at 64%. A hydraulic machine drawing 12 kW while moulding would draw about 7.7 kW at that rate while making nothing. He suggests stops longer than about 1.5 hours may be cheaper to switch off and restart.
Heaters are where both machines can save together. The guide notes barrel insulation can cut heating energy by up to 50%.
Why Is Connected Load a Poor Guide to Running Cost?
Connected load adds up the motor and heater ratings, the most a machine could draw at once. What you pay for depends on how hard and how long each part works in your cycle. Two machines with similar connected loads can use very different energy on the same mould.
Measurement settles it. Kent uses a clamp-meter data logger on the supply cables and notes that one machine can be measured in as little as 30 minutes, with heater load averaged over 10 to 15 minutes. He adds that energy rising on the same job can be an early sign of screw or barrel wear.
Monthly value of a lower average draw (20 h a day, 26 days, ₹9.50 per kWh, all assumed)
| Lower average draw | kWh saved per month | Value per month |
|---|---|---|
| 1 kW | 520 | ₹4,940 |
| 2 kW | 1,040 | ₹9,880 |
| 4 kW | 2,080 | ₹19,760 |
The guide also notes that ten years of energy costs more than the machine's purchase price in almost every case. Our view: ask for measured kWh per kg on a mould like yours, and set connected-load comparisons aside.
How Do Maharashtra Tariffs Change the Comparison?
Under MSEDCL's kVAh billing, energy is charged in kVAh and demand in kVA, so a poor power factor raises the bill whichever drive you choose. A lower average draw cuts kVAh, and a corrected power factor cuts both. Use the rates on your latest bill.
MSEDCL's FAQ notes that at a power factor of 0.85, 15% of the power does no useful work, and recommends capacitors or automatic power factor correction panels. It says MERC intended kVAh billing for all HT consumers and for LT consumers above 20 kW from 1 April 2020.
For a comparison, log kVAh as well as kWh on both machines, and check the billing basis printed on your own bill before you put a rupee value on any saving.
What Should You Measure Before Comparing Two Machines?
Run the same mould on each machine for a full shift with a data logger, and record kWh, kVAh, cycle time, good shots, kg processed and idle hours. Divide energy by kg to compare them fairly. See the 120 ton hybrid injection moulding machine page.
Frequently Asked Questions About Hybrid vs Hydraulic Power Consumption
What does total connected load on a datasheet tell me?
It tells you the electrical supply the machine needs, because it adds up motor and heater ratings. It does not tell you consumption, since motors rarely run at full rating and heaters cycle on and off. Use it to size cables and switchgear, and use measured kWh per kg to compare running cost.
Does a hybrid save power on barrel heating?
No. The heaters do the same job on either machine, so barrel heating costs about the same. On a hybrid it becomes a larger share of a smaller total. Insulating the barrel, which the ExxonMobil guide says can cut heating energy by up to 50%, helps on both machine types.
Can a servo retrofit make an old hydraulic machine efficient?
It can reduce consumption a lot, especially on machines with fixed-speed, fixed-volume pumps. Kent lists variable-speed motors, variable-volume pumps and servo motors on fixed pumps as options. Measure the machine first, then compare the retrofit cost and expected saving with the cost of a new machine.
Should a hybrid be switched off during long stops?
For long stops, yes. Even with a low base load, heaters, chillers and compressed air keep drawing power. Kent suggests stops longer than about 1.5 hours may be cheaper to switch off and restart, with an idle mode and heaters set back for shorter breaks.
Do I still need power factor correction with a hybrid?
Check rather than assume. Power factor depends on all the motors, drives and heaters on your supply, not on one machine. MSEDCL recommends capacitors or automatic power factor correction panels where power factor is poor, and under kVAh billing a low figure raises billed units on every machine.
Related Articles
- What Can You Make on a 120 Ton Hybrid Injection Moulding Machine?
- Moulding Precision Gears and Connectors on a 120 Ton Hybrid Machine
- 32 mm or 35 mm Screw on the PH 120: Pressure vs Shot Weight
Sources & References
- ExxonMobil, AMI and Tangram Technology: An Energy Saving Guide for Injection Moulders
- Plastics Engineering (SPE), R. Kent: Energy-Saving Tip 67: Injection Molding: get the right motor (September 2016)
- PlasticsToday, R. Kent: Getting to know your real energy use and cost (January 2010)
- Maharashtra State Electricity Distribution Co. Ltd: kVAh Billing: Frequently Asked Questions
Technical Disclaimer
Disclaimer: The information provided in this document is for general informational and educational purposes only. It is based on technical references and industry information available at the time of preparation and may be subject to change. It does not constitute engineering, technical, commercial or professional advice, nor does it constitute a quotation, specification, warranty or contractual commitment by Pratishna Engineers.
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