# How much electricity and CO2 does a servo injection moulding machine save over a fixed-pump hydraulic one?

Canonical: https://senseible.earth/answers/servo-vs-hydraulic-injection-moulding-energy

There is no fixed figure; it depends on your cycle. Measure kWh per kg of good parts on the same mould for a week on each machine, take the difference, multiply by annual output, then by 0.710 kg CO2 per kWh. Savings are biggest on long cycles with long cooling or holding times.

## Where the saving comes from

A fixed pump hydraulic machine runs its motor at full speed through the whole cycle. When the cycle needs little oil, during cooling, holding or mould open, the surplus goes over a relief valve and turns into heat. A servo pump slows down or stops when demand drops, so it draws power only for the work done, and the oil cooler needs less water.

The barrel heater bands are a separate load. A servo pump does not change them, so heater kWh stay about the same.

## How to measure it fairly

EUROMAP 60.1 rates machines on a standard test cycle, which helps when comparing quotes. EUROMAP 60.2 measures kWh per kg on a real part, which is the test above. Decide on your own mould data.

1. Fit a kWh meter on the machine supply, covering motor and heaters, or on the motor alone if you only compare pumps.
2. Run the same mould, material and cycle time on both machines, or before and after a servo retrofit.
3. Log kWh and the weight of good parts for at least a week each, so start ups and rejects are included.
4. Specific energy = kWh divided by kg of good parts. Compare the two figures.

## When a servo pays back and when it does not

- Strong case: long cooling or holding times, thick walled parts, machines running two or three shifts.
- Weak case: fast thin walled cycles where the pump is busy most of the time, or machines that run a few hours a day.
- Payback = retrofit or price difference divided by (kWh saved a year x your energy charge per kWh). Count demand charges only if the change also lets you lower your contract demand.

## Be careful with brochure percentages

Machine makers quote savings measured on cycles that suit their machine. Do not put a brochure percentage in a carbon report or a loan application. Use your measured before and after kWh per kg, and keep the meter logs and production records together.

## Worked example: one 250 t machine, measured figures

- Hydraulic: 0.90 kWh per kg good parts; servo: 0.55 kWh per kg (one week each, same mould)
- Saving: 0.35 kWh per kg x 3,00,000 kg a year = 1,05,000 kWh
- CO2: 1,05,000 x 0.710 = 74,550 kg, about 74.6 t a year
- Money at Rs 8 per kWh: 1,05,000 x 8 = Rs 8,40,000 a year
- Payback on a Rs 6 lakh retrofit: 6,00,000 / 8,40,000 x 12 = about 8.6 months

The kWh per kg, output, tariff and retrofit price are illustrative. Use your own measurements.

## What Senseible does here

Senseible reads your electricity bills into a monthly record of kWh and CO2 at 0.710 kg per kWh, so the drop after a retrofit shows in the plant total. Machine level meter feeds are set up with the Senseible team for each customer.

- [Injection moulding footprint per kg](https://senseible.earth/answers/injection-moulding-carbon-footprint-per-kg)
- [Measure savings from an efficiency project](https://senseible.earth/answers/how-to-measure-savings-from-energy-efficiency-project)
- [Energy transition savings calculator](https://senseible.earth/calculators/energy-transition-savings)
- [VFD savings on pumps and fans](https://senseible.earth/answers/vfd-pump-fan-energy-co2-savings)

Sources: [BEE SME programme, cluster energy profiles for plastics processing (beeindia.gov.in)](https://beeindia.gov.in), [CEA CO2 Baseline Database, version 21.0](https://cea.nic.in/cdm-co2-baseline-database/?lang=en)

Last reviewed 2026-10-18.