Published 4 min readTechnical guide
Calculate all-electric blow molding payback from the additional installed investment and the annual net operating savings for accepted bottles. A meaningful comparison uses the same product requirements, an explicit equipment boundary and measured or clearly stated assumptions for energy, resin, output and maintenance.
The drive technology is one part of the calculation. Start with a comparable production requirement, then compare the cost of making bottles that pass inspection.
Set a comparable production baseline
Record the bottle drawing, resin, target weight, mold, annual accepted quantity and operating schedule for both options. Include installation, utility changes, tooling compatibility and the downstream equipment required to reach that quantity.
Use metered electricity per 1,000 accepted bottles where possible. Define whether the meter covers only the machine or also chillers, compressors, granulators and inspection equipment. A lower machine-meter reading may not represent the same reduction across the complete line.
Tongda’s all-electric personal-care bottle case provides a concrete application for discussing output and weight control. Its figures are not a substitute for measurements on the bottle being quoted.
Calculate energy savings with units attached
Annual electricity saving = (baseline kWh − proposed kWh per 1,000 accepted bottles) × annual accepted bottles ÷ 1,000 × electricity price per kWh.
Use an electricity tariff appropriate to the factory and account for relevant demand charges separately. Keep the currency and price date consistent across the investment comparison.
The following example uses hypothetical inputs to demonstrate the arithmetic. It is not a Tongda quotation or a measured saving from the HSEII-12L/8 case.
| Example input | Assumption |
|---|---|
| Annual accepted production | 8,000,000 bottles |
| Baseline measured energy | 25 kWh per 1,000 accepted bottles |
| Proposed measured energy | 18 kWh per 1,000 accepted bottles |
| Electricity price | USD 0.15/kWh |
| Other annual net operating savings | USD 1,600 |
| Additional installed investment | USD 30,000 |
The energy difference is 7 kWh per 1,000 bottles. At 8 million accepted bottles, that is 56,000 kWh/year, worth USD 8,400/year. Adding USD 1,600 of other net savings gives USD 10,000/year, so the simple payback is 3 years.
Separate average weight from weight tolerance
A bottle specified as 36 g ± 2 g does not necessarily use less resin on average than one specified as 36 g ± 3 g. Both may have a mean of 36 g. Better repeatability can support a safe target adjustment, but the actual mean reduction must be demonstrated while quality requirements remain satisfied.
Annual net resin saving in tonnes = measured mean-weight reduction in grams × annual accepted bottles ÷ 1,000,000.
At the example’s 8 million bottles, a demonstrated 1 g reduction would equal 8 tonnes of net bottle material per year. This is a separate scenario, not a saving already included in the energy example. Material purchases also depend on flash, rejects, regrind use and material losses; do not treat all recovered scrap as avoided virgin-resin purchasing.
Include maintenance, setup and downtime
All-electric actuation changes the drive and maintenance requirements. It can remove the associated hydraulic-drive oil circuit, while mechanical lubrication and auxiliaries remain.
Compare planned service, spare parts, operator time, changeovers and downtime using a defined annual basis. Include additional software, service or financing costs where applicable. Only claim downtime savings when there is a reasonable baseline and a clear way to measure the improvement.
If accepted annual output already includes rejects and stoppages, do not subtract those losses a second time. Also avoid assigning both higher accepted output and a second overlapping downtime saving to the same improvement.
Test the payback against lower utilization
Simple payback is a screening measure, not a full investment appraisal. It does not account for the time value of money, tax treatment or the residual value of the equipment.
Annual net savings are shown in USD, with simple payback in years.
| Bottles/year | Net/year | Years |
|---|---|---|
| 8,000,000 | 10,000 | 3.00 |
| 6,000,000 | 7,900 | 3.80 |
| 4,000,000 | 5,800 | 5.17 |
The sensitivity table uses the same USD 30,000 additional investment. It holds the 7 kWh-per-1,000-bottle energy difference, USD 0.15/kWh tariff and USD 1,600 other annual net saving constant to isolate the effect of output. In a factory model, reconsider which maintenance and operating costs change with utilization.
Questions buyers ask
Does all-electric drive always give a three-year payback?
No. Three years is the result of the hypothetical inputs above. Different bottle quantities, electricity tariffs, installed costs and measured efficiencies produce different results.
Should I compare machine power ratings?
Power ratings help plan the electrical supply. Operating cost requires measured energy over comparable production runs and a consistent equipment boundary.
Which figures should appear in a supplier comparison?
Use accepted output, metered kWh, average bottle weight and variation, rejects, utility conditions, annual operating time and the full installed-cost scope. Keep theoretical ratings separate from test results.
Build a comparison for your bottle
Compare the fully electric series with a configuration suited to your product. Send your bottle drawing, resin, annual accepted quantity, electricity tariff and existing-line measurements to request a project-specific comparison. For another drive arrangement, read the EH800A hybrid-drive case.