# Hot Runner vs Cold Runner Payback Calculator

> Source: https://netray.co/tools/hot-runner-vs-cold-runner-payback-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Work out whether the extra cost of a hot runner system pays back through saved resin and shorter cycles, with a sweep over annual shot volume.

## Category

cost-finance

## Industry

Plastics

## Audience

- Mold buyer
- Process engineer
- Plastics estimator

## Tool

**Kind:** calculator

**Currency:** $

**Inputs:**

#### Extra mold cost for hot runner

**Key:** extra_cost

**Type:** number

**Default:** 18000

**Min:** 0

**Step:** 500

**Unit:** $

**Help:** Hot runner system, controller and added mold work minus the cold runner cost it replaces.

#### Cold runner weight per shot

**Key:** runner_g

**Type:** number

**Default:** 14

**Min:** 0

**Step:** 0.5

**Unit:** g

**Help:** Sprue plus runner plus any cold slugs, not the parts.

#### Resin price

**Key:** resin_price

**Type:** number

**Default:** 2.8

**Min:** 0

**Step:** 0.05

**Unit:** $/kg

#### Value recovered from regrind

**Key:** regrind_credit

**Type:** slider

**Default:** 40

**Min:** 0

**Max:** 100

**Step:** 5

**Unit:** %

**Help:** Share of resin value you recover by regrinding and reusing the runner. Zero if it is scrapped.

#### Annual shots

**Key:** annual_shots

**Type:** number

**Default:** 400000

**Min:** 0

**Step:** 10000

**Unit:** shots

#### Cycle time saved with hot runner

**Key:** cycle_save

**Type:** number

**Default:** 1.5

**Min:** 0

**Step:** 0.1

**Unit:** s

**Help:** Often from shorter runner cooling and no runner ejection. Zero if cooling of the part sets the cycle.

#### Machine hourly rate

**Key:** machine_rate

**Type:** number

**Default:** 55

**Min:** 0

**Step:** 1

**Unit:** $/hr

**Outputs:**

#### Net material saving per shot

**Key:** mat_shot

**Expr:** runner_g / 1000 * resin_price * (1 - regrind_credit / 100)

**Format:** decimal

**Description:** Dollars per shot after regrind value.

#### Annual material saving

**Key:** mat_year

**Expr:** mat_shot * annual_shots

**Format:** currency

**Primary:** true

#### Annual machine time saving

**Key:** cycle_year

**Expr:** annual_shots * cycle_save / 3600 * machine_rate

**Format:** currency

**Description:** Real only if the machine hours are constrained or can be sold.

#### Total annual saving

**Key:** total_year

**Expr:** mat_year + cycle_year

**Format:** currency

**Primary:** true

#### Payback period

**Key:** payback_mo

**Expr:** if(gt(total_year, 0), extra_cost / (total_year / 12), 0)

**Format:** months

**Description:** Zero means no payback because there is no saving.

#### Net benefit over 5 years

**Key:** net5

**Expr:** total_year * 5 - extra_cost

**Format:** currency

**Chart:**

#### Net 5 year benefit vs annual shots

**Type:** line

**X:** annual_shots

**From:** 50000

**To:** 1000000

**Steps:** 20

**Series:**

- net5

**Disclaimer:** Excludes hot runner maintenance, color change scrap, higher startup scrap and heater failures. Add those costs to the extra mold cost for a fuller view.

## Content

**Intro:** A hot runner removes the sprue and runner from every shot, but it costs real money up front. This calculator compares the extra tool cost against saved resin and shorter cycles so the purchase can be justified, or rejected, with numbers.

**Sections:**

#### How to use it

**Body:** Enter the extra cost of the hot runner mold over a cold runner version, the weight of sprue and runner per shot, resin price, and how much of the runner value you recover by regrinding. Then enter annual shots and any cycle time reduction. The payback is the extra cost divided by monthly saving. The chart shows how the five-year benefit changes with volume, which is usually the deciding factor.

#### Method behind the numbers

**Body:** Material saving per shot is runner weight times resin price times the share of value lost. If you regrind and reuse half the runner at full value, you only lose the cost of grinding and the risk of quality drift, so enter a high recovery. Machine time saving is shots times seconds saved, converted to hours and priced at the machine rate. It is only a cash saving if that time can be used for other jobs or avoids overtime.

**Bullets:**

- Low volume and cheap resin favor cold runner
- Expensive resin, large runners and high volume favor hot runner
- Engineering resins that cannot be reground favor hot runner strongly

#### Worked example

**Body:** A 14 g runner at $2.80 per kg with 40 percent value recovered wastes about $0.0235 per shot. At 400,000 shots that is roughly $9,400 a year. A 1.5 second cycle saving at $55 per hour adds about $9,200. Total near $18,600 a year against $18,000 extra cost gives a payback of about 12 months.

#### Common mistakes

**Body:** Counting the full resin price when regrind is reused, claiming cycle savings that do not exist because part cooling is the limit, and leaving out hot runner running costs such as nozzle tips, heater replacements and slower color changes. Quality also matters: sprue vestige, gate type and thermal degradation in the manifold can decide the choice regardless of payback.

**Cta:** Netray can read your ERP job history to show real shot volumes and scrap by mold, so a hot runner decision rests on actual runner waste rather than estimates.

**Faq:**

#### When does a hot runner not make sense?

**Answer:** For low volume, short runs, frequent color changes or small runners with cheap resin, the extra cost and maintenance can outweigh savings. Cold runners are also easier to troubleshoot and cheaper to modify.

#### Does a hot runner always shorten the cycle?

**Answer:** No. It removes runner cooling and ejection as limits, but if the part wall cooling already sets the cycle, the saving is near zero. Enter zero seconds in that case and judge on material and quality.

#### How much runner can I regrind?

**Answer:** It depends on the resin, the part requirements and customer specifications. Many parts allow a limited percentage of regrind, and some regulated or optical parts allow none. Enter the value you can actually recover.

#### What other costs should I include?

**Answer:** Controller, spare tips and heaters, extra startup scrap, longer color changes, and the added mold maintenance labor. Add them to the extra cost field or reduce the saving to be realistic.

## Search terms

hot runner vs cold runner, hot runner payback calculator, hot runner cost justification, cold runner waste cost, runner scrap cost calculator, hot runner roi, is a hot runner worth it

---
Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json