Is cable loss the same as voltage drop?

No. Voltage drop answers volts and percent drop. Cable loss answers watts, annual kWh and cost handoff from conductor resistance.

Does this calculator select a larger cable?

No. It can show the operating-loss effect of entered cable data, but cable selection still needs current capacity, voltage drop, protection and installation review.

Why does single phase use a factor of two?

The worksheet applies two current-carrying conductors for the single-phase loss loop when resistance is entered as a single-conductor value.

Why does three phase use a factor of three?

For a balanced three-phase worksheet, loss is estimated across three current-carrying conductors.

Does the annual cost match the power bill?

No. It is a simple handoff from entered hours and c/kWh. It excludes fixed charges, demand charges, time bands, GST treatment and retailer plan rules.

Cable loss calculator

Rroute = Rkm x Lkm; Ploss = F x I^2 x Rroute; Eannual = Ploss x Hannual / 1000; Cannual = Eannual x tariff_c_per_kWh / 100

Single-phase loss uses two current-carrying conductors and balanced three-phase loss uses three.
Resistance is entered as a single-conductor value in ohm/km.
Annual energy is a handoff from entered operating hours.
Annual cost uses the entered c/kWh value and does not compare retailer plans.

Formula variables
Variable	Meaning	Unit	Use
Rkm	Conductor resistance	ohm/km	Single-conductor resistance entered from the project cable data source.
Lkm	One-way route length	km	Route length converted from metres.
Rroute	Route resistance	ohm	Single-conductor resistance over the entered one-way route.
F	Loss phase factor	factor	Two for single phase and three for balanced three phase.
I	Current	A	Current used for the cable-loss estimate.
Ploss	Cable loss	W	Calculated watt loss in the cable conductors.
Hannual	Annual operating hours	h/year	Entered hours where the loss basis is expected to apply.
Eannual	Annual energy loss	kWh/year	Cable loss multiplied by annual hours.
tariff_c_per_kWh	Tariff entered	c/kWh	User-entered energy rate for the cost handoff.
Cannual	Annual cost	AUD/year	Annual energy loss multiplied by entered tariff and divided by 100.

Cable loss calculator technical guide

Estimate Australian cable loss from entered current, route length, conductor resistance, operating hours and tariff values.

Use this calculator when a cable run already has a current, route length and conductor resistance basis, and the reviewer wants to see the watts lost in the cable and the annual kWh or cost handoff. Typical uses include comparing route options, checking a long feeder, documenting an operating-cost assumption or explaining why voltage-drop and energy-loss questions are related but not identical.

The page is deliberately narrow. It estimates cable conductor loss, annual energy loss and cost from entered values. It does not select a cable, confirm current capacity, calculate voltage drop, compare retailer plans, model a complete bill or decide installation compliance.

Field use cases

Practical cable loss use cases
Work setting	Real question	Useful action from this page
Long final circuit	How many watts are lost in this cable run?	Enter current, length and resistance to record loss separately from voltage drop.
Mechanical plant run	What annual kWh is lost if this load runs many hours?	Add annual operating hours and tariff to create a cost handoff.
Route comparison	Does a shorter route materially reduce loss?	Compare two route lengths with the same current and resistance basis.
Candidate cable review	Does a lower-resistance candidate reduce annual operating cost?	Enter the alternate resistance and compare the annual kWh result.
Estimating note	What value should be carried into an operating-cost discussion?	Export loss watts, annual kWh and entered tariff together.

A useful record is specific. "Cable loss checked" is weak. "LOSS-RUN-1, single phase, 32 A, 40 m, 1.15 ohm/km, 1800 h/year and 32 c/kWh gives 94.21 W loss and 169.57 kWh/year" can be checked when the current, route or conductor data changes.

Cable loss checklist

Values to collect before using the worksheet
Value	Where it normally comes from	Why it matters
Loss reference	Cable schedule, board record, drawing or estimating note	Ties the estimate to a cable run.
Current	Load calculation, nameplate data, design current or measured basis	Loss rises with current squared.
Route length	Cable route takeoff or site measurement	Sets the conductor resistance over the route.
Conductor resistance	Cable schedule, datasheet, manufacturer data or project source	Determines watts lost without reproducing cable tables.
Annual operating hours	Usage schedule, production plan or estimating assumption	Converts watts into kWh per year.
Tariff	Project, bill, retailer plan or estimating assumption	Converts annual kWh into an annual cost handoff.

The calculator is most useful when resistance comes from the same cable context being reviewed. A resistance value from another conductor size, material or temperature basis can produce a misleading loss estimate.

Method comparison matrix

Cable loss method basis
Method element	What the calculator does	Best use	Main risk
Route resistance	Multiplies entered ohm/km by one-way route length in kilometres.	Building a transparent loss record from cable data.	Using a resistance value from the wrong source.
Phase factor	Applies two conductors for single phase and three for balanced three phase.	Simple cable-loss comparison.	Using the balanced three-phase assumption when the load is not balanced.
Current squared	Applies I squared to route resistance and phase factor.	Showing why current has a large effect on loss.	Treating a rough current as a final design value.
Annual hours	Converts watts into annual kWh.	Operating-cost handoff and scenario comparison.	Using hours that do not match actual operation.
Tariff handoff	Converts annual kWh into entered annual cost.	Estimating and discussion notes.	Treating a simple c/kWh value as a full bill model.

The method is intentionally transparent so another reviewer can repeat it. It should sit beside voltage drop, cable-size screening and energy-cost records, not replace them.

Worked records

Cable loss examples
Situation	Inputs	Result	Record use
Single-phase final circuit	32 A, 40 m, 1.15 ohm/km, 1800 h/year, 32 c/kWh	94.21 W, 169.57 kWh/year, 54.26 AUD/year	Record operating loss separately from voltage drop.
Three-phase mechanical run	42.45 A, 60 m, 1.15 ohm/km, 1800 h/year, 32 c/kWh	373.01 W, 671.43 kWh/year, 214.86 AUD/year	Shows why annual loss matters for long-running plant.
High-use feeder review	75 A, 80 m, 0.85 ohm/km, 2400 h/year, 38 c/kWh	1147.50 W, 2754.00 kWh/year, 1046.52 AUD/year	Triggers review of current basis, cable data, route length and alternatives.

These examples show why cable loss can matter even when voltage drop is being checked separately. Voltage drop controls voltage delivered to the load. Cable loss controls watts and energy that become heat in the conductors.

Review workflow

Identify the cable run, circuit, board or estimating line being checked.
Confirm the current used for the loss estimate.
Enter the one-way route length from the cable takeoff or site route.
Enter conductor resistance from the project cable data source.
Choose single phase or three phase to set the loss factor.
Enter annual operating hours where this current and resistance basis is expected to apply.
Enter the c/kWh value used for the cost handoff.
Read cable loss, annual kWh and annual cost together.
If the annual kWh or cost is high, review current basis, route, resistance source and candidate alternatives before using the result.
Export the record only when the source values and operating assumptions are clear.

This workflow keeps the loss estimate in its proper role. It helps quantify energy lost in the conductors, but it does not create a cable selection or tariff decision.

Boundary with voltage drop and energy cost

Where this calculator stops
Related task	Use this page?	Why
Voltage drop in volts or percent	No	Use the voltage drop calculator when the question is delivered voltage.
Cable size screening	No	Use cable size when current capacity and voltage-drop margin are being reviewed.
Load running cost	No	Use energy cost when the whole load kWh and tariff question is the task.
Retailer plan comparison	No	This page uses one entered c/kWh value and does not model plan features.
Heat, grouping or installation compliance	No	These need project, manufacturer and standards-context review.

Keeping the boundary clear prevents a loss worksheet from becoming a cable selection or bill model. This page answers one question: what conductor loss follows from the entered current, resistance and route basis.

Australian context

Australian cable-loss planning normally happens beside cable schedules, project specifications, manufacturer data, installation conditions and operating-cost assumptions. A public calculator can help make the arithmetic visible, but it cannot know the final cable size, conductor temperature, load profile, tariff structure, retailer plan or installation compliance outcome.

This calculator does not reproduce cable resistance tables or retailer tariff feeds. It records the result from values entered by the user so the estimate can be reviewed beside voltage-drop, cable-size and energy-cost records.

Minimum export record

Cable loss export record
Record item	Why it matters
Loss reference	Ties the estimate to a cable run or estimating line.
Supply arrangement	Shows whether the loss factor is single phase or three phase.
Current and route length	Defines the operating and geometry basis.
Conductor resistance	Records the cable data used.
Annual hours	Shows how watts were converted to kWh.
Tariff	Shows the manual cost handoff value.
Reviewer	Identifies who prepared or checked the estimate.

Stop points

Current is a rough allowance with no design or measured basis.
Route length excludes risers, deviations or actual installation path.
Conductor resistance comes from a different cable size, material or condition.
Annual hours are guessed without a usage basis.
Tariff is copied from another site or billing class.
The result is being used to select cable size without voltage drop and current-capacity review.
The annual cost is being treated as a full bill or retailer-plan comparison.
The estimate is being used as installation approval or compliance confirmation.

The useful output is a repeatable cable-loss record, not a final cable or billing decision. Keep current, route length, resistance, annual hours and tariff together so the result can be checked when the project basis changes.

Loss reference: LOSS-RUN-1
Supply arrangement: Single phase
Current: 32 A
Route length: 40 m
Conductor resistance: 1.15 ohm/km
Annual hours: 1800 h
Tariff: 32 c/kWh

Route resistance0.046 ohm over the entered one-way route.
Loss factor2 current-carrying conductors are used for single phase loss.
Annual loss169.57 kWh from cable loss across the entered operating hours.

Cable loss94.21 W

54.26 AUD/year at the entered tariff.

The cable loss is modest but visible enough to record where the operating hours and tariff assumption matter to the project estimate.

Single-phase loss applies two current-carrying conductors in the loop.
Resistance is entered from the project cable data source.
Tariff is entered manually and is not a retailer-plan comparison.

Loss reference: MECH-LOSS-1
Supply arrangement: Three phase
Current: 42.45 A
Route length: 60 m
Conductor resistance: 1.15 ohm/km
Annual hours: 1800 h
Tariff: 32 c/kWh

Route resistance0.069 ohm over the entered one-way route.
Loss factor3 current-carrying conductors are used for three phase loss.
Annual loss671.43 kWh from cable loss across the entered operating hours.

Cable loss373.01 W

214.86 AUD/year at the entered tariff.

The three-phase loss is higher because the worksheet applies three current-carrying conductors, so the annual kWh handoff becomes useful for operating-cost discussion.

The three-phase load is treated as balanced for this worksheet.
The entered current is already the line current used by the project record.
Cable size selection and voltage drop are checked separately.

Loss reference: FEEDER-LOSS-1
Supply arrangement: Three phase
Current: 75 A
Route length: 80 m
Conductor resistance: 0.85 ohm/km
Annual hours: 2400 h
Tariff: 38 c/kWh

Route resistance0.068 ohm over the entered one-way route.
Loss factor3 current-carrying conductors are used for three phase loss.
Annual loss2754 kWh from cable loss across the entered operating hours.

Cable loss1147.5 W

1046.52 AUD/year at the entered tariff.

The annual energy loss and cost are high enough to trigger review of the cable data, current basis, route length, operating hours and candidate alternatives.

The result is an operating-loss estimate, not a cable-size decision.
The tariff is an entered project value.
The review threshold is a worksheet flag, not a compliance rule.