AGL Cable Power Loss Calculator | Precision AGL Academy

Cable Power Loss

I²R heat loss along a primary AGL cable run, at each brightness step and over a year of operation.

About this calculator

The cable loses power as heat in proportion to the square of the series current, so it falls steeply at lower brightness steps. Add each cable section, choose the brightness steps and how long the circuit spends on each, and the tool reports the loss in watts, the heat per metre, the share of the load, and the yearly energy.

Cable Sections

Length entered as

Length unit

Section / description	Conductor	Length (m)	Loss at full (W)

Conductor temperature (°C)

Copper resistance rises about 0.393 % per °C above 20 °C.

Custom conductor (Ω/km at 20 °C)

Rule note

Used by any section set to "Custom". Take it from your cable data sheet.

Brightness Steps & Operating Time

Step preset

Check step currents against your CCR data sheet.

Operating hours per year

Rule note

Hours the circuit is energised, on any step. The 4,000 h shown is a placeholder; use your own airfield operating profile.

Step	Current (A)	Share of hours (%)

The shares are placeholders. Replace them with your own operating profile.

Circuit real load at full brightness (kW) (optional)

Rule note

For example from Calculator #13. Real power of the lamps and transformers, not including the cable loss. Used to show the cable loss as a share of the load. Leave 0 to skip.

Energy price per kWh (optional)

Any currency. Leave 0 to skip the cost.

Report details

Project Name (for report)

Circuit ID (for report)

Loss by Brightness Step

Step	Current (A)	Loss (W)	Of full-brightness loss	Hours / year	Energy (kWh)

Build-up

Loop resistance

—

Heat per metre

—

Loss ÷ loop length, i.e. per metre of conductor at full brightness. Per metre of route it is double where both legs share a trench.

Loss as share of load

—

Needs a real load

Average loss

—

Weighted by operating time

Energy per year

—

Cost per year

—

Needs an energy price

Conductor Comparison

The whole loop length re-run in a single conductor size, with the same steps and hours. The last column is the change against the design above.

Conductor	Loop resistance (Ω)	Loss at full (W)	Energy (kWh / yr)	Change vs design

Calculator #22 | Rev. 1.2 | 26 Oct 2026

Engineering reference tool. Final design shall be verified against the cable manufacturer's data and the applicable project specification.

Method & Reference

How the loss is calculated

Every step is shown so the result can be checked by hand.

1. Loop resistance

Each section's resistance comes from the conductor's nominal Ω/km at 20 °C, corrected for temperature, then the sections are added.

R = Σ ρ₂₀ × [1 + 0.00393 × (T − 20)] × L ÷ 1000

2. Loss at each step

The same current flows through the whole series loop, so each section's loss adds directly.

P = I² × R

Halving the current cuts the loss to a quarter, so the lower steps lose much less than full brightness.

3. Yearly energy and cost

E = Σ P × (hours × share) ÷ 1000 Cost = E × price

Hours on each step are the operating hours multiplied by that step's share.

4. Share of load and heat per metre

Share = P_full ÷ (real load × 1000) × 100 Heat = P_full ÷ L

Worked example

Item	Value
#8 AWG, 3,000 m loop, 20 °C	R = 6.306 Ω
Loss at 6.6 A	274.7 W
Loss at 5.2 A	170.5 W
Loss at 2.8 A	49.4 W
Heat per metre at 6.6 A	0.092 W/m
Share of a 5 kW load	5.49 %
Energy, 4,000 h at default shares	440.5 kWh

What this tool does not do

It does not calculate voltage drop (see Calculator #15), include the isolating transformer or fixture losses, connectors, splices or reactance, or cover aluminium conductors. Resistance values are nominal DC figures, so confirm them against your cable data sheet. AWG sizes use nominal stranded-copper values at 20 °C (ASTM B3/B8 basis, about 2 % above the ideal-copper figures); metric sizes use the IEC 60228 Class 2 maximum.

Cable Power Loss Calculator: Frequently Asked Questions

Quick answers on I squared R heat loss along a primary AGL cable run.

What does the Cable Power Loss calculator do?

It calculates the I squared R heat loss along a primary AGL cable run, at each brightness step and over a year of operation. It reports the loss in watts, the heat per metre, the share of the load and the yearly energy.

How is the cable loss calculated?

The loop resistance is the sum of each section's nominal ohms per km at 20 degrees C, corrected for temperature, times its length. The same current flows through the whole series loop, so the loss is the current squared times the resistance, and each section's loss adds directly. Halving the current cuts the loss to a quarter, so the lower steps lose much less than full brightness.

Can I enter the length one-way or in feet?

Yes. You can enter the total loop length (out and back) or the one-way route length, which is doubled for the loop. The length unit can be metres or feet. Each section can use a listed conductor or a custom conductor in ohms per km at 20 degrees C taken from your cable data sheet.

How do the brightness steps and operating hours work?

Choose a step preset (5-step 6.6 A, 3-step 6.6 A, 5-step 20 A, or a custom table) and enter the share of operating hours on each step. The 4,000 hours and the shares shown are placeholders, so replace them with your own airfield operating profile and check step currents against your CCR data sheet.

How are the yearly energy and cost worked out?

Energy is the sum over the steps of the loss times the hours on that step, divided by 1,000, where the hours are the operating hours times the step's share. Cost is the energy times the price per kWh, in any currency. Leave the price at 0 to skip the cost.

What are the share of load and the heat per metre?

The share of load is the full-brightness loss divided by the real load in watts, times 100. Enter the real power of the lamps and transformers, not including the cable loss, and leave it at 0 to skip. The heat per metre is the full-brightness loss divided by the loop length.

Can you give a worked example?

A #8 AWG loop of 3,000 m at 20 degrees C has a resistance of 6.306 ohms. The loss is 274.7 W at 6.6 A, 170.5 W at 5.2 A and 49.4 W at 2.8 A. At 6.6 A the heat is 0.092 W per metre, the share of a 5 kW load is 5.49 percent, and the energy over 4,000 hours at the default shares is 440.5 kWh.

What does the tool not do?

It does not calculate voltage drop (see Calculator #15), or include isolating transformer or fixture losses, connectors, splices, reactance or aluminium conductors. Resistance is held constant across steps and the cable's own heating is ignored. Resistance values are nominal DC figures, so final design shall be verified against the cable manufacturer's data and the project specification.

Important Notice, Disclaimer & Limitation of Liability

Please read before relying on any content on this page or on any result or record produced by it.

Specific to this page: Applies to the Cable Power Loss (calculator), including its PDF reports.

Calculated results. Results, tables, charts, status indicators (such as “OK”, “within limit” or “pass”/“fail”), recommended or selected values and the example presets on this page are first-pass planning and training estimates calculated in your browser from the values you enter, using simplified formulas, generic tables and typical values. They do not take account of every factor of a real installation, may contain errors or rounding differences, and are not a design, specification, selection, sizing, procurement or acceptance decision. A competent person must check them against the approved design, the manufacturer’s data and the applicable standard before any use. “Recommended” means an indicative estimate, not an endorsement of any rating, product or supplier.

Electrical values. Voltage, current, resistance, impedance, power, power factor, voltage drop, loss, load, capacity and efficiency figures depend on cable data, temperature, connector and transformer losses, CCR type, tolerances and other site conditions that a simplified calculation cannot fully capture. Default and example values are typical only. Do not rely on a result to load, energise, re-rate, tap or modify any circuit, CCR, cable or transformer.

Reports, downloads and printouts. PDF reports, CSV files and printed pages produced by this tool are uncontrolled working records generated in your browser. They are not approved designs, drawings, controlled documents, certificates, permits or regulatory records. Calculator numbers, revision labels, dates, project names, signature or approval fields on them are layout only and carry no authority unless made under your own approved document-control system. You must not present an output as an approved, verified or certified document. If you enter personal or confidential information, you are responsible for handling any exported file lawfully, including under the Digital Personal Data Protection Act, 2023.

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Educational reference only. This page is general information for competent, suitably trained and authorised aviation and electrical personnel and for learners. It is not professional engineering, legal, regulatory or safety advice, is not an approved procedure, and creates no professional or client relationship. Values, tolerances, intervals, sequences and examples are generic and indicative; real installations differ by design, make, model, age and condition, and your aerodrome’s approved procedures and the manufacturer’s documents prevail.

Standards and regulations. References to ICAO, FAA, IEC, IEEE, ISO, BIS (IS), DGCA, AAI and other documents are paraphrased summaries for orientation. They are not official text, may be incomplete or superseded, and do not state what any airport, project or regulator requires. Always consult the current official editions and the controlling project specification. Using this tool, or following its output, does not guarantee compliance with any law, standard or approval, and nothing on this page states that any airport, product or project complies or does not comply.

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Notice v2.9 · 27 October 2026 · Full terms: Legal & Disclaimer

Cable Power Loss

Cable Sections

Brightness Steps & Operating Time

Report details

Loss by Brightness Step

Build-up

Conductor Comparison

How the loss is calculated

1. Loop resistance

2. Loss at each step

3. Yearly energy and cost

4. Share of load and heat per metre

Worked example

What this tool does not do

Cable Power Loss Calculator: Frequently Asked Questions

Related Knowledge Hub Resources

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Calculator #15

Calculator #13

AGL Toolkit

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Important Notice, Disclaimer & Limitation of Liability