Cable loss running cost
Ano ang natitipid sa energy, gastos at CO2 kapag nag-size up ng cable.
Reads AS/NZS 3008.1.2:2017 (NZ) and AS/NZS 3008.1.1:2017 (AU). Tables checked 24 Sept 2026.
Subukan ang isang job 4
Nilalagyan ng halimbawang value ang bawat job. Palitan ang mga ito ng sarili mong value.
- What a size up saves on a feederThe yearly saving of 120 over 95 mm² on a 200 A feeder that never stops.
- Running cost of a heat pump circuitThe energy a 6 mm² heat pump circuit loses a year, against 10 mm².
- Payback of a larger submainHow fast 35 mm² pays back over 25 mm² on a busy 80 m submain.
- CO2 saved by a larger aluminium cableThe kWh and CO2 a year of 120 over 95 mm² aluminium at 150 A.
Mga input
Worked example gamit ang mga default na input.
- Hurisdiksyon
- NZ · AS/NZS 3008.1.2
- Mga phase
- Three phase
- Running current, rms
- 100 A
- Oras ng takbo kada taon
- 4,000 h
- Haba ng ruta
- 60 m
- Conductor
- Tanso
- Insulation
- XLPE 90 °C
- Sukat na pumapasa
- 35 mm²
- Sukat na ikukumpara
- 50 mm²
- Energy tariff
- 0.3 $/kWh
- Emission factor
- 0.1 kg/kWh
- Dagdag na gastos ng mas malaking laki
- 800 $
Natipid na gastos kada taon
$375.84
- Natipid na enerhiya kada taon
- 1,252.8kWh
- CO2 na natipid kada taon
- 125.3kg
- Pagbabalik ng dagdag na gastos
- 2.1years
- Enerhiyang nawawala kada taon, 35 mm²
- 4,809.6kWh
- Enerhiyang nawawala kada taon, 50 mm²
- 3,556.8kWh
Design aid lang ang resultang ito. I-verify ito laban sa kasalukuyang standard.
Mga hakbang ng kalkulasyon
- 35 mm² a.c. resistance sa 90 °C0.67Ω/km
AS/NZS 3008.1.2:2017 Table 30 (Xc), Tables 34–35 (Rc) p.98, p.102–103
- 35 mm² loss: 3 × 100² × R × 60 m1,202.4W
- 35 mm² na enerhiyang nawawala kada taon, sa loob ng 4000 h4,809.6kWh
- 35 mm² ang gastos kada taon, sa $0.30 bawat kWh$1,442.88
- 50 mm² a.c. resistance sa 90 °C0.49Ω/km
AS/NZS 3008.1.2:2017 Table 30 (Xc), Tables 34–35 (Rc) p.98, p.102–103
- 50 mm² loss: 3 × 100² × R × 60 m889.2W
- 50 mm² na enerhiyang nawawala kada taon, sa loob ng 4000 h3,556.8kWh
- 50 mm² ang gastos kada taon, sa $0.30 bawat kWh$1,067.04
- Natipid na enerhiya kada taon1,252.8kWh
- Natipid na gastos kada taonResulta$375.84
- CO2 na natipid kada taon125.3 kg
- Pagbabalik ng dagdag na gastos2.1 taon
Tungkol sa calculator na ito
How this is calculated
Every cable turns some of the energy it carries into heat. The loss is the current squared times the resistance of the conductors that carry it. A larger cable has less resistance, so it wastes less. This tool puts a yearly figure on that waste for two sizes, so you can see what the size up saves.
The tool reads the a.c. resistance of each size from AS/NZS 3008.1, in ohms per kilometre, for the conductor metal and insulation you pick. It reads the table at the conductor's full-load temperature. On a single‑phase circuit the current flows out and back, so two conductors carry the loss. On a balanced three‑phase circuit the neutral carries no current, so three do.
The loss in watts is the number of loaded conductors times the current squared times the resistance times the length. The tool multiplies it by the running hours a year to get kWh. The tariff turns kWh into dollars, and the emission factor turns kWh into kilograms of CO2. Both are figures you set from your own contract and grid.
The difference between the two sizes is the saving a year. If you enter what the size up costs over the smaller cable, installed, the tool divides that by the saving to give the payback in years.
Enter the rms current over the running hours, not the mean or the peak. Loss grows with the square of the current, so a cable that runs near full load for long hours gains the most from a size up.
| Step | Table or clause | What it decides |
|---|---|---|
| Resistance of each size | Tables 34 and 35 | The ohms per kilometre at the full-load temperature |
| Loss | n × I² × R × L | The watts each size wastes |
| Energy a year | Loss × running hours | The kWh each size wastes |
| Cost and CO2 | Tariff and emission factor | Dollars and kilograms a year, from your figures |
| Payback | Extra cost ÷ saving a year | The years for the size up to pay for itself |
Worked examples
- A 100 A feeder of 60 m in 35 or 50 mm² XLPE saves $375.84 a year with the size up. That is 1,252.8 kWh a year, and the extra $800 pays back in 2.1 years.
- A 200 A feeder of 120 m that never stops, 95 or 120 mm² saves $1,892.16 a year. That is 6,307.2 kWh a year, and the extra cost pays back in 1.3 years.
- A 25 A heat pump circuit of 40 m in 6 or 10 mm² PVC saves $68.40 a year. That is 228 kWh a year, and the extra cost pays back in 2.2 years.
- A 150 A aluminium feeder of 100 m, 95 or 120 mm² saves $870.75 a year. That is 2,902.5 kWh a year, and the extra cost pays back in 1.7 years.
Limits
The resistance is the table figure at the full-load temperature. A cable at part load runs cooler, so the real loss is a little lower than the tool shows.
The tool does not size the cable. Size it first for current, voltage drop and fault with the cable size tool, then compare the size that passes with the next size up. It does not count the time value of money, a tariff that changes through the day, or harmonic currents, which add loss.
See also: Cable size, Voltage drop and Three phase power.
Mga tanong
Design aid ang resulta. I-verify ito laban sa kasalukuyang standard.
Paano kinakalkula ang enerhiyang nawawala sa cable?
I-multiply ang bilang ng loaded conductor sa current squared, sa resistance kada metro, at sa haba. Iyon ang loss sa watts. I-multiply ang loss sa running hours, hinati sa 1000, para makuha ang kWh kada taon. Binabasa ng tool ang resistance mula sa AS/NZS 3008.1.
Nakakatipid ba ang mas malaking cable?
Mas mababa ang resistance ng mas malaking cable, kaya mas kaunti ang nawawalang enerhiya. Sa mahabang run na may mataas na current sa maraming oras, puwedeng mabawi ng tipid ang dagdag na cable sa loob ng ilang taon. Sa maikli o bihirang gamiting run, bihira itong mangyari.
Bakit upper bound ang loss?
Binabasa ng tool ang resistance sa full-load temperature ng cable, 75 °C para sa PVC at 90 °C para sa XLPE. Ang cable sa part load ay mas malamig ang takbo at mas mababa ang resistance nito, kaya bahagyang mas mababa ang tunay na loss. Ganoon din ang savings, at ang payback ay lower bound.
Anong tariff at emission factor ang dapat kong gamitin?
Gamitin ang energy rate sa kontrata ng supply mo, kasama ang anumang time-of-use split na tumutugma sa mga oras. Para sa CO2, gamitin ang inilathalang emission factor ng grid mo. Pareho itong assumption na ikaw ang nagtatakda. Walang hawak ang AmpSize sa alinman sa dalawa.
Pinapalitan ba nito ang cable size check?
Hindi. I-size muna ang cable para sa current, voltage drop at fault gamit ang cable size tool. Pagkatapos, ihambing ang size na pumasa sa susunod na mas malaking size dito.
Mga clause at table na binabasa ng tool na ito
- AS/NZS 3008.1.2:2017 Table 30, 34, 35Reactance at 50 Hz and a.c. resistance at 50 Hz
- AS/NZS 3008.1.1:2017 Table 30, 34, 35Reactance at 50 Hz and a.c. resistance at 50 Hz
Bawat clause at table, kasama kung paano ito na-verify
Huling na-check ang mga table noong 24 Sept 2026.
Mga kaugnay na tool
- Cable size calculatorFind the smallest cable size that passes each check.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Voltage drop calculatorCalculate voltage drop on a cable run and check the limit.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Cable fault rating calculatorCheck that a conductor can withstand the fault current.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
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