Cable Power Loss Calculator
Power wasted as heat in a cable run, and what that waste costs over a year.
Results
Power lost in the cable
131.25
W
Resistance
0.14583
Ω
Energy
287.44
kWh/a
Cost
51.74
What this tool does
Losses rise with the square of the current, so doubling the load quadruples the heat in the cable. Putting a price on that waste is often what justifies the next cable size up: a thicker conductor costs once, the losses cost every hour the circuit runs.
Formula
P = I² × R , R = 2 × ρ × L ÷ S
Variables
| Symbol | Meaning | Unit |
|---|---|---|
i | Current | A |
l | One-way cable length | m |
s | Conductor cross-section | mm² |
ro | Resistivity | Ω·mm²/m |
h | Hours per day | h |
pr | Price per kWh | — |
PL | Power lost in the cable | W |
R | Resistance | Ω |
EY | Energy | kWh/a |
CY | Cost | — |
Worked example
- Current30 A
- One-way cable length25 m
- Conductor cross-section6 mm²
- Resistivity0.0175 Ω·mm²/m
- Hours per day6 h
- Price per kWh0.18
- Power lost in the cable131.25 W
- Resistance0.14583 Ω
- Energy287.44 kWh/a
- Cost51.74
Limitations
- Electrical installations are governed by national wiring rules. Cable sizing also depends on installation method, grouping, ambient temperature and protection devices, which this calculator does not evaluate.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.