Quick answer
Ampacity — short for 'ampere capacity', also called current-carrying capacity — is the maximum electric current a cable can carry continuously without its temperature rising beyond a safe limit. Exceed it and the conductor overheats, which degrades the insulation and creates a fire risk.
A cable's ampacity is not a single fixed number; it depends on several factors:
- the conductor size (larger cross-section carries more current);
- the insulation's temperature rating — higher-rated insulation such as XLPE allows more current than standard PVC;
- how the cable is installed (in conduit, buried, in free air);
- the ambient temperature; and
- grouping with other cables, which traps heat.
This is why cable sizing follows standard tables and a proper calculation rather than guesswork, and why long runs may need a size up to also control voltage drop. See how to choose the right cable, and APAR's house wires and cables for the available sizes.