AC Electrical Line Sizing Guide
Undersized AC wiring is one of the most common causes of house fires in Egypt. Too-small cable overheats and burns — oversized cable wastes money. This guide gives you exact figures for every AC size.
By the Ases Kahraba team — Last updated: February 2026
Quick Answer
Complete guide to sizing your AC electrical line — amperage calculations, cable cross-sections, and circuit breaker sizing for 1 to 4 HP air conditioners.
AC Electrical Wiring Essentials
- Amperage calculation rule: 1 kW ≈ 4.5 A at 220 V. 1 HP AC ≈ 0.75 kW = ~7 A. 1.5 HP ≈ 1.1 kW = ~10 A. 2 HP ≈ 1.5 kW = ~14 A.
- Recommended cable sizes: 1–1.5 HP → 2.5 mm² (3-core × 2.5). 2–2.5 HP → 4 mm². 3–4 HP → 6 mm². These are panel-to-outdoor-unit cable sizes.
- Circuit breaker sizing: use 125% of operating current. 1.5 HP (10 A) → 16 A breaker. 2 HP (14 A) → 20 A breaker. 3 HP (20 A) → 25 A breaker.
- Dedicated circuit per AC: never share an AC circuit with any other load — run a dedicated line from the main panel to each outdoor unit.
- Inverter AC units: inverters draw higher inrush current at startup. Size the breaker at 150% of running current to avoid nuisance tripping.
- Three-phase AC units: large units (2.5+ HP in villas) may be three-phase — requiring 5-core × 4 mm² cable and a 3-phase breaker.
- Cable run length: for every 10 m of extra cable length, increase the cross-section one step (2.5→4, 4→6) to compensate for voltage drop.
Quick Reference: AC × Cable × Breaker
| AC Capacity | Running Current | Cable Size | Breaker Size |
|---|---|---|---|
| 1 HP | ~7 A | 2.5 mm² | 10 A |
| 1.5 HP | ~10 A | 2.5 mm² | 16 A |
| 2 HP | ~14 A | 4 mm² | 20 A |
| 2.5 HP | ~18 A | 4 mm² | 25 A |
| 3 HP | ~20 A | 6 mm² | 25 A |
| 4 HP | ~28 A | 6 mm² | 32 A |
* Values for cable runs ≤ 20 m at 35°C ambient. Increase size for longer runs.
Frequently Asked Questions
Is 2.5 mm² cable enough for a 2 HP AC?
No — a 2 HP AC draws about 14 A, and 2.5 mm² cable is rated for a maximum of 20 A only in ideal conditions. Given Egypt's high ambient temperatures and longer runs, 4 mm² is required for safety and to avoid voltage drop.
Can two AC units share the same electrical line?
Absolutely not recommended — each AC needs its own dedicated circuit from the panel with its own breaker. Running two units on one line overloads the cable, causes overheating, and may start a fire.
What's the difference between the indoor and outdoor cable?
The main supply cable runs from the panel to the outdoor unit (compressor). A separate control/power cable links the outdoor to the indoor unit — this is usually specified by the AC manufacturer (3 or 4-core cable).
Does inverter AC actually save electricity?
Yes, 30–50% compared to a conventional On/Off unit of the same capacity. The inverter adjusts compressor speed to demand instead of constantly cycling on/off — significantly reducing long-term consumption.
What does it cost to wire an AC line in Cairo?
A single AC line (cable + breaker + connection) costs EGP 300–800 depending on run length and cable size. For complete systems including AC installation, contact us for a comprehensive price.