Sizing the mains and circuits starts with knowing your total connected load. Here is the simple method.
Step 1 — Add up appliance wattages
| Appliance | Typical power |
|---|---|
| LED lights & fans | 10–75 W each |
| Refrigerator | 150–350 W |
| Television | 50–150 W |
| Microwave | 1000–1500 W |
| 1.5-ton air conditioner | 1500–1800 W |
| Geyser / water heater | 2000–3000 W |
| EV home charger | 3300–7400 W |
Step 2 — Apply a diversity factor
You never run everything at once, so multiply the grand total by a diversity factor of about 0.6–0.8 to get a realistic maximum demand.
Step 3 — Convert to current
For a single-phase 230 V supply, current (A) = power (W) ÷ 230. For example, a maximum demand of 6 kW ≈ 26 A, which points to a 6 sq mm copper main and an appropriately rated main switch.
Step 4 — Size each circuit
Give heavy appliances (AC, geyser, EV charger) their own dedicated circuit and wire size, and keep lighting and general sockets on separate circuits. Use our appliance wire-size chart and MCB-to-wire chart to finish the job.
Indicative guidance for typical Indian domestic installations. Always confirm final cable sizes against the applicable IS standards, your local wiring rules and a licensed electrician for your specific installation.