Sizing your wiring, main switch and even your sanctioned supply all begin with knowing your total connected load — the sum of the wattage of every light and appliance in the home. But because you never switch everything on at the same moment, the figure your wiring actually has to handle is the maximum demand, which is smaller.
Step 1 — Add up the wattages
List every appliance with its rated power in watts (it is printed on the nameplate). Lights and fans are small (10–75 W each); the big loads are the microwave (~1.5 kW), air-conditioner (~1.5–1.8 kW for a 1.5-ton unit), geyser (2–3 kW) and an EV charger (3.3–7.4 kW). Add them all to get the connected load.
Step 2 — Apply a diversity factor
Multiply the total by a diversity factor of roughly 0.6–0.8 to reflect that only some loads run together. For example, a 9 kW connected load at 0.7 gives a realistic maximum demand of about 6.3 kW.
Step 3 — Convert watts to amps
On a single-phase 230 V supply, current (A) = watts ÷ 230. A 6.3 kW demand is therefore about 27 A, which points to a 6 sq mm copper main and a suitably rated main switch and MCB. On a three-phase supply the load is spread across the phases, so divide accordingly.
Give heavy appliances (AC, geyser, EV charger) their own dedicated circuits, keep lighting and general sockets separate, and have a licensed electrician confirm the final sizing for your layout. Our load-calculation guide works through a full example.