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House Electrical Load Calculator

List the appliances in your home with their watts, how many and how long they run, and tick the ones that run together, to see your connected load and peak demand in kW, the main MCB and wire size, the load to apply for and your units a month.

Watts are starting values: use the figure on each appliance's rating plate. Tick 'At peak' for what runs together at your busiest time, like a summer evening. Fridges and ACs cycle, so count their hours at full power.

Supply
Voltage, power factor and spare capacity
V

230 V in most of India

1 for heaters; lower for motors, ACs and LED drivers

%

Room for growth on top of the peak

Main MCB
16 A, 2-pole (DP)
Peak demand
2.38 kW, 11.5 A
Connected load
8.83 kW
Main cable (copper)
2.5 sq mm or larger
Load to apply for
At least 3 kW
Units a month
713 kWh
Sub-circuits (IS 732)
2 lighting, 5 power
Everything on at once
42.7 A
Biggest users of units
AppliancekWh a monthShare
AC 1.5 ton36050%
Ceiling fan9013%
Refrigerator608%
Geyser (storage)608%
Water pump (1 hp)304%
  • Peak 2,384 W at 230 V and power factor 0.9 draws 11.5 A; with 25% spare that's 14.4 A, so the next standard MCB is 16 A.
  • With everything on at once the house would draw 42.7 A and trip a 16 A MCB: stagger the geyser, iron, microwave and pump, or tick them as at peak for a bigger MCB.
  • Wire must carry at least the MCB's current. Makers' charts for copper PVC wire in conduit give about 1.5 sq mm 14–16 A, 2.5 sq mm 19–22 A, 4 sq mm 26–29 A, 6 sq mm 34 A; check the datasheet of the wire you buy, as heat and bunching lower it.
  • Use B-curve MCBs for lights and sockets and C-curve for the AC and pump circuits, which draw a surge as they start.
  • IS 732 puts at most 10 points and 800 W on a lighting sub-circuit and about 3,000 W on a power sub-circuit.
  • DISCOMs sanction load in kW; some go by the connected load (8.83 kW here) or by the maximum demand on your meter, so check your DISCOM's rule before you apply.

An estimate to plan with: a licensed electrician must design and test the wiring. Everything runs in your browser.

How to use the house electrical load calculator

  1. Start from the two-bedroom list or clear it, and add your appliances from the list or as "Other".
  2. Change each appliance's watts to the figure on its rating plate, and enter how many you have and the hours a day it runs.
  3. Tick "At peak" for everything that runs together at your busiest time, such as a summer evening with the AC on.
  4. Choose single-phase or three-phase, and read the peak demand, main MCB, wire size, load to apply for and units a month.

Worked example

The starting two-bedroom list has a connected load of 8,834 W. On a summer evening the lights, fans, TV, fridge, computer and a 1.5-ton AC run together: 2,384 W, which at 230 V and a power factor of 0.9 is 11.5 A. With 25% spare that's 14.4 A, so a 16 A main MCB with 2.5 sq mm copper wire or larger, and a sanctioned load of at least 3 kW. A second 1.5-ton AC at peak makes it 3,884 W and 18.8 A; with the spare, 23.5 A needs a 25 A MCB and 4 sq mm wire. Everything on at once would draw 42.7 A, so the geyser, iron, microwave and pump are best run at other times.

The method

  • Connected load = Σ watts × number; peak demand = the same for what runs together
  • Current = watts ÷ (voltage × power factor); on three-phase, appliances are shared over the phases and the busiest phase counts
  • Main MCB = the next standard size (6, 10, 16, 20, 25, 32, 40, 50, 63 A) at or above the peak current plus spare
  • Wire: the smallest size whose rating (lower makers' figure) is at least the MCB's
  • Sub-circuits (IS 732): lighting at most 10 points and 800 W; power about 3,000 W and two outlets
  • Units a month = Σ watts × number × hours a day × 30 ÷ 1,000

An estimate to plan with, not a wiring design: a licensed electrician must size, install and test the wiring to IS 732 and your DISCOM's rules. Everything runs in your browser.

Frequently asked questions

How do I calculate the electrical load of my house?

Multiply each appliance's watts by how many you have and add them up: that's the connected load. A two-bedroom flat with six LED bulbs, four tube lights, four fans, a TV, fridge, computer, a 1.5-ton AC, washing machine, mixer, iron, microwave, geyser and a water pump, at the starting wattages here, comes to 8,834 W, or 8.83 kW. Not everything runs at once, so the peak demand of what does is what sizes the main MCB.

What is the difference between connected load and sanctioned load?

Connected load is the total rating of everything you could switch on. Sanctioned load is what your DISCOM (electricity distribution company) has approved for your connection, in kW. Peak demand is what actually runs together; in the example it's 2,384 W, so at least 3 kW. Some DISCOMs assess the connected load or go by the maximum demand your meter records, so check your DISCOM's rule.

Which MCB should I use for my house?

Work out the current at peak: watts ÷ (230 V × power factor). The example's 2,384 W at a power factor of 0.9 draws 11.5 A; with 25% spare that's 14.4 A, so a 16 A main MCB, double-pole on a single-phase supply. Use B-curve MCBs for lights and sockets and C-curve for ACs and pumps, which draw a surge when they start.

What wire size do I need for house wiring?

The wire must carry at least the current of the MCB that protects it. Makers' charts for copper PVC house wire in conduit give about 14–16 A for 1.5 sq mm, 19–22 A for 2.5 sq mm, 26–29 A for 4 sq mm and about 34 A for 6 sq mm, so by the lower figures a 10 A MCB suits 1.5 sq mm, 16 A suits 2.5 sq mm, 25 A suits 4 sq mm and 32 A suits 6 sq mm. Heat and bunching lower these ratings: check the datasheet of the wire you buy, and let a licensed electrician decide.

How many points can go on one circuit?

IS 732, the Indian code for wiring installations, puts at most 10 points (lights, fans and small sockets) and 800 W on a lighting sub-circuit, and normally at most 3,000 W and two outlets on a power sub-circuit. The example's 14 light points need 2 lighting circuits and its 10 power appliances at least 5 power circuits.

How many units of electricity will my house use?

Each appliance uses watts × hours a day ÷ 1,000 units (kWh) a day; times 30 for a month. Fridges and ACs switch on and off, so count their hours at full power. The example uses about 713 units a month, more than half of them for the AC running 8 hours a day.

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