House & Building Electrical Point Estimator

What this estimates, and what it does not

Most load calculators start from equipment: list every appliance, add up the watts, size the supply. That works once a building is occupied and you know what is in it. It is useless at the point where the wiring is actually decided — a floor plan, room names, and no idea yet which fridge the client will buy.

This works the way a wiring quotation works. Each room type carries a conventional set of points, the areas scale the ones that scale, and the totals give you the point count for the estimate, the circuit count for the board, and a connected load figure to check the sanctioned supply against.

The point rules

These are conventional Indian practice, not code. IS 732 governs how circuits are protected, separated and earthed. It does not say how many sockets a bedroom gets — that is habit, client expectation and local norm, and it varies between cities, between contractors, and between a builder flat and an owner-built house.

Where practice quotes a range, the calculator picks from area:

• Bedroom — one fan, two lights, three 5A sockets and a 15A AC point up to 120 sqft. Above that it is treated as a master bedroom: second fan, third light, fourth socket, and a second 15A point past 180 sqft.
• Living / hall — a fan per 100 sqft and a light point per 80 sqft, both rounded up, with four to six 5A sockets by size.
• Kitchen — no ceiling fan, two lights, an exhaust fan, and two 15A points for the chimney and the refrigerator.
• Bathroom — a 15A geyser point, an exhaust fan, and a second light point once over 40 sqft.
• Utility — a 15A point for the washing machine.

Fractions always round up. A 100 sqft hall gets one fan; a 250 sqft hall gets three, not two and a half.

The wattage assumptions

A socket has no load of its own — it has whatever gets plugged into it. The connected load figure uses these planning allowances:

Every one of these is editable — open “Load assumptions” under the room list. They are planning conventions rather than measurements, and the right figure depends on what actually goes into the building.

The fan is the one worth changing first, because it is the one that has genuinely moved. The 75 W default is a conventional induction-motor fan. A BLDC fan doing the same job draws about 35 W, and there is a preset for it: on a house with a dozen fans that is roughly half a kilowatt off the connected load.

The 15A figure dominates the total, so it is the next to look at. A 1.5 ton air conditioner is nearer 1600 W, a 25 litre geyser 2000 W, a washing machine 500 W except while it heats. Averaging them at 1500 W is a convention, not a measurement — if your 15A points are mostly geysers, put 2000 W in and the estimate will reflect it.

Light points assume LED. A house on 40 W tubes or 60 W filament lamps needs that figure raised by three or four times, though it remains a small share of the total either way.

Changing these moves the connected load and maximum demand figures only. Point counts and circuit counts come from the room rules and are unaffected.

Connected load against maximum demand

Connected load is everything switched on at once, which never happens. Nobody runs the geyser, both air conditioners, the washing machine and every light simultaneously. The supply is sized on maximum demand — connected load times a diversity factor.

This tool applies 40 % for residential, 60 % for commercial and 75 % for industrial. Those are broad planning figures; a sanctioned load application is worked out from the utility's own schedule. There is more on where diversity comes from in connected load, maximum demand and diversity.

How the circuits are split

Points are grouped into final circuits so that no circuit carries more than it should, and so a fault takes out one part of the house rather than all of it:

• Lighting circuits — 8 points each, covering fans, light points and exhaust fans. The 5A sockets ride here too, which is normal Indian practice; a specification that wants them separated will need more circuits than this shows.
• Power circuits — 2 of the 15A points each. These are 2 kW-class loads, and a geyser or an air conditioner is normally given a circuit of its own regardless of the count.

The board is then sized from the circuit total: 8-way DB, 12-way DB, 18-way DB, and beyond that a distribution panel with more than one board. Those way counts are outgoing MCB positions — the incomer and the RCD sit outside them, which is one reason sizing exactly to the circuit count leaves you with no spare way for the circuit somebody adds later.

What this estimate is not

It is a starting point for a quotation and a board schedule, not a design. It does not place the points, decide switch positions, size the cable, choose the protective devices, or account for anything unusual in the building. Cable size depends on the run length and the installation conditions — see the cable sizing calculator — and protection has to match both the cable and the load, which is the breaker sizing calculator.

Estimates are based on standard wiring practice and should be verified by a licensed electrician before implementation.