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Electrical Load Calculator

Home & Construction

Size a house connection — connected load, maximum demand, phase and main breaker.

Runs entirely in your browser — nothing is uploaded

The number to ask the utility for is not the connected load — the sum of every nameplate in the house — because no installation ever draws it. It is the maximum demand: what is realistically on at once. Ask for the connected load and you pay a fixed monthly charge on a connection two or three times larger than you need.

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Features

  • Appliance list with a preset wattage for each, and quantities.
  • Diversity factor by installation size, because nothing runs all at once.
  • Spare capacity, so a future air conditioner does not mean a new connection.
  • Single or three phase chosen automatically at the sanctioning threshold.
  • Current, kVA and the main breaker rating that follows.
  • Runs entirely in your browser — nothing is uploaded.

How to use the Electrical Load Calculator

  1. 1Add each appliance and how many of them there are.
  2. 2Choose the installation size, which sets the diversity factor.
  3. 3Set the spare capacity you want to leave.
  4. 4Read the sanctioned load to ask for, and the main breaker size.

Frequently asked questions

What is the difference between connected load and maximum demand?

Connected load is the sum of every appliance nameplate — everything you own, running at once. Maximum demand is what the installation actually draws at its busiest, which is far less, because you are not running the geyser, both air conditioners, the washing machine and the iron simultaneously. Utilities sanction on demand, and sizing on connected load buys a connection two or three times larger than needed.

What diversity factor should I use?

Roughly 80% for a small flat, 65% for a two or three bedroom flat, 55% for a house and 45% for a large one. The factor falls as an installation gets bigger because averaging works in your favour — the more appliances there are, the smaller the proportion running at any moment.

When do I need a three-phase connection?

Most Indian distribution companies sanction single phase up to somewhere between 5 and 10 kW and require three phase above it, and the exact threshold varies by state. Three phase also matters for large motors and for balancing: with three phase the load is shared across three lines, so the current in each is far lower and the cable can be smaller.

How do I convert kW to amps?

For single phase, amps = watts ÷ (230 × power factor). For three phase, amps = watts ÷ (1.732 × 415 × power factor). At a power factor of 0.9, a 5 kW load draws about 24 A single phase but only 7.7 A per line on three phase — which is why the same load needs very different cable and breakers depending on the supply.

What is power factor and why does it matter?

The ratio of real power in watts to apparent power in kVA. Motors, compressors and transformers draw current that does not all do useful work, so the supply has to carry more than the wattage suggests. Domestic installations sit around 0.85–0.95. Utilities bill larger consumers in kVA precisely because that is what their network has to carry.