Home Load Calculator

Connected load is not running load

Add every appliance in a house and a three-bedroom flat comes to eight or nine kilowatts. Nobody has ever drawn that. The geyser runs before work, the iron at the weekend, the oven on Sunday — and the air conditioning runs when the geyser does not. The ratio between what is installed and what runs together is the diversity factor, and for a home it sits between 0.5 and 0.8.

Sizing on connected load is not a safety margin, it is a bigger invoice. The default here is 0.70. Move it up if the house genuinely runs everything at once, down if the loads are staggered.

Inverters are sold in VA, appliances are labelled in W

Watts are the real work done. Volt-amperes are what the wiring and the inverter have to carry, and the two differ by the power factor. A refrigerator at 150 W and 0.65 power factor draws 231 VA — half again as much as its label suggests. Motors and old CFLs are the poor performers; heaters, kettles and induction hobs are close to unity.

This is why matching a 1000 VA inverter to 1000 W of appliances leaves you short. The calculator carries VA through every step and applies the power factor per appliance rather than averaging it.

The number that actually trips inverters

An induction motor pulls five to seven times its running current until it reaches speed. A 1 HP pump running at 850 W is asking for roughly 5.3 kVA for a second or two at every start. That transient never appears in a wattage total, and it is the single most common reason an inverter sized “to the load” shuts down when the tank fills.

The headroom bar takes the worst single start and lands it on top of everything already running — the correct case, because two compressors reaching locked rotor in the same half-cycle is a coincidence rather than a design condition. Most inverters hold about twice their continuous rating for a second, which is the peak line on the bar.

If the surge runs past that line, three things fix it: a larger inverter, a soft starter or capacitor-start kit on the offending motor, or an inverter-type air conditioner, which ramps its compressor instead of slamming it across the line.

What the battery figure means

Backup energy is running demand multiplied by hours, divided by inverter efficiency — about 90 % for a decent unit. Converting that to amp-hours needs the bank voltage and a usable depth of discharge: 80 % is reasonable for lithium, but a tubular lead-acid bank should be sized at 50 % if you want it to last. The battery bank calculator applies the C10 discharge-rate penalty properly, which matters once the discharge is faster than ten hours.

Where the appliance figures come from

The wattages are typical measured figures for equipment sold in India, not nameplate maxima — a nameplate states the worst case at the worst voltage, and sizing every appliance on it compounds a margin that is already in the diversity factor. Hours are actual running hours: the eight hours against a refrigerator is compressor time across a day, not the twenty-four it spends plugged in.

Anything that governs your answer deserves a look at its own rating plate. Air conditioners and pumps vary widely, and they are usually the two that decide the size.