Inverter Size Calculator

A what size inverter do I need for my home Pakistan calculator that sizes your inverter from your appliance load. Use the free Inverter Size Calculator below — enter your values and get instant results, right in your browser. Total load (W) = Σ(quantity × rated watts); 1 HP = 746 W. Inverter (kVA) = total watts ÷ 0.8 (power factor) × 1.25 (safety margin) ÷ 1000. Example: 2,000 W ÷ 0.8 × 1.25 ÷ 1000 = 3.13 kVA → buy a 3.5 or 5 kVA unit.

How to use the Inverter Size Calculator

An undersized inverter trips the moment your fridge compressor kicks in; an oversized one wastes money. This what size inverter do I need for my home Pakistan calculator converts your appliance list into watts, then into the kVA rating inverters are actually sold in — accounting for power factor and a 25% safety margin. It works for both solar hybrid inverters and plain UPS inverters, since the sizing math is identical.

  1. Enter the quantity of each appliance you will run together at the same time — fans, bulbs, fridges, TVs, ACs, and water motors in HP.
  2. Count only appliances that run simultaneously; the iron you use for 10 minutes can usually be left out.
  3. Click Calculate to see your total load in watts and the required inverter size in kVA.
  4. Round UP to the next standard inverter size (1.5, 3, 5, 7.5, 10, or 15 kVA) when shopping.
  5. If the result sits just above a standard size, drop one heavy appliance to the grid instead of jumping a full size.

Formula

Total load (W) = Σ(quantity × rated watts); 1 HP = 746 W. Inverter (kVA) = total watts ÷ 0.8 (power factor) × 1.25 (safety margin) ÷ 1000. Example: 2,000 W ÷ 0.8 × 1.25 ÷ 1000 = 3.13 kVA → buy a 3.5 or 5 kVA unit.

Worked example

A home runs 4 fans (320W), 8 bulbs (96W), 1 fridge (150W), and 1 TV (100W) together — 666W total. Inverter = 666 ÷ 0.8 × 1.25 ÷ 1000 = 1.04 kVA, so a 1.5 kVA inverter is the right buy. Adding a 1 HP water motor (746W) pushes the load to 1,412W = 2.2 kVA, needing a 3 kVA unit.

Frequently asked questions

One fan (80W) plus four bulbs (48W) is 128W, which needs about 0.2 kVA — but the smallest practical home inverter is 1–1.5 kVA. Size up if you plan to add a fridge later.

A 1.5-ton inverter AC draws ~1,800W running, which alone needs about 2.8 kVA after power factor and margin — so a 3 kVA unit can handle the AC plus a few bulbs, but not the AC plus a fridge and motor together.

kW is real usable power; kVA is apparent power. Because home appliances have a power factor around 0.8, a 3 kVA inverter delivers roughly 2.4 kW. Always size in kVA using the 0.8 factor.

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