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Free Inverter & Battery Calculator

Inverter VA, battery Ah and backup hours for what you need to run in a power cut.

VA + Ah Backup hours Nothing uploaded
See the letter and download ↓

Estimate for

What runs during a power cut

ApplianceWattsHow many

Watts are on the label or in the manual of each appliance. Use the real numbers of your home or shop.

Backup and battery

From the battery you were quoted.

Settings (rules of thumb — change to the figures of your inverter and battery)

Depth of discharge from the battery maker. Lead-acid makers often advise less than lithium.

Prices (optional)

Fill in the prices you were quoted to get a cost estimate. Leave empty for quantities only.

Everything you type stays in your browser — nothing is uploaded or saved.

Settings come from your manuals.

Two numbers

Inverter size (VA) depends on what runs at the same time; battery size (Ah) depends on that load and how many hours you need. Power factor, efficiency and usable battery % are rules of thumb — use the figures in your inverter and battery manuals.

Kaise use karein

  1. Bijli jaane par jo chalega uske watt aur sankhya bharein.
  2. Kitne ghante backup chahiye, bharein.
  3. Inverter VA aur battery dekhein; PDF download karein.

Dhyan dein

Settings apne inverter aur battery ke manual se badlein.

Questions people ask

What size inverter do I need?
Add the watts of everything that runs at the same time and divide by the power factor (0.8 is a common rule of thumb; your inverter’s manual gives its own). Choose the next VA size up.
How do I calculate battery backup?
Backup hours = battery voltage × Ah × usable % × inverter efficiency ÷ load in watts. The page works it out for the batteries you choose.
Why not use the full battery?
Batteries last longer when they are not fully emptied. The usable % (depth of discharge) comes from the battery maker; lead-acid makers often advise less than lithium.
Is my data uploaded?
No. Everything is worked out in your browser.

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Questions & problems

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