What is it?
The Inverter and Battery Calculator tells you what size of home inverter and battery you need for a power cut. From the appliances you want to run and for how long, it shows the inverter size (VA), the battery capacity (Ah) and the batteries to buy.
Who is it for?
Families in areas with power cuts, shops and small offices, and electricians sizing inverters.
How to use it
- Add up the Total load to run (fans, lights, TV, router) in watts: for example 3 fans × 75 + 6 LED bulbs × 10 + TV 100 + router 10 = 395 W.
- Enter the Backup needed in hours, the Battery voltage (12 V one battery, 24 V two, 48 V) and the Battery type: Lead-acid / tubular (use 50%) or Lithium (use 90%).
How it is worked out
It allows 85% inverter efficiency and the safe depth of discharge for the battery type. Lead-acid batteries last longer if you use only about half their capacity.
Common mistakes
- Counting the wattage printed on fans at full speed is fine; ceiling fans on slower speeds use less.
- Fridges, pumps and ACs need extra capacity for start-up: their motors draw 3–5 times their running power for a moment. Most home inverters can’t run ACs.
- Battery Ah ratings assume slow discharge; heavy loads give less backup than the label suggests.
Top up distilled water in tubular batteries every 2–3 months, and keep them in a ventilated place.
Errors and how to fix them
- “Enter the load (more than 0)”: add up the watts of everything you want to run in a power cut (fans, lights, TV) and type the total in Total load to run.
- The battery size looks huge: check Backup needed. Running a load for 8 hours needs twice the battery of 4 hours.
Open the tool: Inverter and Battery Calculator
Still stuck?
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Questions, or an error not listed here?
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