Electricity & Power Backup Calculators: Solar, Inverter, Generator and Power Bills
Power cuts and rising bills are both sums in watts and hours. These 9 calculators size solar panels, inverter batteries and generators for the load you need to run, work out what each appliance costs per month in units, show LED savings, convert lumens to watts, and pick the right wire size, battery charge time and power bank capacity.
- 9 free tools
- No sign-up
- Made for India (₹, Indian sizes)
- Updated
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Frequently asked questions
What size inverter battery do I need?
Add the watts of everything that must run in a power cut, multiply by the backup hours, and divide by the battery voltage and efficiency. Running 300 W for 3 hours needs about a 150Ah 12V battery once you allow for losses and not draining it fully.
How many solar panels do I need?
Divide your daily units (kWh) by the peak sun hours (about 4–5 in most of India) to get the kW size, then by each panel's rating. 4 units a day needs about a 1 kW system.
How do I work out an appliance's power cost?
Watts × hours used per day × 30 ÷ 1,000 gives units per month; multiply by your tariff per unit.
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