UPS and battery backup calculator: how it works
Tick the fans, lights and other appliances that must keep running when the electricity goes, choose how many hours of backup you need, and see the inverter size and battery bank. Heavy appliances like ACs and irons are left off backup by default because they make the battery bank very expensive.
How many batteries do I need for 4 hours of backup?
It depends on what runs during load-shedding. Three fans, six LED lights, a router and a fridge (about 475 W) need roughly two 200 Ah tubular batteries for 4 hours. Enter your own appliances above for your exact figure.
Can one battery run a fan all night?
A normal ceiling fan uses about 80 W. One 200 Ah tubular battery can run two or three fans for around 4–5 hours while staying within a healthy discharge level. DC inverter fans use less than half the power.
How the solar and UPS sizes are worked out
- Inverter / UPS: the total power of everything on backup, plus room for the largest motor (fridge, pump) starting up, with a 25% safety margin.
- Batteries: backup load × hours, allowing for inverter losses. Tubular batteries are sized to use only half their capacity (longer life); lithium uses 80%.
- Solar panels: your daily electricity use divided by the useful sun hours where you live (about 4.5–5.5 hours in Pakistan), allowing 25% for heat, dust and wiring losses.
These are planning estimates to help you talk to installers and compare quotes. A qualified installer should check your wiring, roof and exact equipment before you buy.
Questions
Can a UPS run my AC?
An inverter AC needs a large inverter and battery bank to run on backup. It is usually more practical to run the AC on solar during the day, and keep fans, lights and the fridge on battery backup at night.
Tubular or lithium battery?
Tubular batteries cost less but are heavy, need water top-ups and last about 3–5 years. Lithium (LiFePO4) costs more but lasts much longer, needs no maintenance and can use more of its capacity.
How many units will solar save on my bill?
The "units per month" figure is your appliances' estimated use. A solar system of the size shown is designed to produce about that much on an average day. Actual savings depend on sun, season and whether you have net metering.