Load shedding makes batteries the most important part of many solar systems in Pakistan. This solar battery backup calculator tells you how many kWh, how many amp-hours and how many batteries you need to run your load for the hours you choose.
Solar Battery Backup Calculator
Load shedding mein kitni battery chahiye? Load aur backup ghante daalein.
Lithium: 90% usable depth of discharge. Tubular: 50% to protect battery life. Includes inverter losses.
How to use the battery calculator
- Backup load: add up the watts of what you want running during an outage. Fans and lights for a typical home are 300–800 W; one inverter AC adds about 1,000–1,500 W.
- Backup hours: the longest outage you want to cover, or the night hours you want to run on battery.
- Battery type and voltage: most new hybrid inverters use 48V batteries.
How the calculation works
- Usable energy = load (W) × hours.
- Battery size = usable energy ÷ (depth of discharge × inverter efficiency).
- Lithium batteries can safely use about 90% of their capacity. Tubular lead-acid batteries should only be drained to about 50% to last longer.
Running 800 W for 4 hours needs 3.2 kWh of usable energy. With lithium that’s about 3.7 kWh of battery (one 5.12 kWh module). With tubular batteries it’s about 7.5 kWh, or four 12V 200Ah batteries at 48V.
Lithium vs tubular batteries
| Lithium (LiFePO4) | Tubular lead-acid | |
|---|---|---|
| Usable capacity | About 90% | About 50% |
| Life | Typically 3,000–6,000 cycles | Typically 3–5 years |
| Maintenance | None | Water top-up needed |
| Upfront cost | Higher | Lower |
| Best for | Daily cycling, long backup | Short, occasional backup on a budget |
Because lithium lets you use almost twice as much of its capacity and lasts many more cycles, it is often cheaper per unit stored over the battery’s life, even though it costs more upfront.
Don’t forget the solar panels
Batteries need charging. To refill a 5 kWh battery each day while also running your home, you need roughly 1.2–1.5 kW of extra panels on top of your daytime needs. Size the panels with our solar load calculator and choose a battery-ready inverter using the 5kW inverter guide.
Frequently asked questions
How many batteries do I need for a 5kW solar system?
It depends on your backup load, not the panel size. Running 1 kW for 5 hours needs about 5.8 kWh of lithium (two 5.12 kWh modules) or about 12 kWh of tubular batteries.
How long will a 5 kWh lithium battery last during load shedding?
About 4.3 usable kWh after losses. That runs an 800 W load for around 5 hours, or a 1.5 kW load (one inverter AC plus fans) for under 3 hours.
Can I run an AC on solar batteries at night?
Yes, but it needs a large battery. One 1.5-ton inverter AC running all night can use 6–9 kWh, which means two to three lithium modules.
Prices and rules change often. This page was last reviewed on 12 November 2026. Spotted an outdated rate? Tell us and we'll update it.