Lithium Battery Backup Time: How Many Hours Will It Run?
Lithium battery backup time depends on two numbers only: how much energy the battery stores (kWh) and how much power your home is pulling (watts). This guide gives the simple formula we use on every product page, ready-made tables for 12V, 24V, 5kW, 10kW and 16kW lithium batteries, and the real-world reasons your backup can come out shorter than the label suggests.
Updated 12 November 2026
The backup time formula
Every backup figure on our product pages uses one formula:
hours = kWh x 0.9 x 0.92 x 1000 / watts
- kWh is the battery's rated energy, for example 5.12 kWh for a 51.2V 100Ah battery.
- 0.9 is the usable depth of discharge. A LiFePO4 battery can safely use about 90% of its rated energy, against roughly 50% for a lead-acid or tubular battery.
- 0.92 allows for inverter losses. The inverter turns DC battery power into AC power and loses some energy as heat while doing it.
- watts is the total load running at the same time.
So each 1 kWh of LiFePO4 gives you about 828 watt-hours of real power at the socket. If you prefer not to do the maths, use the backup calculator (Battery Backup Calculator).
Backup time table for common battery sizes
These figures come straight from the formula. Loads are typical Pakistani home loads:
- 12V 100Ah (1.28 kWh): 100W (1 fan + 2 lights) about 10.5 hours; 300W about 3.5 hours.
- 24V 100Ah (2.56 kWh): 300W about 7 hours; 450W about 4.7 hours; 920W about 2.3 hours.
- 5kW class, 51.2V 100Ah (5.12 kWh): 300W about 14 hours; 450W about 9.4 hours; 920W about 4.6 hours.
- 10kW class, 51.2V 200Ah (10.24 kWh): 300W about 28 hours; 450W about 19 hours; 920W about 9.2 hours.
- 15kW class, 51.2V 280Ah (14.3 kWh): 450W about 26 hours; 920W about 12.9 hours; 1,300W about 9 hours.
- 16kW class, 51.2V 314Ah (16.07 kWh): 450W about 30 hours; 920W about 14.5 hours; 2,000W about 6.7 hours.
Here 300W is 2 fans, lights and a fridge; 450W is 4 fans, 8 LED lights and a TV; 920W is a 1 ton inverter AC with a fan and lights. Browse by size: 5kW batteries (5kW Lithium Battery), 10kW batteries (10kW Lithium Battery) and 16kW batteries (16kW Lithium Battery).
How to add up your load in watts
Write down everything that will run together during load shedding or at night, with its rough running power:
- Ceiling fan: about 70 to 80W (DC or inverter fans use less).
- LED light: about 10 to 15W each.
- LED TV: about 80 to 100W.
- Wi-Fi router: about 10W.
- Refrigerator: about 150W on average, because the compressor switches on and off.
- 1 ton inverter AC: about 800 to 900W when cooling hard, lower once the room is cool.
- 1.5 ton inverter AC: about 1,200 to 1,300W when cooling hard.
Add them up and use that total in the formula. Appliance labels show the maximum, so your real load is often a little lower, which means slightly longer backup.
Why real backup can be shorter
The formula is a good estimate, but a few things change the result at home:
- Start-up surges: fridges, pumps and non-inverter ACs pull a big current for a second when they start. This does not use much energy, but a large surge can trip a small battery's BMS.
- Inverter idle draw: the inverter itself uses some power even with no load. On a light night load this matters more.
- Heat: in a hot store room the battery and inverter both run less efficiently. Keep the battery in a shaded, ventilated place.
- Low-cut setting: if your inverter cuts off at a high voltage or a high SOC (state of charge), you use less than 90% of the battery. See the settings guide (Lithium Battery Settings for Growatt, Deye, Inverex and Knox).
- Age: after thousands of cycles a LiFePO4 battery keeps most, but not all, of its original capacity.
Backup for a 1 ton or 1.5 ton AC
Air conditioning is the load most Pakistani buyers ask about. A 1 ton inverter AC with a fan and lights (about 920W) runs for about 4.6 hours on a 5kW lithium battery, about 9 hours on a 10kW battery and about 14 hours on a 16kW battery.
A 1.5 ton inverter AC at full cooling (about 1,300W) roughly halves that. For one AC through a full summer night, most homes need the 10kW to 16kW class. With solar panels charging the battery during the day, the battery only has to cover the evening and night. For AC-focused picks see lithium batteries for AC (Lithium Battery for AC).
Worked example: a typical 5 marla home
Say load shedding or night use covers 4 fans (about 300W), 8 LED lights (about 100W), a TV (about 90W), a router (10W) and a fridge (about 150W average). Total: about 650W.
- 5kW battery (5.12 kWh): 5.12 x 828 / 650 = about 6.5 hours.
- 10kW battery (10.24 kWh): about 13 hours.
- 16kW battery (16.07 kWh): about 20 hours.
If you add a 1 ton inverter AC for part of the night, add about 850W for those hours and work out the energy separately. The backup calculator does this split for you.
How to get more backup from the same battery
- Use inverter ACs, DC fans and LED lights. Cutting the load from 450W to 300W gives about 50% more hours.
- Set the AC to 26 degrees instead of 18 to 20. The compressor works far less.
- Run the water pump and iron while solar or grid power is available, not from the battery.
- Check the inverter's battery settings so it does not stop early.
- Add a second battery in parallel later. Most 48V wall and rack batteries support parallel connection; check the maker's sheet for the maximum number of units.
