What Size Lithium Battery for My Solar System?
Choosing the battery size for a solar system comes down to your night-time load and your inverter's voltage. This guide gives simple tables for 3kW, 5kW, 6kW and 10kW inverters, explains why a small battery can trip on a big inverter, and shows why storing your own solar is worth more under NEPRA's 2026 net billing rules than exporting it.
Updated 12 November 2026
Start with your night load
Solar panels run the house in the day and charge the battery. The battery's job is to cover the evening, the night and load shedding. So size it for:
battery kWh needed = night load in watts x hours / 828
(828 is 1,000 x 0.9 usable x 0.92 inverter efficiency.) Example: 450W of fans, lights and TV for 10 hours = 4,500 Wh / 828 = about 5.4 kWh, so a 5kW (5.12 kWh) battery is close and a 10kW battery is comfortable. Try your own numbers in the backup calculator (Battery Backup Calculator) or the solar calculator (Solar Calculator).
3kW inverter
Many 3kW inverters are 24V; some (such as the Growatt SPF 3500 ES) are 48V. Check before you buy.
- Minimum (24V): 24V 100Ah, 2.56 kWh: runs about 300W for about 7 hours.
- Better (24V): 24V 200Ah, 5.12 kWh: runs about 300W for about 14 hours.
- 48V version: one 51.2V 100Ah (5.12 kWh) battery.
A 3kW system suits fans, lights, a fridge and a TV, not an AC through the night. See 24V batteries (24V Lithium Battery).
5kW and 6kW inverters
These are almost always 48V. The common choices:
- Basic: 1 x 5kW (5.12 kWh): fans, lights, fridge and TV (about 450W) for about 9 hours.
- Recommended: 2 x 5kW or 1 x 10kW (10.24 kWh): 450W for about 19 hours, or a 1 ton inverter AC with fan and lights (about 920W) for about 9 hours.
- AC through the night: 16kW (16.07 kWh): 920W for about 14.5 hours.
Current check: a 6kW inverter at full load draws roughly 6,000 / 51.2 / 0.92 = about 127A from the battery. Many 100Ah packs are limited to around 100A continuous, so one 5kW battery may trip if you run the inverter near full load. Two batteries in parallel, or a 200Ah or 314Ah pack, share the current. Check the discharge current on the datasheet. See 5kW batteries (5kW Lithium Battery).
10kW inverter
A 10kW single-phase or three-phase low-voltage hybrid (such as the Deye SUN-10K-SG04LP3) is used for homes with 2 or more ACs or for small offices.
- Minimum: 1 x 10kW (10.24 kWh), but only for a light night load.
- Recommended: 1 x 16kW (16.07 kWh): about 2,000W for about 6.7 hours.
- Heavy night use: 2 x 16kW or a 30kW class battery (about 32 kWh): about 2,000W for about 13 hours.
At full output a 10kW inverter draws about 210A from a 48V battery, so you need a 200Ah+ pack or several batteries in parallel. See 16kW batteries (16kW Lithium Battery) and 30kW batteries (30kW Lithium Battery).
Does the battery charge fully from my panels?
A battery is only useful if the panels can refill it. As a rough rule, every 1kW of panels makes about 4 to 5 kWh a day in most of Pakistan in good weather, less in winter and on hazy days. If your house uses 6 kWh in the day and you want to store 10 kWh for the night, you need roughly 16 kWh a day from the panels: about 3.5 to 4kW of panels at the very least, more for winter. Our 5kW, 6kW and 10kW solar packages (All Solar Systems) are already matched.
Why storage matters more under net billing
NEPRA's Prosumer Regulations 2026 came into force on 9 February 2026 and replaced net metering with net billing for new users. Exported units are now paid at a much lower rate, reported at about Rs 8 to 13 per unit, while units you buy from the grid are charged at your normal tariff. So a unit of solar you store in a battery and use at night saves far more than a unit you export. For new solar homes this makes a properly sized battery a better investment than before.
Why the kW label is not the inverter size
Pakistani sellers call a 5.12 kWh battery a "5kW battery" and a 16.07 kWh battery a "16kW battery". That is storage (kWh), not power. A 6kW inverter and a "5kW" battery are not the same kind of number:
- Inverter kW: how much power it can deliver at one moment.
- Battery kWh: how much energy it stores for later.
So a 6kW inverter can work with a 5kW battery, but the battery will run it at full power for less than an hour, and may hit its current limit. Size the inverter for your peak load and the battery for your hours of backup.
Quick sizing summary
- 3kW inverter: 2.56 to 5.12 kWh (24V 100 to 200Ah, or one 48V 5kW battery).
- 5kW inverter: 5.12 to 10.24 kWh.
- 6kW inverter: 10.24 to 16.07 kWh for comfortable use.
- 10kW inverter: 16.07 to 32 kWh.
When unsure, pick the battery that supports parallel units, start with one, and add a second of the same model later.
