Battery Calculator
Not sure how much battery backup you actually need? Use this free solar battery calculator to find the right battery capacity (Ah) for your inverter or solar system.
Simply enter your total load in watts, how many hours of backup you want, and your system voltage.
The calculator instantly shows the required battery size so you don’t buy too small (you’ll run out of power) or too large (you’ll waste money).
How This Calculator Works
The calculator uses this simple formula:
Required Battery Capacity (Ah) = (Total Load × Backup Hours) ÷ System Voltage
We also apply a small rounding so the result is easy to read.
What Each Number Means:
| Factor | What It Means |
|---|---|
| Total Load (Watts) | Combined wattage of all appliances you want to run during backup (fans, lights, TV, fridge, etc.) |
| Backup Time (Hours) | How many hours you want the battery to last after the grid goes off |
| System Voltage | Your inverter/solar system voltage — usually 12V, 24V or 48V |
Why Voltage Matters (12V vs 24V vs 48V)
Choosing the correct voltage is important:
- 12V systems : Best for small home inverters (1–2 kW). Simple and cheap, but higher current means thicker cables.
- 24V systems : Good middle option for 3–5 kW setups. More efficient than 12V.
- 48V systems : Recommended for larger solar systems (5 kW and above). Lower current, thinner cables, better efficiency and less heat.
Using the wrong voltage in the calculator will give you an incorrect battery size.
Example Calculation
Let’s say you have a 800-watt load (a few fans, lights and a TV) and you want 4 hours of backup on a 24V system.
800 × 4 ÷ 24 = 133.33 Ah
Result: You would need approximately a 150 Ah battery (we recommend adding 20–25% extra capacity for safety and longer battery life).
Helpful Tips for Battery Sizing in Pakistan
- Always add 20–30% extra capacity because batteries should not be discharged 100% (especially lead-acid).
- Lithium batteries can be discharged deeper than tubular/lead-acid batteries.
- For longer backup (6–8 hours), consider a larger battery bank or a hybrid solar system.
- Check your inverter’s recommended battery voltage before buying.
This calculator provides estimates based on the values you enter. Actual battery performance depends on battery type, age, temperature, depth of discharge and inverter efficiency.
These results are for initial planning only. Always consult a certified solar installer or battery specialist before making a purchase.