When customers ask me what battery size fits a 5kW inverter, I always say—it depends on how long you want to run your system and how much energy you use. One size doesn’t fit all, especially in off-grid or backup applications.
A 5kW inverter typically pairs with a 48V lithium battery system sized between 5kWh to 20kWh, depending on runtime needs and depth of discharge. The higher your energy usage or backup time, the bigger your battery bank should be.
Let’s break it down clearly with examples and real-life use cases.
How to Calculate Lithium Battery Size for a 5kW Inverter?
The first step is understanding how long you want to run your inverter at full or partial load.
To calculate the battery size (kWh), multiply power (kW) × hours of use. Then adjust for battery efficiency and depth of discharge.
Basic Formula:
Battery size (kWh) = Inverter Load (kW) × Runtime (hours) ÷ DoD × Efficiency
Example:
- 5kW load × 2 hours = 10kWh
- For LiFePO₄ with 90% DoD and 95% efficiency:
→ Required size = 10 ÷ 0.9 ÷ 0.95 ≈ 11.7kWh
So you'd choose a 12kWh battery bank to run a 5kW inverter for 2 hours at full load.
Recommended Lithium Battery Voltages and Capacities
Most hybrid and off-grid 5kW inverters use 48V systems. Here's a quick sizing guide:
| Battery Size (kWh) | Voltage | Capacity (Ah) | Approx. Runtime at Full Load |
|---|---|---|---|
| 5kWh | 48V | 100Ah | ~1 hour |
| 10kWh | 48V | 200Ah | ~2 hours |
| 15kWh | 48V | 300Ah | ~3 hours |
| 20kWh | 48V | 400Ah | ~4 hours |
Choose based on your daily usage or backup time requirement.
Should You Oversize the Battery?
Oversizing improves performance and lifespan. When batteries aren’t pushed to 100% depth regularly, they last longer. I recommend using only 80–90% of total capacity.
Real-World Tip:
If your average daily load is 10kWh, consider a 12kWh to 15kWh battery bank. This gives a buffer for cloudy days or surges.
Series vs. Parallel Configuration for 5kW Systems
A 48V system is ideal for a 5kW inverter. You can achieve this voltage by:
- Using 15-cell LiFePO₄ (3.2V) in series = 48V
- Or connecting lower voltage modules (e.g. 24V) in series
For higher capacity (Ah), connect multiple battery strings in parallel.
Example:
3 × 48V 100Ah lithium batteries in parallel = 48V, 300Ah → 14.4kWh usable capacity
Conclusion
Sizing your lithium battery for a 5kW inverter depends on your daily energy needs and desired runtime. For most homes and small businesses, 10kWh–15kWh is a solid starting point. Always factor in depth of discharge and inverter efficiency.
SANKE provides high-quality, factory-direct LiFePO₄ lithium batteries—over 5,000 cycles, minimal after-sales needs, and true long-term savings for your system.
FAQs
What size lithium battery is best for a 5kW inverter?
A 10kWh–15kWh 48V lithium battery is ideal for a 5kW inverter, depending on how long you need it to run.
Can I use a 24V battery with a 5kW inverter?
Most 5kW inverters require 48V input. Using 24V will not work unless the inverter supports it or is reconfigured.
How many batteries do I need for 5kW inverter?
It depends on capacity per battery. For example, if using 48V 100Ah (5kWh) batteries, you’d need at least two to three for 10–15kWh of storage.
Will a 10kWh battery run a 5kW inverter?
Yes. A 10kWh battery can run a 5kW inverter for about 2 hours at full load or longer at partial loads.
