What Size Solar Panel for a 200Ah LiFePO4 Battery?
Size solar for a 200Ah lithium bank using battery voltage, usable energy, desired recharge window and controller capacity.
A 200Ah battery bank can range from a modest 12V RV bank to a much larger 48V system, so amp-hours alone do not determine panel size.
A 12.8V 200Ah LiFePO4 bank stores about 2.56kWh, so a same-day refill after deep use often calls for roughly 600–1,000W of solar depending on sun and losses. If daily consumption is only 1kWh, the array can be much smaller because you only need to replace what you use.
What matters
- Convert the battery bank to Wh first.
- Use the expected daily depth of discharge rather than automatically assuming a full recharge.
- Target recharge time determines required array power.
- Higher-voltage battery banks change controller output current.
Decision factors that change the answer
Nominal energy
At 12.8V, 200Ah equals roughly 2.56kWh before reserve and losses.
Daily consumption
Solar should usually be sized around energy used per day, not full bank capacity.
Recovery target
A one-day refill target needs more panel power than a two-day recovery strategy.
Controller current
Larger arrays can push substantial charge current into a 12V battery system, increasing controller and conductor requirements.
How to size it
- Calculate bank Wh from nominal voltage × Ah.
- Estimate Wh to replace.
- Divide by realistic daily solar hours and expected system efficiency.
- Round up and verify controller/battery charging specifications.
A nominal 12.8V 200Ah bank is about 2.56kWh, while a 24V-class 200Ah bank stores roughly twice that energy.
Worked example
Replacing 2kWh with 4 peak-sun-hours and 80% efficiency requires about 625W of panels. An 800W array gives margin and faster recovery; 400W may need two strong days.
Common buying mistakes
- Treating all 200Ah systems as equal.
- Ignoring controller amperage at lower bank voltages.
- Planning around summer sun when winter resilience is the goal.
Panel size follows watt-hours to replace, not the 200Ah label by itself.
Check the underlying numbers
Use these site resources to replace generic assumptions with your own load or the source-linked data behind this guide.
Use the numbers before choosing a model
Start with your load list. The battery needs enough watt-hours for the desired runtime and enough continuous/surge watts to operate the appliances at the same time. Then check whether your recharge method can replace the energy you expect to consume.
For outage planning, we recommend keeping reserve capacity instead of designing a system that reaches 0% at the end of the forecasted outage.
Next step
Estimate battery runtime → or Build a critical-load energy budget →.