LiFePO4 vs lead-acid: which battery to pick for solar

Five years ago, lead-acid dominated solar storage. Today LiFePO4 sweeps it in almost every scenario. But not all. Here's exactly when each one wins.

Direct comparison

• Cycle life: LiFePO4 6,000-10,000 vs lead 1,500-3,000
• Usable DOD: LiFePO4 90% vs lead 50%
• Weight per usable kWh: LiFePO4 26-40 lb vs lead 130-200 lb
• Round-trip efficiency: LiFePO4 95-98% vs lead 75-85%
• Upfront cost per kWh: LiFePO4 $380-550 vs lead $130-220
• Levelised cost per stored kWh: LiFePO4 6-11¢ vs lead 16-25¢
• Maintenance: LiFePO4 zero vs flooded lead (quarterly checks)
• Safety: LiFePO4 very stable vs lead vents hydrogen (ventilation required)

When LiFePO4 wins (almost always)

Daily use, deep cycling, tight space, primary residence, modern hybrid inverters. The higher upfront cost is offset by far more lifetime cycles.

When lead still pays off (rarely)

• Cabin or shed with occasional use (summer, weekends)
• Very tight upfront budget (<$1,200)
• Where quality lithium and service aren't available
• Very small systems (<1 kWh)

The expensive mistake

Buying cheap lead for a primary residence because upfront cost looks lower. In 5 years the battery is done and you buy another. 10-year math always favours LiFePO4.

If you still need to pick capacity, see what battery do I need. For real lifespan see how long a solar battery lasts.