Quick answer: The Tesla Powerwall 3 is best for whole-home backup at a lower cost per kWh. The Enphase IQ Battery 5P is better for modular, AC-coupled retrofits to existing systems. Both are excellent choices in 2026.
Capacity and stacking
Powerwall 3 ships at 13.5 kWh per unit and can stack to multiple units. Enphase IQ Battery 5P is 5 kWh per unit and is purpose-built for stacking many small units, which suits homes with limited wall space.