This guide focuses on single-family home energy storage capacity for U.S. homeowners. The optimal capacity ranges 10-20 kWh for daily resilience and bill savings, 4-10 kWh for essential-only backup, and 20-30+ kWh for whole-home coverage. Capacity (kWh) determines backup duration and solar shift efficiency, while key factors include battery chemistry (LiFePO4 is preferred for safety and long life), system efficiency, depth of discharge, and temperature. Sizing requires measuring actual loads, calculating based on backup needs, adjusting for losses, and adding a 15-20% margin. Pairing with solar is recommended, with specific capacity matches for different PV arrays. Power ratings (kW) matter for simultaneous device use. Economics involve installation costs, incentives, and intelligent controls like Ktech’s îHEMSess. Emerging trends include lithium dominance and grid-interactive features.