Battery storage is measured in kilowatt-hours (kWh). If you want to cover your night-time usage entirely and use 11 kWh overnight, you'll need 11 kWh of battery storage. But it's smart to add at least a 2kWh buffer for backup power — in case the grid goes down. . Your primary use case should drive capacity decisions, not maximum theoretical needs. Usable capacity differs from total capacity: Lithium batteries provide 90-95% usable capacity while lead-acid only offers 50%. Factor in 10-15% efficiency losses and plan for 20% capacity degradation over 10 years. . Home batteries store electricity from your solar system or the grid for use during outages, when the grid is most expensive, or at night when it is dark. A well-sized system can keep essential appliances running, lower your utility bill and protect you from grid disruptions. Selecting the appropriate battery size depends on a number of factors, such as energy use, solar generation (if applicable) and export patterns. It probably won't last all night, but it'll usually cover the expensive evening peak.
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