A Practical Guide to Calculating Home Battery
To calculate the capacity of your home battery storage, you need to gather three critical data points: energy needs, depth of discharge
For example, let's assume you have a solar battery with a 10 kWh capacity and a recommended DoD of 80%. This means you shouldn't use more than 8 kWh before you recharge your battery again. Round-trip efficiency shows how much energy the battery loses while just storing it. The higher the round-trip efficiency is, the less energy you lose.
Power and energy requirements are different: Your battery must handle both daily energy consumption (kWh) and peak power demands (kW). A home using 30 kWh daily might need 8-12 kW of instantaneous power when multiple appliances run simultaneously.
Some batteries offer just 3–5 kW of power—enough for lights, a fridge, and a few other essentials. Quality home battery systems are modular, which means that you can scale both energy storage capacity and output power based on your needs.
Ideally, house batteries should provide those 30 kilowatt-hours to ensure a one-day emergency backup. If we take Powerwall, two units would make a 24-kilowatt-hour energy bank — close enough. Hybrid solar systems are connected to the utility grid, but they also have some extra battery storage as a backup.
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