Quick Answer
A family of four with an average power consumption of 5 kilowatt-hours (kWh) per day needs a battery storage capacity of 14-20 kWh to cover a week's worth of electricity, assuming a daily average of 2 kWh of energy drawn from the batteries.
Determining Daily Power Consumption
To determine the required battery storage capacity, calculate the daily power consumption of your family. A family of four with an average daily power consumption of 5 kWh, including lights, appliances, and electronics, will require a larger battery to cover a week’s worth of electricity. For a conservative estimate, assume a daily average of 2 kWh of energy drawn from the batteries.
Choosing the Right Battery Storage Capacity
For a family of four, consider a battery storage capacity of 14-20 kWh, which should cover a week’s worth of electricity. This capacity will allow you to store excess energy generated by your solar panel system during the day for use during evening hours or during periods of low sunlight. Consider using a lithium-ion battery with a depth of discharge (DOD) of 80% to maximize the battery’s lifespan.
Sizing the Battery System
When sizing the battery system, also consider the system’s round-trip efficiency (RTE), which is the ratio of the battery’s input energy to its output energy. For lithium-ion batteries, the RTE is typically around 90-95%. This means that for every 100 units of energy stored, 90-95 units will be available for use. Taking into account the system’s RTE, a 14-20 kWh battery storage capacity will provide a usable energy of 12.6-19 kWh, which should be sufficient to power your family’s daily needs.
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