How many batteries do I need for a whole house solar system?

 The battery design required for the whole house needs to consider these four aspects

• Household electricity demand
• Sunshine conditions
• Battery capacity and type Battery capacity
•  System design redundancy

1. Household electricity demand: First, we need to clarify the average daily electricity consumption of the household. If there are many household appliances and the electricity consumption is large, such as frequent use of high-power appliances such as air conditioners and refrigerators, the number of batteries required will be large; on the contrary, if the electricity demand is small and only used for basic lighting, televisions and other low-power appliances, the number of batteries required will be relatively small.
2. Sunshine conditions: The intensity of solar radiation and the duration of sunshine vary greatly in different regions. In areas with abundant sunshine, such as southern Africa, solar panels have high power generation efficiency and can fully charge batteries every day, so the number of batteries required may be relatively small; while in areas with insufficient sunshine or frequent rain, such as the Pacific Northwest of the United States, solar panels have short power generation time and low efficiency, so more batteries are needed to store enough electricity to meet the electricity demand when there is no sunshine.
3. Battery capacity and type Battery capacity:
   Common lead-acid batteries, lithium batteries, etc., different types of batteries have different capacities. For example, lead-acid batteries generally have specifications such as 12V 100Ah, 12V 200Ah, and lithium batteries have 48V 50Ah, 48V 100Ah, etc. The larger the battery capacity, the more electrical energy it can store, and the fewer batteries are needed to meet the same power demand.
   Battery performance: Lithium batteries have high energy density, long cycle life, and high charge and discharge efficiency. In contrast, lead-acid batteries have low energy density and limited cycle life. If you choose a lithium battery with good performance, you may be able to achieve the same energy storage effect as a larger number of lead-acid batteries with a smaller number.
4. System design redundancy: To ensure that the family can still use electricity normally in extreme cases of continuous rainy days or insufficient sunlight, the solar energy system is usually designed to be larger. Generally, the battery is configured to meet the electricity demand for 3-5 days or even longer. For example, in areas with frequent continuous rainy days, the battery may be configured to meet the electricity demand for 5-7 days; while in areas with sufficient sunshine and less rainy weather, it may be configured to meet the electricity demand for 3-4 days.