Quick Answer
A general guideline for calculating battery storage for a fully off-grid house is to consider a minimum of 14-20 kWh of usable energy storage, assuming a 2-3 kW array and moderate energy usage. This equates to around 12-18 kWh of battery capacity, considering a 70-80% depth of discharge (DOD) for the batteries. The actual storage requirements may vary depending on specific usage patterns and efficiency of the system.
Sizing the Battery Storage
To determine the required battery storage, start by calculating the daily energy needs of the house. A typical 2-3 kW solar array will produce around 20-30 kWh of energy per day in areas with high peak sun hours (PSH). However, the actual energy usage will depend on the appliances and their efficiency. Assuming a 2000-3000 sq ft house with moderate energy usage, a typical appliance list might include a refrigerator (500-700 Wh), oven (1500-2000 Wh), microwave (300-500 Wh), and other smaller appliances. A total daily energy requirement of 30-50 kWh can be assumed, considering some energy loss due to inefficiencies in the system.
Battery Selection and Depth of Discharge (DOD)
For off-grid applications, deep cycle batteries with a high number of cycles (around 300-500) are recommended. A 12-18 kWh battery bank can be achieved using 4-6 deep cycle batteries, each with a capacity of 2.5-3 kWh. A 70-80% DOD is generally recommended to ensure the longest lifespan and minimize battery degradation. This means that the battery bank will need to store around 21-24 kWh of capacity to provide 14-18 kWh of usable energy.
Find more answers
Browse the full Q&A library by topic, or jump back to the topic this question belongs to.