Quick Answer
To calculate water storage needs for off-grid solar systems, consider the daily water demand, system efficiency, and climate. Multiply the daily demand by the number of days of autonomy desired, then adjust for efficiency and climate. This will give you the required storage volume.
Determining Daily Water Demand
To calculate water storage needs, start by determining the daily water demand. This includes drinking water, cooking, hygiene, and irrigation needs. As a general rule, assume a daily demand of 50-100 gallons (190-380 liters) per person. For example, a family of four would require 200-400 gallons (760-1,520 liters) per day. Consider also any additional needs such as livestock, gardening, or industrial uses.
Calculating Storage Volume
Once you have determined the daily water demand, calculate the required storage volume by multiplying the demand by the number of days of autonomy desired. This is typically 3-5 days, but can vary depending on climate, water quality, and system efficiency. For example, if you have a daily demand of 300 gallons (1,140 liters) and want 3 days of autonomy, you would need 900 gallons (3,400 liters) of storage capacity.
Accounting for System Efficiency and Climate
System efficiency and climate must also be taken into account when calculating storage needs. A system efficiency of 80% means that only 80% of the stored water will actually be used. In hot and dry climates, water demand may be higher due to increased irrigation needs. To account for these factors, adjust the storage volume accordingly. For example, if you have a system efficiency of 80% and operate in a hot and dry climate, you may need to increase the storage volume by 20% to ensure adequate water supply during peak demand periods.
Find more answers
Browse the full Q&A library by topic, or jump back to the topic this question belongs to.