Off-Grid Solar Battery Systems

March, 2014





Off-grid solar systems were the starting point for much of the solar industry years ago.  Now, the majority of solar arrays are connected to the grid with a relatively small percentage of those providing battery backup.  However, for certain, select customers, an off-grid system may be the right choice.  The first, and most important step when considering an off-grid system is minimizing your power usage needs.  This will decrease the system complexity and the system design.


When Sizing an Off-Grid System Consider Five Factors:

  1. Estimated daily usage and expected maximum power draw (Load/Consumption Analysis)
  2. Solar resource (Amount of Available Sunlight)
  3. Number of days of autonomy (Days of Battery Storage When There is Minimal Sunlight)
  4. Additional back-up power sources (Generators for Example)
  5. Budget


The load analysis is extremely important as you’ll likely consider further decreasing your energy requirements once you fully evaluate your costs.  When choosing appliances, energy efficient DC-powered appliances will maximize your investment and the success of the project.


Off-grid systems are somewhat similar to DC Coupled systems.  However, the inverter will not connect to the grid and the battery-bank is larger due to the need to provide power for extended time periods (a typical design is 2 – 3 days of autonomy).  It’s also important to recognize that off-grid systems will require more monitoring and maintenance than a simple grid-tied system.  Specifically, the battery systems are typically lead-acid batteries that require maintenance to maximize the system’s safety and long-term viability.  Because the batteries are used frequently, they will need to be replaced sooner than those in a grid-tied battery backup system.


An Off-Grid System is Perfect for Someone Who:

  1. Would have a large cost to connect to the grid or experiences frequent power outages
  2. Will limit their energy usage and modify their lifestyle to live within the capabilities of the system
  3. Is willing to evaluate and maintain the system


Combining a generator with your solar array will provide additional capacity to the system and potentially allow you to consider a smaller battery bank since the generator can offset the shortfall when there is limited sun.

Off Grid - Battery Article