How does an off-grid solar power system work?

There are 4 basic components to an off-grid solar power system: solar panel array, charge controller, inverter, and battery bank.

The solar panel array is rated in Watts (W). The size of your panel array determines how many watts are going into your battery bank. Generally speaking you want to have your panel array large enough that you can recharge your battery bank in 4-6 hours of sunshine. For example if you have a 13kWh battery bank connected to a 3000W solar panel array the batteries should recharge in approximately 4.3hrs given that you have a perfect clear day. Any cloud cover or shading of the panels will make them take in less watts and therefore the battery bank will take longer to recharge.

The solar panel array connects to the charge controller. The charge controller regulates the voltage of the power coming from the solar panels into the battery bank. It is important to not overload your charge controller, it can damage your battery bank. Be sure to consult the manual for the charge controller you have and read the specifications for the maximum wattage, voltage and amperage that it can sustain. You can use multiple charge controllers for multiple solar panel arrays going to the same battery bank.

The inverter is what supplies you with 110v and 220v power by converting the DC power from your battery bank into AC power. The inverter size determines how much useable power you have to power devices. For example your average coffee pot consumes about 1800W when it is brewing coffee. To be able to run that coffee pot on your solar power system you must have an inverter capable or producing a minimum of 1800W. If you had a 1800W inverter and this coffee pot was plugged into it and you wanted to also plug in a blender for example, the inverter would not be able to supply the needed power to both items at the same time.

The last component of an off-grid solar power system is the battery bank. The battery bank is where the power from the solar panels is stored. That power can then be used as either DC power or AC power with the inverter. You’ll want to do an energy audit on yourself to help determine how much storage you will need. An easy way to help you figure it out is to look at your power bill and find the month that you used the most power, then divide that total by the number of billing days for that month. That number is what you would base your storage off of for 1 day. It’s recommended to have storage for 3-4 days if you live in an area that gets frequent cloud cover. You can use this Off-Grid Solar Sizing Tool from BatteryEvo to help determine the size system you will need.