Off Grid Solar System Sizing Calculation depends upone various factors whic are below.

**The controller algorithm**

Controller’s Voltage must be the same with the off grid inverter, same with solar panels voltage output level after it connected. Then start to Calculate the current:the current is decided by the solar panel’s power,for example: four 200W solar panels,total 800w . the output voltage level after the connection is assumed to 24V, that current is 800/24 = 33A, which is greater than 33A, charge controller, we can choose 24V / 40A of the charge controller.

emphasized: the size of the controller is determined by the solar panels; that is power of charge controller (voltage * current) is bigger than or equal to the total power of all photovoltaic panel;

**Off grid inverter Algorithm**

Inverter size is determined by the load, that is it is decided by back of the equipment loaded, but the device is divided into inductive load And resistive load, inductive load refers to motors, fans, pumps, air conditioners and other open opportunities for moving equipment, these devices will be turned on 4-7 times inrush current (except frequency start, frequency conversion has no effect), when calculating those devices, at least as 4-fold Power to calculate; resistive load refers to open little or no impact on current, such as lights, computers, monitors, etc; these devices will be able to calculate the original power.

When choose the off grid inverter , inverter’s power is bigger than the amplified load power;such as with 1KW pumps and a 1KW computer, that there will be more than four times the impact of water pumps, the computer does not.it would have to have a maximum power of 4 + 1 = 5KW, so at least choose the 6kw inverter

**Battery A****lgorithm**

Battery selection also depends on power and time duration of the back of the device; power is sum of the load, but do not count the impact, because the impact of the boot just a very short time, little effect with the battery; the equation :(the total load power/ DC voltage) * time = single battery capacity; the number of battery section = DC voltage / individual cell voltages; For example: loaded withA 1KW motor, a 1KW computer, two hours to the emergency power supply, that the total power is 2000W, if the DC voltage is 24V,Individual cell voltage is 12V; battery capacity = (2000/24) * 2 = 166, which is to use 180AH / 12V battery; the battery section Number = 24V / 12V = 2; so this case will use section 180AH / 12V battery 2;