For the sake of convenience, let's believe you possess a a 100 watt appliance or load that you would like to operate, free of charge through solar power, for around ten hours every night. In order to exactly determine the dimensions of the solar panel, batteries, charge controller and inverter the following mentioned. 1) First you will need to estimate how much watts of electricity you may require for the specified load. Let's say you have a 100 watt load that needs to be operated for approximately 10 hours, in that case the total power required could be estimated simply by multiplying the. 3) Once you have calculated the solar panel as per the above calculations, it's time to calculate the AH rating for the batteries that might be required for operating the specified. 2) Next, we need to determine the approximate dimensions of the solar panel for satisfying the above estimated load requirement. If we assume. 4) Now, to figure out how big your solar charge controllerwould need to be for the above calculated parameters, you might need to take your solar panel current or the Amperage specs into consideration, which may be simply gotten by dividing the panel's wattage rating with.