Calculating the energy use of a VRV250 fridge
Here is the calculation: it has a 75-watt compressor, running on a 12-volt system 75/12=6.25 amps consumption, but due to the insulation, the fridge does not run all the time. It runs about 15 minutes in the hour once cooled down, 6.25/4=1.56 amps per hour and 1.56x24=37.5 amps per day.
Depending on how often the door is opened and if you put warm things in the fridge, there will be a variation in energy use; these calculations are based on trials run in our workshop where the fridge was opened a couple of times a day, and the fridge was run empty. A full fridge will take longer to come down in temperature but once cold will maintain its temperature more consistently because of the stored cold energy in the goods
Solar system calculations must be done on worst-case scenarios, so calculate how much the solar system generates in mainly overcast conditions; for example, a 260-watt panel might produce about 15 amps per hour in full sunshine, so, in theory, you need 3 hours to make 45 amps, the fridge uses 37.5 per day, however in overcast weather the same panel will only produce a measly two amps per hour, therefore unable to keep up with the demand when it is cloudy.
That is why the battery capacity should be factored in, to buffer the supply and demand between the solar system and the fridge
Below are some links with more information
https://www.vantagerv.co.nz/blogs/rv-tips-and-information/faq-regarding-solar-refrigeration
https://www.vantagerv.co.nz/blogs/rv-tips-and-information/why-invest-in-a-solar-fridge-over-a-3-way-fridge
https://www.vantagerv.co.nz/blogs/rv-tips-and-information/common-problems-with-solar-or-compressor-fridges