Daz1712:
Remember you will be working on 6 hours of sun to replace up to 72 hours (3 days) of use!
I'm used to calculating at 1:10: 1W of load requires 10W of solar panels for mostly continuous operation. Works quite well in my climate - higher latitudes may need more rated solar wattage per load wattage.
About half of the day there's sunlight, but less than half of that is at maximum strength (the hours around midday), and less than half of that is actual enough to get near rated power from the solar panels (clear sunny skies).