If a solar panel has a power rate of 80 Watts and efficiency of lets say 30%. Does that mean the maximum power this solar panel can generate is (30/00)*80=54 Watts or its just 80 Watts?
If it says STC or Standard Test Conditions on the nameplate or documentation, then that means 80 watts under bright sun at an unrealistically cool temperature. It is rare to see that power in real life, except when the perfect storm of conditions come together. There is also a PTC rating for some panels, which is more realistic. If the panel does not say STC or PTC, the manufacturer is free to make up whatever test they feel like, which generally leads to ridiculously overstated power. As for efficiency, for residential panels, that's generally only of academic interest. A 80-watt panel is 80 watts, regardless of the efficiency. A more efficient panel will take up slightly less space, but most people are more interested in the total price, since roof space is generally not an issue.
Solar panels are tested in a lab that has a light the produces 000 watt/hrs per square meter. In these conditions your panel will produce 80 watt/hrs. If you would like to know what it does in really world conditions you have to find the sun-hours in your given area. A sun-hour is basically how many watt/hrs hit a square meter in a day. This number changes based on time of year, orientation, and temperature. Here in Fairbanks Alaska if the panel was at 90 degrees facing true south in October (.9 sun-hours) It would produce 80 X .9 X .8 (20% efficiency loss due to wires and controllers) it would produce 273.6 watt/hrs on average each day.
