Flat solar panel performance today in Quartzsite

On that day in Tucson the sun's irradiance on a panel pointed at the sun reached 1000 W/M 2 while a flat panel reached 700 W/M 2. So a solar panels efficiency from sunlight was 70 percent for a PWM controller.

So since these are real world measurements that include all forms of sunlight degradation and Tucson and Q are close to the same latitude it seems reasonable to me.