This is for one of my solar panels (I’ve micro-inverters, so I’ve data for each panel). In green the solar panel in blue the tempest. My solar panel is around 1.5m2. Note the different vertical scales used.
So for the point at 12.30, the tempest indicates a solar radiation of 475W/m2 (or so), the panel produced 175W which is 117W/m2 (175W / 1.5m2). That would imply an efficiency of 25% (117/475*100%), which would be amazing. More likely some measurement isn’t really that exact, or I’m doing something wrong.