Nowadays, even the numbers on the specification sheets of industrial products should be taken with a grain of salt. Here is a good article on how not to be fooled by horsepower ratings of electric motors: http://www.kevinsbrady.net/motors.pdf Just one quote from it:
Take a trip through any home center store, and you will find an array of motorized tools and other devices, with their respective “horsepower” ratings emblazoned on them. This particularly applies to circular saws, routers, air compressors, and shop-vacuums, the makers of which often attaching wildly exaggerated claims of power. Obviously, “puffing” is still the norm. I have seen models of shop vacuums and air compressors boasting 5HP at 125V! If this were true, you would need a power cord as big around as your thumb to handle the current and an industrial 50-amp outlet to plug it in to! The streetlights on your block would flicker every time you turned it on!
I am reading a book ‘Solar Energy Projects for the Evil Genius’, and when it talks about flow rates of irrigation pumps I read the following:
Manufacturer’s figures can often be optimistic and sometimes unreliable. While the minutiae sometimes don’t matter, if you want to be sure and test flow rate, all you need is a gallon bucket and a stopwatch. Time how long it takes to fill up the bucket.
I think scepticism should be taught to children since very early age. It is one of the most important skills in the modern world full of creative marketing.