Sorry, but you are wrong. You would need twenty seven (27) 28 watt CFl bulbs to make the equivalent lumen output of a 400 watt HPS. in other words you would have to use 729 watts of CFL power to get the same results as a 400 Watt HPS. Even if you were to use the larger 65 watt CFl bulbs you would need eight of them to equal the 50,000 Lumen output of a 400 W HPS and 8 of them uses 520 watts. CFL is not as efficient as HPS, they put out more heat than the equivalent light output of a HPS. So in conclusion CFL bulbs use MORE electricity per lumen than HPS lights do. The exact opposite of what you heard from someone else or may have been lead to believe. Its not your fault, lost of bad information out there and much of it is perpetuated by a majority of people who just don't know any better.If you want to pay a massive power bill an HPS will do the job. If you don't use a cfl.
Oh and the sun during the early summer at high noon puts out the equivalent of 1000 watts per square meter, so say the science books.