[bno1]

Maybe it meant the rate of energy consumption while the servers are rendering and sending the page. You'd have to multiply 30w with the time spent by the server doing all this stuff (probably less than a second) to get the total consumed energy. A web server consuming 30w of power per connected user sounds exaggerated to me. A high-end server CPU at full load probably pulls 200w and can handle at least 1000 users.

But this is an art project and I have no idea what expertise does the artist have, and I'm not an expert either.