During commissioning....which you learned about above.....we use these little buggers called Load Banks. Basically it is nothing more than a giant hair dryer. It pulls power and produces heat to imitate what it will be like when the row is full of servers. We had these bad boys set up in the hot aisles for two straight weeks while we ran test after test after test.
And below you can see how we use the "hot aisle cold aisle" system as we set the laod banks up in every other row.
--T