It is a pretty safe assumption that a Cloud Data Center has a low PUE. The Cloud business is so competitive that the cost to run the power and cooling systems takes a direct hit out of profit margins so almost everyone should be driving more efficient systems.
How efficient are the cloud companies?
Google is easy to figure out as they quote PUE quarterly here.
GigaOm's Stacey Higginbotham had a post on efficient data centers quoting PUE.
Microsoft gave Stacey a bunch of data, but not an exact number.
Microsoft sent me a bunch of information on its PUE figures for its newest data centers which range from 1.13 to 1.2. It doesn’t disclose the PUE for all of its data centers, however.
For Amazon, there is no clear answer. Note: James Hamilton does not claim the PUE is representative of Amazon. Given Amazon will let temperatures rise in warehouses for workers, it is hard to believe they wouldn't do the same for voiceless servers.
Amazon’s data center guru James Hamilton published a presentation on Amazon last year that assumed a PUE of 1.45 for the online retailer’s data centers.