Where can I find water heater electricity use statistics for a research paper?

Different brands will consume different amounts of electricity - also, the size of the water heater will factor in as well. I would try typing in the name of a specific brand of water heater and you should be able to get the info pretty easily.

I can think right off the bat of three possible (and likely conflicting) sources: the government tests hot water heaters and other appliances specifically for energy use. The consumer reports people do research into various aspects of appliances, including energy use. And Underwriters Laboratories do testing on appliances.

Of these "Consumer Reports", the magazine, has a good record of impartiality and a more natural interface for a researcher, being they market to people, not salesmen.