the efficientsy of most power plants is______%?
Since this is not my area of expertise, I searched Google under the key words "power plant efficiency percent" to get these possible sources:
http://www.nei.org/newsandevents/newsreleases/operatingat/
http://www.netl.doe.gov/publications/factsheets/project/Proj219.pdf
http://w1.siemens.com/innovation/en/news_events/innovationnews/innovationnews_articles/energy/computer_simulation_increases_power_plant_efficiency.htm
http://www.nmcco.com/education/facts/business/perform.htm
Use <Find> to search articles for "percent."
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search.
I hope this helps. Thanks for asking.