That's interesting, for my nexus 5 (granted it's only a few days old so perhaps there is some break-in) seems to go down to 80-85% in 10-15 minutes of morning web surfing/reading.
With high brightness and a lot of active, screen-on use, it will absolutely chew through the battery (though 20% in 15 minutes is extremely excessive: For wifi browsing Anandtech found it to be among the top devices, actually beating the benchmark iPhone devices. They then removed that result from the listing pending the full review release). What impressed me most from it is the standby time which is extremely impressive, even in difficult conditions.