Lethargic
lifeless, sluggish
trite
dry
static
hollow
Joule -- a unit of electrical/mechanical/heat energy
A four letter word starting with the letter a is able.
inquorate
thin
The answer is Choad
Waterhose is a nine letter word starting with the letter W!
There is not a SINGLE word in the English words starting with 'z' that are related to the topic energy Lynn605's answer: actually yes there is zen its religious meditation using spiritual energy